Situational Water Hammer

KarlW

Hello,

Another heating season upon us, another question:

I have a two pipe steam system my system set up with European smart valves, that other than being in Celsius, work just fine and keep my rooms at the set temperature. In this screen shot, I have two rooms calling for heat, thus turning on the boiler.

In the image my boiler is on because two valves are calling for heat (only 8 of my 15 or so of my radiators have smart valves). My problem is not with the smart system (I’d be happy to go into how this works in another discussion), but the problem of having only having 1/2 my radiators open - I get bodacious water hammer!

This does not happen when all my radiators are open, leading me to believe the water hammer is a result of what amounts to an oversized boiler when 1/2 the radiators are closed.

I have a vaporstat installed running at about 1psi with a subtractive of 10oz and it is working fine and cycling appropriately.




Would installing an F&T valve work here? I also have suspicions of a failed trap - I am ordering replacement fillers now.

Since I can’t find any good residential steam folks in Western NY, I’d love other suggestions.

Doing a rough calculation based on therm usage and heating degree days, these valves saved me something like 12% on my energy usage, and since rooms we use are heated at the times we use them, it provides better comfort all around - I’d hate to give these up.

Thanks in advance for any suggestions.

Is there any obvious solution to this problem?

Jamie Hall

Can you identify where, exactly, the water hammer is occurring? Yes. I know, finding water hammer is hard, since it telegraphs through the piping, but until you can pin it down to at least a general location it can be hard to identify the cause -- never mind the fix.

Also, when does the water hammer occur? One source of really evil water hammer on systems with valves which are sometimes open and sometimes not is water pooling -- again -- but then when the valve opens, the steam pushes the water along until it hits something (see @RayWohlfarth 's current video!). Could that be happening?

It is likely, however, to be condensate held up in some way by one or more of those valves. Normally a closed valve shouldn't cause a hammer, since the steam pipe to the valve should be pitched adequately to drain. Normally...

Without a better handle on when and where the hammer is occurring, there's no hope of fixing it -- but I doubt very very much that an F&T trap on anything is going to help one little bit. Even if you did know where to put it.

KarlW

Thanks for the feedback.

I think I have it down to two locations and I think it happens at both places. As to when it happens, its not regular in the cycle, the two times I heard it while I recorded this happened right after vaporstat shutoff and the other right before - I’ve tried turning the pressure down further, but I found it didn’t reactivate after a cold night this week.

The first is at the “corner” of the return line, where the steam line and return drop to the floor; there’s also an air vent there (see pic).




The second is past this location where a drain line drops from above (see 2nd pic). This is most likely tied to a radiator on my second floor landing - what’s interesting about this one at this radiator you can actually hear what sounds like water running through it. I have a replacement trap insert, but I need to order a new cover as well to make it work. I’ll see if I can edit and upload my videos on my computer later.

JUGHNE

Show us your boiler piping, floor to ceiling. All sides.

Especially where the water returns to the boiler.

Take note of the relationship of the actual water line level in the sight glass and the height of your return pipes. Also, the Hartford Loop, which is the jump up from the floor to where it connects to the return pipe on the boiler.

KarlW

Here we go - as best we can - my 2000sf house has an actual boiler room under the enclosed front porch so it is fairly tight:

This panoramic photo is the best "front view" I can get:


Best picture of the glass


The Hartford Loop seems quite large to me. The left side includes a dip into the dirt below the slab (the left side of the tee closer to the camera matches up to the top left of the first photo):


The return continues around the backside of the boiler behind my water heater - and includes the feed line where you can see it rising back up to the boiler:


The right side of the boiler was hard to photograph, but you can see the return meeting the drop from the right tee in the first picture:


It is 10-15 feet from the drop to the dirt to the inlet back into the boiler, and the inlet seems about 2" below the normal water level glass on the boiler it is supposed to be.

I appreciate your interest and help on this.

EBEBRATT-Ed

Try lowering your steam pressure.

KarlW

EBEBRATT-Ed said:

Try lowering your steam pressure.

This is what I just spent the last couple weeks doing, I am just barely heating my third floor radiator at the settings above.

neilc

that boiler piping is all mixed up wrong,
bad traps?
and where is your venting?

neilc

has pigtail been serviced?
post a more general picture of Ptrol and gage,
what pressure is that gage at in the picture above?

KarlW

neilc said:

that boiler piping is all mixed up wrong,
bad traps?
and where is your venting?

Can you explain how the boiler piping is wrong? - it looks fairly standard if a bit spaced out.

It may be a trap - I am awaiting parts as I have old Illinois Traps that isn’t the standard one - how can I tell conclusively.

I have two vents that I know about, both already shown: the first is in the pic a few posts above with the light bulb and the circuit breaker box - this is the furthest point from my boiler on the basement level. The second is to the right of the boiler room door in front of the light-switch boiler shut off.

neilc said:

has pigtail been serviced?

I am 100% sure the pigtail is clean and works - I had an embarrassing incident where I removed a gauge earlier with the boiler off but still pressurized - steam hissing out for a couple mins. The vaportrol also operates at its proper settings.

post a more general picture of Ptrol and gage,
what pressure is that gage at in the picture above?

The guage is a mistaken one I just purchased that caps out at 8oz (replacement due next week). It rises to its max and then drops down to about 6oz when the vaportrol kicks in again.

neilc

ok, so gage and Vstat are likely ok,

that header, Not,

as I see it, (the pictures are a little dark and vague)
the boiler riser feeds a bull head tee at header(wrong),
to the left, a main , then further to an old riser feed, turned down, plugged, and holding water.(all wrong)
to the right, a tee down to an equaliser, then another main, (3 strikes, you're out),
wet steam doesn't know what way to go cept up , up and away, there's no proper flow there.

the boiler header should be,
Boiler riser or risers, feeding the horizontal header, then any any system mains, then the turn down to an equaliser,
like this, the steam rising flows smoothly to the end of the header, pushing any wet steam condensate to, and back down, the equaliser, between the boiler risers and equaliser, nice sorted dry steam shoots up your mains,

did anyone ask, or did you say?
where are you hearing the hammering?
at the boiler? rads? somewhere in between?

mattmia2

What pressure is it at when you get the hammer, what pressure is it at when you don't? You are probably getting enough pressure for the steam to blow past the water seals at the end of the mains when much of the system is closed off. Does it shut off on pressure when it isn't happening? The solution is probably to figure out what is wrong with the vaporstat such that you can't get it down to 8 oz or so. You are turning down the differential when you change the main right? It looks like where you have it set now if you turn the main down anymore you will make the cutin less than 0. try setting the main to half a pound and the differential to about 4 oz.

What does the low pressure gauge read when there is hammer and when there isn't?(you will need to wait until you get a new gauge to answer this)

What kind of system is it? what kind of radiator valves did you have? do they all have steam traps?

109A_5

Hello @KarlW,
Here is the YouTube video @Jamie Hall spoke of concerning your situation.
BTW the horizontal part of the Hartford Loop is suppose to be a close nipple not about 8" long. Look at any boiler install manual. That can cause banging too.

Case of the banging steam pipes
https://youtu.be/dQaG6RLZ8wk

KarlW

mattmia2 said:

What pressure is it at when you get the hammer, what pressure is it at when you don't? You are probably getting enough pressure for the steam to blow past the water seals at the end of the mains when much of the system is closed off. Does it shut off on pressure when it isn't happening? The solution is probably to figure out what is wrong with the vaporstat such that you can't get it down to 8 oz or so. You are turning down the differential when you change the main right? It looks like where you have it set now if you turn the main down anymore you will make the cutin less than 0. try setting the main to half a pound and the differential to about 4 oz.

I’m getting the water hammer at “full pressure” usually after the 3rd or 4th cycle. It does not happen on the first cycle.

I’ll try 8oz/4oz today and see what happens.

mattmia2 said:

What does the low pressure gauge read when there is hammer and when there isn't?(you will need to wait until you get a new gauge to answer this)

What kind of system is it? what kind of radiator valves did you have? do they all have steam traps?

It is a 2-pipe gravity steam system. My thermostatic valves are of various models, but all purchased new post-2017. I am using Netatmo smart valves to control the opening of the valves.

All my valves have steam traps, but I suspect one or two are bad - and in fact may be the whole problem.

@neilc I wish I could find a boiler mechanic to install it right, but only about 1/3 of the HVAC companies here in Rochester will touch steam, and none of them have done much to improve my system - I certainly can’t trust them to fix it.

PC7060

Can you post a picture of the smart valve installs on the radiators?

KarlW

PC7060 said:

Can you post a picture of the smart valve installs on the radiators?

Attached is the smart valve - installed in my preferred horizontal manner so the radiator doesn't overstate the temperature.


To preempt the following question - here's the trap - this is the most common steam trap in my house.

PC7060

Thanks for posting, nice set up.
Is that TRV specifically designed for steam system? Looks like a Honeywell valve, it that correct?

One vote for another thread showing how you set up the system. Especially interested in how you dealt with the power and WiFi issue between European and US standards 

KarlW

PC7060 said:

Is that TRV specifically designed for steam system? Looks like a Honeywell valve, it that correct?

My understanding is that there is no difference in TRVs for two-pipe steam and water. This is a Honeywell - I have a couple of brands, but they are all new.

Jamie Hall

Before you do anything else, check all the traps. It's not hard. If you have an IR thermometer, check the temperature difference between the inlet and the outlet of the trap -- it should be at least 5 degrees and more is better. If you don't have an IR thermometer, you can use your hand -- carefully. The oulett should be noticeably cooler.

Try Tunstall or Barnes & Jones for trap repair kits.

mattmia2

Are those traps installed properly? Normally that is the outlet of the trap that is installed as the inlet on yours. Maybe those are an oddball design.

What valves were on the radiators before you touched them? I'm trying to figure out if this is just an ordinary 2 pipe system or if it is some specific system that has been butchered.

KarlW said:

I’m getting the water hammer at “full pressure” usually after the 3rd or 4th cycle. It does not happen on the first cycle.

Is that cycling in the thermostat or the vaporstat? It is possibly that more air is working its way out as it cycles even if it is on the vaporstat so steam eventually finds its way to the water seal and return after a few cycles but it is just air pushing through the first few times the pressure gets higher than the water column in the drip.

KarlW

mattmia2 said:

Are those traps installed properly? Normally that is the outlet of the trap that is installed as the inlet on yours. Maybe those are an oddball design.

What valves were on the radiators before you touched them? I'm trying to figure out if this is just an ordinary 2 pipe system or if it is some specific system that has been butchered.

These are Illinois 1 Outboard, 1T valves as defined by Tunstall replacements (I need the matching cover to repair these). They are original to the house as far as I can tell, but many have been replaced with standard traps in the intervening years. I’m about as sure as I can be that it is an ordinary two-pipe system.

mattmia2 said:

Is that cycling in the thermostat or the vaporstat? It is possibly that more air is working its way out as it cycles even if it is on the vaporstat so steam eventually finds its way to the water seal and return after a few cycles but it is just air pushing through the first few times the pressure gets higher than the water column in the drip.

It is the vaporstat - the boiler hits full pressure then shuts of in the middle of the thermostat calling for heat.

mattmia2

I mean the valve, on the inlet, not the trap on the outlet. Usually special systems had some sort of metering inlet valve. It should only matter in balancing in most cases if there are thermostatic traps on the outlets. Although this sounds more like a water line moved down with a new boiler so it is more sensitive to pressure thing.

JUGHNE

Just some thoughts on this situation:

If the TRV's get satisfied after the 2nd or 3rd cycle they would close tight.
Any steam left in the rad would condense to water and possibly be held within the rad by vacuum, especially if there was steam in the returns that would close the trap for that rad.

Then when the TRV opens again for heat that water is released and might meet steam in the returns.

Just something I thought of after napping.

KarlW

@JUGHNE I like this theory - if this is true, how do I solve it?

Although if heating is satisfied, my boiler should shut off. As it is still warm-ish out here, it is often only 1-2 radiators calling for heat (and then another 8 on regular gate valved radiators).

pedmec

In my opinion you have plugged returns which is why it happens on the third or fourth cycle. The condensate is stacking up in the vertical until it can get horizontal then all hell breaks loose. Tap on the piping where it connects to the returns. it might loosen the sludge.

KarlW

@pedmec

I like this theory as I have been listening this weekend, I swear it moves back in my system the longer the boiler is cycling, but seems to be at vertical drops.

mattmia2

If the water line is high enough to overcome the pressure differential between the main and the return the drips from the main to the return should stay full of air, steam can only get in to them if the water seal is lost, most likely because the higher pressure in the main has pushed the water out of them so the air in them gets pushed in to the return and they fill with steam.

If the returns are clogged you will see the water level in the boiler continue to fall as the system operates. If they are working once the system is fully hot and reaches a steady state the water level should stabilize at some lower level than when it is off.

pedmec

If you hear water sloshing around then that's a good indication of a plugged return. In one of your pictures with the main vent on top you have a low horizontal that combined with the slow returning condensate can cause your water hammer. you don't need to rise up to the return over your head, just that horizontal. my guess is if you look at the water level in the boiler compared to that horizontal on that drop into the wet return it will be close in height

PC7060

@KarlW stated the problem occurs when several of the radiator TRV are closed; would this result in excess steam getting pushed into the condensate return lines though the faulty traps causing the hammer?

KarlW

I'm now more convinced than ever that it is a trap. I had a HVAC guy over today to replace a frozen shut thermostatic valve (separate issue - I'm unequipped to deal with the hilarity if my black pipe snaps/breaks), and he listened with me to what sounds like water running through one of my radiators - his diagnosis was a bad trap.

That said, he readily admitted he's not a steam boiler guy, but my Tunstall caps and capsules should be arriving later this week so I can replace a bunch of them (I've ordered 8).

mattmia2

If a trap is bad the pipe will be very hot on both sides of the trap. You can eliminate that trap from the system by turning off the supply to that radiator.

Note that as the system runs and fills completely with steam and condensate the boiler water line will fall and drips that were just barely far enough below the water line will no longer be fare enough below the water line.

KarlW

mattmia2 said:

If a trap is bad the pipe will be very hot on both sides of the trap. You can eliminate that trap from the system by turning off the supply to that radiator.

I'm sure that's true but I don't think it is definitive. The radiator I got working today would be cold on the radiator and hot on the return as the steam filled the return line. This radiator is the "sleeping porch" radiator in the schematic below - one of the three feeds from my laundry room. Unfortunately I can't tell from the basement which exact radiator each pipe feeds.

The radiator that I heard the flowing water connects to the last radiator return. It is the angled piped in the closet picture above, but I believe it is fed from a dead-end feed.

I've attached a schematic of my basement piping with rough locations of feeds, returns, radiators, and air vents. The water hammer occurs in one of two and likely both of the following locations:

1. Where the pipe drops into the low return near the closet above
   
2. At the corner where the steam lines drops and becomes the return line (circuit breaker box picture above) - the pipe will sometimes vibrate here enough to turn on my laundry room motion sensor light.
   

Does this schematic help?

Jamie Hall

By low line, do you mean a wet return -- or a return which is supposed to be wet? Remember that a dry return must be at least that famous A dimension above the boiler water line -- but a wet return must be below the boiler water line along its full length. It sometimes happens that a replacement boiler is installed with a lower water line than the original, and the "wet" return gets partially dry -- which raises all kinds of havoc.

A return line which is steam hot either has a failed trap itself, or is being heated by a failed trap on some nearby radiator (this will also cause the radiator in question to either not heat at all, or heat very poorly). Either one needs fixing.

KarlW

I assume wet return as it is absolutely below the waterline - there’s a 4ft+ drop at that far corner where I change color.

I don’t think the new boiler was installed lower as this water hammer is situational and (at least the last few seasons) didn’t occur when the boiler needed to operate at high capacity.

RayWohlfarth

Thanks for the shoutout I appreciate it

mattmia2

KarlW said:

I'm sure that's true but I don't think it is definitive. The radiator I got working today would be cold on the radiator and hot on the return as the steam filled the return line. This radiator is the "sleeping porch" radiator in the schematic below - one of the three feeds from my laundry room. Unfortunately I can't tell from the basement which exact radiator each pipe feeds.

If the outlet of the trap is hot and the inlet is cold that means steam is coming in to the trap from the return and closing the trap keeping the radiator from venting through the return. The steam is coming from a failed trap elsewhere or a connection of the main to the return that is above the water line or becomes above the water line once the system is full of steam and condensate.

How far below the water line of the boiler is the return in this corner where the drip drops 4 ft? If the water line is right at the edges of providing a water seal getting the vaprostat adjusted to cutout at 8 oz and raising the water line of the boiler maybe 1/4 higher on the sight glass would be a good test. If that stops the water hammer then you can figure out the permanent fix.

KarlW

I am 90% positive I have a bad trap and likely more than one. But the challenge is that they are somewhat unusual Illinois Traps that need extra pipework when replaced outright. I have the replacement capsules, but I await the replacement covers.

The waterline is about 14.5in off the floor, while the boiler water line as I measured it moments ago was at 26in. So I don't think it is that.

Besides, as my Mother-in-law is staying in my 3rd-floor attic, "maid's apartment," made clear: 8oz is not enough to consistently heat her radiator. I plan on changing to a smart thermostatic, but even then, I really need to run at 1psi to get the steam up there.

I've found no appreciable difference at 1psi vs. 0.5psi when it comes to the water hammer; another piece of evidence is bad traps allowing steam to trap the water.

PC7060

Better venting will improve the heating. I don’t recall if anyone brought up venting of the mains.   Can you post a couple pictures of the end of the mains and any vents?

mattmia2

KarlW said:

Besides, as my Mother-in-law is staying in my 3rd-floor attic, "maid's apartment," made clear: 8oz is not enough to consistently heat her radiator.

8 oz is plenty to heat a 3rd floor radiator. if things aren't heating until pressure builds you have a problem with venting, either not enough venting or more likely in 2 pipe, steam getting in to the returns. The air is getting compressed instead of removed, that is why broken systems sort of work at high pressures.

If those drips are 18" below the water line then it is probably steam traps (or you replaced vapor radiator valves with TRVs and now the system is dependent on the traps, not sure if the original valves were vapor valves). You need to figure out where the steam is getting in to the returns and make sure the vents are good and you will have no problem heating the whole system at 8 oz or less. You could also put orifice plates on the radiators sized based on the edr of the radiator and the traps will become unnecessary if you keep the pressure low.

KarlW

PC7060 said:

Better venting will improve the heating. I don’t recall if anyone brought up venting of the mains.   Can you post a couple pictures of the end of the mains and any vents?

The 2 vents that I know of are pictured above - I’ve wondered if they are enough as I’ve added all the thermostatic valves - they his an awful amount, and under too much pressure, they start spitting water:

• The first in the far corner vent is in the pic with my circuit breaker - 3rd pic upload, first in a follow-on post.
  
• The second is in the pic with the return dropping into the dirt, look up and to the right of the door near my light switch shutoff.
  

@mattmia2 Steam getting into the returns is very much something that happens with bad traps right? The evidence seems quite clear here. My existing valves are all standard valves, and one of my main challenges for the first 3-5 years of home ownership was to throttle the radiator in my thermostat room to make sure my house gets better heated - something the smart valves have largely, but not completely alleviated.

mattmia2

Bad traps allow steam to pass through the radiator in to the return. generally the radiator with the bad trap will heat but it will keep other radiators from heating(if the trap is failed open).

Another option is to put orifice plates in the inlet of the radiator to limit the amount of steam that is let in to the radiator to about 75% of the edr of the radiator so it condenses all of the steam that goes in to it, it never reaches the trap. By varying the size of the orifices based on load as well as radiator size you could balance the system this way.

you have to use a vaporstat or boiler sizing to keep the pressure low for this approach to work. The amount of steam that passes through an orifice is a function of the size of the opening and the pressure so if the pressure is higher more steam than the radiator can condense can get in to the radiator. Vapor systems do the same thing with special metering valves.

How are the mains vented, do they vent in to the returns with crossover traps or do they have separate vents? I can see a number of ways the TRVs closing off radiators could be keeping the mains from venting through radiators to the returns and slowing venting depending on how the system is designed and condition of main vents and/or traps.