Best insulation for steam pipes

marciacubed

Hello, everyone. I have been perusing this incredibly helpful site for a month or more now, as the old house my husband and I bought in May has steam heat. I am trying to learn about this system and do some of my own troubleshooting. The Weil-Mclain boiler is ancient (HG-5 Series 1 if I remember right). Radiators are a combination of one pipe and two pipe vented. There was NO SIGHT GLASS on the boiler when we moved in! I am not kidding! That has been corrected.  I have been successful in unclogging air vents by simmering in vinegar...save for one which I still need to replace. Little by little I am insulating previously uninsulated or poorly insulated pipes using fiberglass products from a Big Box store. Maybe not the best stuff, but it does seem to be helping.  My bedroom is the biggest problem. I have had heat there for two brief shining moments.  The supply for my room runs up the stairwell from the cellar, through a boxed in area in the ceiling of my kitchen, through an old exterior wall, and
into the back room addition before turning again to head through that ceiling and through the floor of my room to the radiator. I shimmed one end of the radiator so it should drain the condensate. I have insulated most of the steam supply run and plan to add more inside the box. However, I can tell by how hot the pipes are when the system is on that there is a SIGNIFICANT drop in temperature as it moves through the old exterior wall cavity. I do not really have good access to that space. I have shoved pieces of foam insulation into the cracks around the pipe as best I can, but I do not think it is sufficient. Also, the only heat in that back room is a wall mounted ventless gas heater which we turn down at night, so the environment for this supply pipe is NOT friendly.  It really loses steam as it makes all these twists and turns, hopping over fittings, etc! Also, I have not come across any main venting for this leg of the house, though I can hear the radiator vent across the hall expelling air as the system gets going. I may have some issues with improper pitching of pipes, but since I have briefly experienced heat in my room, I am thinking it is the surrounding environment which is causing the steam not to make it to my room. What should I be using for insulation? How do I address the old exterior wall cavity? Can I use expanding spray foam? I am not a fan of the strong chemical smells associated with that stuff, but I would like some heat in my room! Advice and guidance much appreciated. Photos are of the box I opened up in the kitchen celing. Enclosed box to the left in pic 1 contains another leg of supply which goes to my sewing room across the hall. That radiator heats, though it takes awhile. The wall behind that box is an old exterior wall of the house.

EdTheHeaterMan

Fiberglass pipe insulation is most common. 1" thickness is most common. like the bottom picture. Stuffing insulation into tight spaces is challenging. Getting the air out of the pipes and radiators is what you need to solve first. After it works, then insulate.

Air and steam can not mix, so you need to get the air out to let the steam in. But you may already know that.. So getting the steam to find its way to the radiator is an effort in using your imagination. think like steam. High pressure goes to low pressure. So on your system 1.5 PSI will flow to 0 PSI. Air will stop the steam from pushing thru. If the air can't get out, the steam will just compress the air to 1.5 PSI and stop. Finally if there is condensation in a pipe that can’t get out (water flows down hill) then the water may be blocking the pipe, and then NO air or the steam can get by that blockage.

marciacubed

Thanks, @EdTheHeaterMan. Will it hurt to wrap another larger diameter layer around the first one?  I do not think it was really 1" thick...unless that 1" means both sides of the circle. There is space between the pipe and the old plaster and lath, but the pipe is directly against the wood framing member of the box, so I have to do something a little different there. Maybe just lots of duct tape. That fixes everything, right?

EdTheHeaterMan

marciacubed said:

Thanks, @EdTheHeaterMan. Will it hurt to wrap another larger diameter layer around the first one?  I do not think it was really 1" thick...unless that 1" means both sides of the circle. There is space between the pipe and the old plaster and lath, but the pipe is directly against the wood framing member of the box, so I have to do something a little different there. Maybe just lots of duct tape. That fixes everything, right?

No that won't hurt. But I added an edit so go back and read that again

And if Duct tape don't fix it then WD40 does

EdTheHeaterMan

After you get the steam to go where you want it to go, then insulate the pipe. Insulating a problem pipe will not get the steam to go where you want it to go.

Think of it this way, When the Dead Men installed your system, they tested it with no insulation on the pipes. When they knew there were no leaks and everything worked properly, then the guys with the insulation showed up to finish the job. Because it is harder to see the problems when they are all covered up by insulation.

EdTheHeaterMan

After your system is operating, think of using this product to get insulation in ALL the tight spaces. https://www.amazon.com/Froth-Pak-Insulation-Insulates-Penetrations-Polyurethane/dp/B098R9NM5D
The products is specified up to 240°F and off-gassing should be less than 24 hours.

Jamie Hall

As attractive as spray foam might be for that problem run, I can't recommend it. It really won't be happy at steam temperatures. It won't be dangerous -- but it will degrade.

Can you insulate the box itself? And make sure it's sealed up?

Robert_25

It sounds like the bedroom radiator is not vented correctly.  Get that solved then worry about insulation.

EdTheHeaterMan

Jamie Hall said:

As attractive as spray foam might be for that problem run, I can't recommend it. It really won't be happy at steam temperatures. It won't be dangerous -- but it will degrade.

Can you insulate the box itself? And make sure it's sealed up?

I'm not well versed in insulating steam pipes with spray foam. I was just thinking of the places where they are already enclosed on at least 3 sides and then covering them up after the foam is in place. Is the interior of the Vinyl fittings for pipe insulation just Foam insulation that you carve our to fit the fitting inside the vinyl cover. I guess if the pipe was exposed and just spray foam was used there a great chance the when it gets old it might just flake off. But That is where I would use the fiberglass pipe insulation.

I'm just asking for my own Edumakation

marciacubed

Thank you all for the feedback. I am indeed aware that air, water, and sludge will all block steam. In fact, the vent on this radiator was the first I soaked in vinegar, and it worked. When I bumped up the thermostat, the radiator warmed up. But that was back in, oh, mid-October before it really got cold. As the weather turned, I noticed my room getting colder, and no warmth was even coming to the supply at the bottom of the radiator. So what changed? I could still blow through the vent, so I did not think that could be it. I checked the radiator for pitch, shimmed it up on one end, and still nothing. I felt the exposed supply pipes at the ceiling of this old back room addition. They would be mildly warm at best. So I thought, OK, maybe they are full of water or sludge. I need to attach a photo of that bit of work. You all will love it.  I have heat in the sewing room across the hall. The supply for it is the same through most of that open box in the kitchen ceiling, and then it Ts off to the left. That pipe in that open box does not seem to be a problem (other than not being insulated) because it gets HOT! On the other side of the wall it goes through...not so much, though I had heat to my radiator yesterday morning.  When I heard the system kick on, I removed the vent from my radiator and felt and heard the most beautiful little puff of air and then a very long exhale to purge all the air from the pipe. Then it started to warm up, for I think the first time in 4-6 weeks. So it sometimes works...occasionally. I took that to mean that my work insulating pipes on Thursday actually had a positive effect! However, I understand that just because event B follows event A, that does not guarantee causation. System just kicked on a few minutes ago, pipe in the open box got hot but did not make it through the wall. System shut off fairly quickly...a short cycle? So even the sewing room did not have a chance to warm up. Bad balance, need for main venting? Photo is of the piping in the back room. It goes up through the ceiling on the left and through the wall to the kitchen on the right. The pipe gets HOT just on the other side of that wall.  MAYBE pipes in that back room are not perfectly pitched, but steam got through yesterday at least for a little while. Keeping the house at a cool 62 with bumps to 64 when I am home on my days off. I don't know if that makes any difference.

BobC

What make and model of vents are you using on the other one pipe radiators? Steam always takes the easiest path. Will that cold radiator heat reliably if you boost the thermostat up 4 or 5 degrees? If it does then maybe the thermostat is being satisfied to quickly my the radiator in the room with the thermostat.

Try slowing the vent rate down on all the other radiators to see if that gets steam to your problem radiator.

Bob

EdTheHeaterMan

You can always place the thermostat in the cold room. then the boiler will run long enough to heat that room. Then any rooms that are too hot, you can take measures to reduce the heat to those rooms. Some options might be to
1. Vent those radiators with slower vents.
2. Cover the radiators with decorative covers that restrict the amount of heat they put out
3. Turn off one of the radiators in any room that has 2 or more radiators.
4. Increase the venting capability of the slower heating radiators.
5. Move to a new home with warm air heat. Then hate the way it feels so drafty.

marciacubed

@BobC Re: steam taking the easiest path, one day I shut the vent down to the radiator in the sewing room, which is the only other rad being supplied by this leg. (The valve itself is painted open). I thought maybe that would force steam my way, but I still got nothing on that try. I will try reducing the venting on other rads, but they are on a different Main supply. But first i think I need to try shutting down the sewing room again while I still have that box open so I can check that the pipe is heating up. Will try to check air vent models tomorrow. @EdTheHeaterMan Not keen on wasting heat I am paying to create by covering the rads. They are probably from late 1800s...beautiful design.  See pic.  I DO already prefer the steam heat to the forced air I have lived in most of my life. I hear the expanding  metal, and sometimes the gentle whoosh of air being vented, but NO DUST BUNNIES BEING BLOWN AROUND! Besides, I haven't completely finished unpacking here! LOL! Re: increasing venting capability, what exactly does that mean? I have the current Hoffman 1A air vent open as far as it goes, although that is NOT the vent which was originally in here. I did a little swapping due to some other issues. Do some models of rad air vents work better/faster? Also, I still have not come across any main venting for this leg. I suppose it COULD be behind the still closed box in the kitchen, but I sort of doubt it exists at all. Thank you all so much for your input and assistance!

EdTheHeaterMan

Increasing venting capacity might be to add a vent at the end of a run to the problem radiator, so the radiator vent is not the only outlet.

Here is another method to try.
https://heatinghelp.com/assets/documents/Balancing-Steam-Systems-Using-a-Vent-Capacity-Chart-1.pdf

marciacubed

@EdTheHeaterMan I am thinking that you are right. I turned down some air vents last night, including pretty much closing the sewing room, and I think I went backwards in my result. It took two or three times as long for steam to climb the cellar stairs and barely made it into the opened access box in my kitchen before the thermostat was satisfied. Wonder how many ccf of gas I burned doing that? 

marciacubed

I did not get these photos in the order I wanted. 2nd pic shows the leg for this problem run coming from right to left off the main near the boiler. Pic 1 shows it climbing the cellar stairs. Pic 4 is a detail of the bundle of services coming up the stairs with it. I am still working on insulation there, as it is a tight squeeze. Also trying to isolate some of the copper to reduce conduction to it. Pic 5 shows my opened access box in the ceiling kitchen. I do not have any access behind the slope of the stairs to the second floor. I am certain there is no insulation there based upon everything else I have found. Pic 3 is the back room which was added, so wall to left is old exterior wall.  I am thinking a main vent at the upper right in that pic just before it heads into my radiator might be the thing to help. Am I on track here?  Thank you for the diagrams!

BobC

Do you have all the radiator are vents set to maximum? That may not be helpful, they should be set to vent proportionally by the amount of air contained within the specific radiator and the pipe that connects it to the steam main. Those with the lowest volumes wound be set down low while those with the most air would be set at a higher number.

Bob

ethicalpaul

I will try reducing the venting on other rads, but they are on a different Main supply

The steam doesn't say to itself "I'm in this main supply so I'm going to ignore what's going on over in that other one!"

There is one pressure in your system (with some local delays and fluctuation) and one main can steal all the steam from the other one if they aren't balanced.

marciacubed

@BobC No, everything is not at max venting. I have made a few adjustments, reducing it for smaller rads in bathrooms, shutting down one in the upstairs hall where it was getting just way more toasty than necessary. Backed some others from Fast to Medium, but so far I cannot tell any difference other than it taking longer to satisfy the thermostat. I will work some more on that tomorrow. Usually the steam comes up the stairwell from the cellar pretty fast, and this morning when I reopened the
Rad Vent in the sewing room, it continued on pretty quickly through the kitchen ceiling, then made its left turn to get to that room upstairs. However, while it makes that left turn, it is having a very hard time continuing straight through the old exterior wall and into the back room addition where it has to turn right before going up to the rad in my room...even when the "road is closed" to the sewing room (by shutting down the vent).  I think @EdTheHeaterMan is right that I need to add main venting at the end of that leg to make it easier for the steam to find its way there. Also, I still have concerns that the cold temp in that old exterior wall and back room could be seriously injuring...even killing the steam trying to come through. I understand that everything is trying to get to equilibrium, and that includes heat. So if that transition is stealing a lot of heat, that could be a problem, yes?

marciacubed

@ethicalpaul I understand what you are saying about the steam pressure being essentially the same throughout the system. I just keep wondering if my steam is dying in that one leg due to its environment ..microclimate, if you will...and/or lack of Main venting.

ethicalpaul

OK very good. I would stay away from the term "steam dying". You can have the steam condensing, which will cause a localized vacuum/low pressure zone which will pull more steam there, or you can have a lack of venting where the air in the pipes and/or radiator(s) is not allowed to leave, causing a high pressure zone that will prevent steam flow to those radiators.

You probably know this, but I'm stating it just in case you haven't thought about it this way before.

And yes, if there's a condition that is condensing a lot of steam fast (such as a main that goes uninsulated through a crawl space or other cold space, that can have a bad effect. Although I had all my upstairs radiator pipes in basically uninsulated walls and they were fine--it heats up the pipes pretty fast and nearly every boiler ever installed has extra capacity to do that.

marciacubed

@ethicalpaul Thank you for the input. I apologize if I am using bad terminology. I moved into this house knowing NOTHING other than that steam is the gaseous form of water, that it involves a lot of energy to make the leap of a change of state, and that things are always seeking equilibrium. I have spent a lot of time perusing this and other sites, and Dan's books are on my Christmas list! Thanks for your help!

EdTheHeaterMan

I still have concerns that the cold temp in that old exterior wall and back room could be seriously injuring...even killing the steam trying to come through.

When you get the air out faster, the steam will follow. Condensation from the pipe being cold will just act to bring more steam in there, faster to warm up that pipe. Once the pipe is steam hot (because the air is vented) then the radiator will heat up.

Once that is solved, the extra cold environment of that pipe you are concerned with will waste energy, and could amount to something, over a year's time. But you can save that wasted energy with insulation AFTER you know it is working, heating, venting air, and condensation returning, in an efficient and noise free way.

Don't put the cart before the horse. They said that a lot more, back when your system was new.

marciacubed

@BobC, Most of the air vents on my rads are Hoffmann 1A. I have a pair of Vent-Rite #1s, one of which is in the room across the hall from the non-heating rad. It is the loudest vent in the house, not whistling, but a gentle whooshing sound. I JUST discovered using the mirror test that BOTH of those Vent-Rites are not totally closing. They are leaking a little steam. So trying to think like steam here, if I am always heading first into that leg supplying the rad across the hall and I continue to have a way out there, why would I bother trying to find another exit? Am I thinking correctly here? Could THAT be part of my problem?

ethicalpaul

it could be, but probably even those leaky vents are not wide open, so they are limiting the steam flow. But yes, fix or replace the leakers. It moves just like air does, wherever it can. If you blow into a big straw and a tiny straw at the same time, they both will have flow, but more in one than the other.

And no need to apologize, I was in your shoes not that long ago! (And killing steam is an OK thing to say like when there is a pool of water in a pipe, that kills (condenses) a lot of steam, but in your case above, it seemed we were talking about both ways for steam not to get somewhere so I'm just trying to help clarity)

BobC

If it's just a very small leak that won't cause the problem your having, it sb addressed but I don't think it's the cause of your problem. If it were a large leak it cause a problem. Are these two radiators being fed by individual feeds from the basement steam main? If they are on a common pipe coming from down below the one not heating may have bad slope and have a pool of water in the horizontal pipe. Any water will condense the steam until it's all heated to steam temperature so steam will take a long time to get past it. If the vent sounds like panting that could indicate water moving back and forth because of water lying in a pipe somewhere.

Shimming both ends of that radiator might be enough to let water drain out of wherever it's sitting.

You said you had stem in this radiator a couple of times. Does this problem radiator get steam at the end of a long firing session, like recovering from a set back? That indicates it ,ight take a good amount of time to get any trapped water up to temperature.

Bob

marciacubed

@Bobc These two rads are on the second floor at the back of the house which is a late 1800s addition to original c. 1820 construction. They are supplied by the same pipe coming up the cellar stairs, run through the box across the narrow galley kitchen, and then there is a fork in the road. The sewing room supply (which works) turns left, and my bedroom supply goes through an old exterior wall to the back room addition where it makes a turn to get to my rad. There are photos with an earlier post. Should I attach them again? I have considered that I may have a blockage, but I have gotten steam at least twice. The latest was late last week. That was after I had added more insulation. But maybe I had also jostled pipes enough to drain a pool of water? These two branches have parallel drip returns. Is that the right term? I checked the exposed piping in the back room again his morning, and the return for my rad is NOT draining toward the boiler. The pipes are in an L configuration, and there are no hangers. I do not know if I have enough flexibility to manipulate them. Can I try using zip ties as temporary holds? Re: a panting sound, I DID notice this morning the sound of a faint heartbeat coming from the rad in the sewing room. I thought maybe it was the sound of the steam and condensate bumping into each other. It was the first time I turned the thermostat up a little higher to see what would happen. That is when I discovered the leaking air vent...because it was still making noise when the rad was completely hot all the way across. At the usual 64, the thermostat is done calling for heat before it completely warms, so I had not noticed it before. So it would appear I have a bigger problem with pitch than I first thought.

BobC

If the common feed to these two radiators comes to a tee with one radiator being fed from on arm of the tee and the second fed from the other end of that same tee one side will have some slope and the other will be a sloped the other way. Steam will find it's way to lower pressure no matter what but water will pool in any low spot and I think that is your problem. Steel piping is rigid but over it's length there is some flex. You have to find a point at which both ends have just a little slope so water can find it's way back to boiler and stop collapsing or blocking your steam.

If you lift the entire radiator up and shim both ends you can give that feed dome slope but if you go to far you will lose whatever slope the other radiator feed has. Do you have any idea how long each radiator feed from that Tee is? Try lifting the problem child up with a 2x4 and fulcrum and slide a 3/8 or 1/2" shim under each side, I cut stats from plywood of different thicknesses to use as shims. Be gentle with the lifting and don't force anything.

You may find that fixing one radiator moves the problem to the other, you have to find a balance that works for both. Old houses move over time and things that were once level get out of level as things sag. You can use anything to test what happens as you manipulate a pipes slope if it's exposed to view and then figure out a permanent solution to keep the pipe in place when you find the solution.

Bob

marciacubed

@ BobC, Well, I do not know if I should consider this progress, but here goes. Yesterday I spent several hours slightly shimming the dry returns for these two rads in the exposed box in the kitchen and trying to correct the pitch of the return for my rad which is at the ceiling in the back room. It was all I could do to coax varying layers of corrugated cardboard under the ones in the box, as they lie directly on top of the bottom frame members of said box. The one in the back room is even worse, hanging in an L shape below the steam supply with no hangers. I used a long heavy zip tie in one place attaching the return to the supply in an effort to get some slope back to the boiler while hoping I was not creating a different low spot. Kind of hard with the L and little flexibility. 

Today was very mild and rainy, and I did not really need the heat, but I had stopped at my local plumbing supply for a few new air vents and wanted to test them, so I turned the T-stat up to 64. I was actually shocked when my rad started venting air...pretty quickly, in fact! And mind you, it did not have anything to do with the vent itself, as I had been testing at times with the old one entirely removed, making as big of a vent as I could out of the hole!

I went back downstairs to check the temp of the supply for my rad in that back room, and it was getting hot!

Now for the bad news...unless we call it good that I am learning something. I heard some significant water hammer at my rad as well as gurgling, and while the supply got hot, the radiator itself did not. So I know it is blocked in spite of the fact that I corrected the pitch several weeks ago. That was one of the very first things I checked. What does this mean? Sediment build up blocking the condensate from exiting? Is there anything I can do to coax it out of there? Would it cause damage to use an air compressor to try to dislodge crud? 

I understand about old houses settling, but it seems like someone forgot to design some pitch into this part of the system!

Thanks so much for your help!!!

BobC

You mentioned dry return a couple of times now, is this a two pipe vented radiator (a pipe on each side of the radiator)? Are the other radiators piped the same, two pipes with a vent?

Or is the second pipe a drip that was put there to solve a problem in the piping as it was installed? The fact you got steam to move down that pipe tells me you got some of that water to drain out of the pipe it was sitting in and is letting the steam by. The problem now is there is still some water sitting in a pipe and the steam is slugging it back and forth causing the hammer. i don't think it's sludge, I think it's water.

Bob

marciacubed

This particular rad is one pipe but with a short drip leg to a dry return. I have two pipe vented rads elsewhere in the house. This morning the supply got hot up to and maybe partially beyond where it heads up through the back room ceiling. My radiator did NOT vent, nor did the supply get hot above my bedroom floor. See pic.  I was concerned about creating a new low in the supply when i put in that zip tie,  but i did not know how else to get some slope on the return. It is easy enough to remove to test what happens without it. It is a new record to have that supply heat up two days in a row, so i hope that is progress even if not yet resolved. What do you think i should do next?

neilc

that supply and return,
are they straight up thru the ceiling and floor above, to the radiator?
can that rad be lifted up at all ?

marciacubed

Yes, I believe that supply goes straight through the ceiling/floor to the radiator. I have gently rocked it just to get shims under the legs on the one side.  With help I MIGHT be able to do a little more. How much pitch should it have?

neilc

more pitch, more better , , ,
looks like the pipe can rise about a 1/2 inch, till the tee coupler meets the ceiling, and that there's room with the insulation also,
grab the increased pitch there that you can,
try lifting the rad by the 1/2 inch, and shimming both ends,
you already know you want the vent end of rad slightly higher than the supply valve end,
then take another look at your ziptie corner, hard to be sure from the picture, and the insulation, but the return 90 might be a bit too high at that corner,
you'll want to eyeball that again once and if you get that rad up what you can,

marciacubed

@neilc, "more better" brings back memories of living in PA, which I just left in May!  I removed the zip tie, as I think you were right about it being too high in comparison to the T with the supply. I also made just a tiny addition to the shim of my rad, planning to do more when i have some time. I heard my rad venting right before going to bed and again when I was awake in the wee hours. Still no heat, but at a cool 62, the T-stat may have stopped calling for heat before the steam made its way all the way through to me. I can slow down that living room rad, but I also have no main venting on this leg, so it seems like I have multiple issues. Where would I put it since there is no extra headspace with this piping right at the ceiling? I will check what happens when I bump heat up a little in the morning. Thanks for your input!

neilc

if you follow your dry return back to the boiler,
there is no main venting there? picture?
any spot at the boiler, or along the way, to add a vent on the return(s)
or,
add a second, fast vent, at the rad, on the supply valve end,
picture of valve end of rad, we're looking for a vent boss,

Peter Rozano

Is there a valve to the radiator? Sometimes they fail

davevarga

First, as a landlord w a multifamily in this 100 year old hse, 'I feel your pain'. Secondly I am not qualified to address the totality of your situation. But I can make two statements that might be of help. 1. First is the vent, over time they have to be replaced. And that way of checking them when not hot, giving a quick blow in either via reverse direction or from the threaded end has been a dependable way to quickly spot a blocked vent. But not always. I had one Varivalve situation where I blew into it and it seemed fine. But knowing that the air pressure should be around .2 to .5lbs I then revisited that vent (that was not hot at the time, and wrapped my lips around the threaded end) and blew into it very gently, and it was blocked! Thus solving countless hours of thought and actions and having my local heating person weighing in and basically just shaking his head and saying he was sorry not to be of help. 2. You are the only other person I know who busted out a wall to insulate the steam pipes. I did it in one area in this lathe and plaster house. I busted out a section in the middle. Then got the fiberglass sleeve insulation and cut it into 1' sections. Put the first one on the pipe and fashioned pull ties gently around the first section. Then pushed it up about a foot. Then did another section, and pushed it up as well, thus also pushing up the first section. Kept doing that going up to the ceiling and then down to the floor. Then sealed up the hole. Thus insulating the pipe behind the wall without tearing out the wall from flr to ceiling. Hope any of the above might help you. Best... Dave

philsego

Fiberglass is carcinogenic - read this. Unfortunately, most heating professionals seem to be unaware of this.

There are some brands of high temperature pipe insulation that don't use fiberglass. I like K-Flex Titan. It's easy to work with, reasonably priced, and won't kill you.

weatherman

I guess I agree with the Heaterman.
Since it sounds like your bedroom radiation is the furthest away from the boiler in terms of distance, coupled with the number of fittings and piping to get to the radiation, you may need to help it out a bit with a little more pressure at the boiler and cutting down on the venting controls at the other radiators (sort of balancing the flow)
Yes insulation will definitely help to lessen the drop in the branch temperature but you still need to increase the flow to the furthest zone but cutting back on all of the previous branches.
I would start with shutting off zones nearest the bedroom till you get an increase flow to it.
Then its a matter of opening the zones you isolated but throttling them.

Johnt

Not the total solution to your issues but I've resolved a blocked drain line and have insulated pipes by thinking "outside the box". If the siding of your house allows (not brick), remove a section of the outside shingles/siding to expose the inside of the house. I've exposed a couple of sections of siding and replaced the tub/sink drain from the second floor and also insulated pipes that were run along an outside wall. In the old days, contractors assumed heat loss from the interior will keep the pipes from freezing but with lower interior temperatures I still had pipes freezing on the coldest days. Instead of demo'ing interior surfaces, I swapped out the lines and insulated and replaced everything in several hours. Just a thought.