Water hammer around early mid cycle, some thoughts and questions

RedChops

I just bought and moved in to this 100 year old, two-pipe steam heated house in October. For the most part, the heats great! Except about maybe 1/3rd of the way through an average cycle (several radiators already getting hot), I get a couple of minutes of some good gnarly water hammering. This goes away for the rest of the cycle once its worked out its pent up aggression. The hammer is only on one side of the house (one of the two mains), and only on the second and third floors.

So for starters, I know that the near-boiler piping was done incorrectly. Typical bad install job - they piped it riser - take off - take off - riser - equalizer; I'm getting that wet steam without question and I plan on getting it repiped this summer. Secondly, two radiators in the hammer zone - one on the second floor, one on the third, but not stacked over each other - heat so slowly that only the top of the first fin takes any heat by the time the boiler shuts down. Additionally, the supply pipe to those radiators heats up about that slowly as well. Their neighbors in adjacent rooms heat up regularly. Curiously, the third floor non-heating radiator has an air vent installed which does hiss with air the whole cycle. And for the final most curious thing - I can hear a sort of water sloshing sound from .... somewere near the non-heating radiator on the 2nd floor. No radiators appear to be full of water, I gave most of them a good shakedown.

I'm thinking, this has to be radiator steam trap related, right? All of the traps except the one attached to the radiator with the air vent are old and labeled "Jas P Marsh Reflux Jr", all appear to be 1/2". Mr. Air Vent Radiator has some other brand of thermostatic trap which appears to be older. I've pulled the caps off of a handful of traps, including the non-heating radiators and their neighbors, and they're all in the 'open' position, though one of them that is mysteriously piped in from the wall was full of rust and I had to clean that out (that radiator heats, and appears to condense normally). So if anything, I have a thermostatic trap that's stuck open somewhere.

So how should I go about tracking this down? I have a Fluke IR thermometer, though I've been playing around with the emissivity on it since some of these pipes are painted, some aren't, haven't found the sweet spot yet. I've heard some people say that it's sufficient to check the inlet and outlet temps of the steam traps, and some say that this wouldn't work because of flash steam and the temperature of the condensate. I could try a thermal camera, but I've heard mixed opinions for the same reasons. I'm also a bit unsure of what temperatures I'd be looking for, especially if there's only bound to be a couple degree difference in a working trap.

Or maybe I'm chasing down a windmill here and it truly is just the wet steam that's the culprit?

Jamie Hall

First off -- don't worry about flash steam. That is a problem -- but only for higher pressure systems. Residential, no. Not to worry.

Now... probably not a trap related problem, although there's no harm to checking the traps. What you are describing is almost always a supply pipe somewhere along the way to the non-heating radiators which is trapping water, or just may be too small -- or both. What happens is that as the steam rises to that point, but hasn't gotten there yet, it's condensing like mad in the pipe and, if the pipe isn't sloped enough or is too small, instead of being able to make its way back down to the main as it should, it gets pushed along to an elbow somewhere and goes bang. Usually it does go away as soon as the steam makes it past the problem, as the condensation in the pipe drops way off. Sometimes, though , if the problem is bad enough, enough condensate will remain to throttle the flow to the radiators.

Much easier to describe than to find... !

On checking the traps -- it is quite sufficient to check the inlet and outlet temperatures. Perhaps even more encouraging, it's a temperature drop that you are looking for, rather than the absolute temperature -- which makes the emissivity thing much easier to cope with.

neilc

so you know the near boiler piping is, off,
what about your pressure, while it's been running, what are you seeing on the gage?
have you serviced the pigtail?
and the water in the sight glass, does it bounce more than a 1/2 inch when boiling?
is it dirty?
a quick picture of the glass and pigtail and Ptrol, maybe we see something there,
dirty water makes for wetter wet steam.
and what do you have for main venting down there?
you want to max main venting out so rads don't have to struggle with a lot of air.
then, you say traps, and rad vents, which is possible, are they all like that?
post a picture of a vented trapped rad.

RedChops

Jamie Hall said:

First off -- don't worry about flash steam. That is a problem -- but only for higher pressure systems. Residential, no. Not to worry.

Now... probably not a trap related problem, although there's no harm to checking the traps. What you are describing is almost always a supply pipe somewhere along the way to the non-heating radiators which is trapping water, or just may be too small -- or both. What happens is that as the steam rises to that point, but hasn't gotten there yet, it's condensing like mad in the pipe and, if the pipe isn't sloped enough or is too small, instead of being able to make its way back down to the main as it should, it gets pushed along to an elbow somewhere and goes bang. Usually it does go away as soon as the steam makes it past the problem, as the condensation in the pipe drops way off. Sometimes, though , if the problem is bad enough, enough condensate will remain to throttle the flow to the radiators.

Much easier to describe than to find... !

On checking the traps -- it is quite sufficient to check the inlet and outlet temperatures. Perhaps even more encouraging, it's a temperature drop that you are looking for, rather than the absolute temperature -- which makes the emissivity thing much easier to cope with.

The thought had crossed my mind that there was an issue with steam getting stuck in the supplies, though you're right, much harder to find! I'll give a shot at adjusting the radiator pitch a bit to see if I can adjust the pitch of the supply on the second floor. I can't quite tell what the ordering is on the radiators, since the supply seems to come up in the center of the house on the sides.

neilc said:

so you know the near boiler piping is, off,
what about your pressure, while it's been running, what are you seeing on the gage?
have you serviced the pigtail?
and the water in the sight glass, does it bounce more than a 1/2 inch when boiling?
is it dirty?
a quick picture of the glass and pigtail and Ptrol, maybe we see something there,
dirty water makes for wetter wet steam.
and what do you have for main venting down there?
you want to max main venting out so rads don't have to struggle with a lot of air.
then, you say traps, and rad vents, which is possible, are they all like that?
post a picture of a vented trapped rad.

Pressure is very low, in a full regular cycle she wont get above around 8oz. I have a vaporstat (two actually) and have set it up at a low pressure too, but the boiler would pretty much only reach that on setback recovery. Boiler usually hangs out at around 2oz once it gets going up until the end of the cycle. My novice mind thought the low pressure was unusual, but I replaced some very leaky radiator valves and there's no steam coming out of anywhere I can see so... who knows.

I had a very reputable company come out to service the boiler - pigtail blown down, sight glass cleaned, boiler flushed, whole 9 yards. Water in the sight glass bounces a decent amount. If I start the boiler filled maybe 1 - 2in down from the top, the level will drop to a little over LWCO level for a couple minutes before slowly rising back up. Before I replaced the valves, the LWCO would typically cycle once during the first part of the heating cycle. Water quality is....average-ish, a little cloudy but better now than before for sure.






Main venting - not great. There is one main vent which seems like it might be undersized on the beginning (end?) of the dry return, before both the steam supply and dry return drop down to another equalizer with a check valve separating them. I'll take a picture, this one is weird to describe.


I opened that check valve - it's a basic one, but correctly pointed to allow water and not steam. The check valve horizontal has a small amount of standing water, it seems to be right at the boiler water line. Not sure if that comes in to play.

All rads have a thermostatic trap, one rad also has an air vent. Coincidentally, the one rad that has an air vent is one of the two that are cold - my guess is the air vent was somebody's "solution" which didn't work long term. I've sat with this one through a cycle, only air moves through the vent, no water or steam (though it doesn't really heat, so not surprising)

RedChops

Here is a little video of the sight glass maybe mid to late cycle. Note that cold I have this filled to maybe 1.5 to 2 inches below the top
https://imgur.com/a/rJZWvvg
At startup, it'll raise a bit, but never goes above the top valve at least

EBEBRATT-Ed

@RedChops

One of the issues with 2 pipe steam is a funny one. So you have 2 radiators in adjacent rooms called 1 A and 1 B.

A heats fine and B is sluggish or doesn't heat at all, so you think the problem is B, naturally.

But if A has a bad steam trap failed open it will heat great, but by too much steam going through it over pressurizes the return to B and the condensate in B can't drain and causes it to not heat or hammer

nicholas bonham-carter

It looks like your boiler piping could be shooting lots of water up into the supplies, and that may account for the excess water hammer in the supplies.—NBC

neilc

is that water that dirty?
or is it treated with purple?

if it's that dirty, and bouncing like you say, you ought skim, a lot,
then dump the sump and wet return(s), and refill with clean and run,
then do it again till water stays clean

RedChops

EBEBRATT-Ed said:

@RedChops

One of the issues with 2 pipe steam is a funny one. So you have 2 radiators in adjacent rooms called 1 A and 1 B.

A heats fine and B is sluggish or doesn't heat at all, so you think the problem is B, naturally.

But if A has a bad steam trap failed open it will heat great, but by too much steam going through it over pressurizes the return to B and the condensate in B can't drain and causes it to not heat or hammer

I've been checking the temperature diff on traps around the rads. Did end up finding one seemingly failed one (temp diff of about 1 or 2 degrees), but most of the rads don't reach steam temp all the way through. I'd live in a sauna if they did! I think I'm on to something there though, turning that rad down did help a little bit.

nicholas bonham-carter said:

It looks like your boiler piping could be shooting lots of water up into the supplies, and that may account for the excess water hammer in the supplies.—NBC

That's my biggest concern really, since that's probably the one thing I couldn't really fix till the end of heating season.

neilc said:

is that water that dirty?
or is it treated with purple?

if it's that dirty, and bouncing like you say, you ought skim, a lot,
then dump the sump and wet return(s), and refill with clean and run,
then do it again till water stays clean

Well, the bottom inch of the sight glass is a bit dirty itself, but I skimmed a good deal and drained out a couple small buckets of completely brown water. Did that until the water in the bucket was pretty much clear. I was skimming kind of regularly (I'd usually try to do it right before a cycle would start so the boiler wouldn't be as screaming hot) just a small amount each time, but no matter how much I did it, the same amount of gunk would come out. Not sure if the lines really just have that much grime caked in them, or if it's regular iron oxidization. The color of the water during these skims ranges from coffee to hot chocolate. I stopped really doing it because I got worried about introducing so much fresh water in to the system. Just a bit odd, because when the boiler is idle the water looks pretty clear in the sight glass like a lot is settling below.

ethicalpaul

With my old boiler, no matter how much I drained or skimmed it, it would eventually make the water hot chocolate colored again. When I took it out of commission this fall I found out why-- there was just tons of "mud"/iron oxide/flakes in every nook and cranny. I believe the boiler had minimal maintenance for a couple decades.

I would say don't obsess about it, but keep draining some of the muddy water periodically and you may eventually "catch up" and have an actual clean (enough) boiler.

As an example, when I removed the ports such as the gauge glass brass fixtures, I found a huge buildup of sludge behind them.

ruben356

I am having similar issues with my boiler, and Skimming is the next troubleshooting step i am currently at. Waiting for a 2 1/2" Hex bushing from Grainger, so i can setup my skimming piping as it was never setup. My boiler was installed 2 years ago, so this possibly tells me they never skimmed. I noticed recently my water level also surging way too much so I am hoping this will fix it.

It's interesting though, my parents have a steam boiler probably replaced around 2008, and we just do a basic flush after and before heating season, and they haven't had any issues remotely close to what i have. Maybe there's something in our water, i am thinking of installing whole house filtration system next, also have staining tub issues, not sure if these water chemicals can cause issue in the steam boiler.

EBEBRATT-Ed

@ruben356

Unstable water line is do to 1 of two things usually. Dirty water (skimming) or improper near boiler piping

ruben356

EBEBRATT-Ed said:

@ruben356

Unstable water line is do to 1 of two things usually. Dirty water (skimming) or improper near boiler piping

Yes, i do have a thread created and getting great suggestions. My piping is not ideal (copper header, undersized) but usable, i will be re piping after this heat season is over. I am trying skimming now since its something i can do during the cold and won't take up too much time. I am more hoping the skimming helps quiet doing the hammering and surging.

RedChops

So where I'm at right now is I have a bunch of new pipe hangers coming on Tuesday from Supply House. On the side of the house that knocks, I can visibly see that the 2.5" main appears to slope back towards the boiler for a bit before it starts sloping back to the return. I'm guessing that when the asbestos abatement happened, the knuckleheads didn't actually take a level to the pipes to make sure the pipes were hung back to the proper pitch. There might even be a sag in there, but I wont be able to tell for sure until I get that insulation off and check with my level. They're hung with iron bands, so I'm replacing them with something a little nicer. The 2.5" mains are all insulated, but I'm planning on insulating the 2" takeoffs that go to the second and third floors too since they're currently fully exposed. I have to find that fiberglass mat insulation so I can insulate the tees as well since those are exposed everywhere.

My skim port has been capped off so I need to figure out what hardware I'll need to make a usable service port out of it. Given that almost nothing on this boiler was installed according to the manual (near boiler piping in the picture above, all of the cutoffs were wired in some weird series including the thermostat only using the transformer for the primary coil, ignoring the rest), I doubt this was ever skimmed properly.

clammy

I didn’t read through all your posts but your mid cycle hammer on a 2 pipe could be ,return being pressurized from bad traps , I see your boiler is not pipe correctly and are your end of the steam main and dry return tie together below the water line forming a water seal very necessary . Aside from the mid piping of the boiler the lack of insulation on your steam mains does nothing to help your issues . Change out the dry return vents to a big mouth and if there are no main on the end of the supply mains then cut on one in to vent out the mains this lets your traps do less venting . By some hardiness and ph strips and check your make up water it good to know.Peace and good luck clammy

RedChops

Well, the pipe rehanging didn't go completely to plan. I couldn't drop the pipe much at all throughout the run as it's bound by the radiators and takeoffs. I was able to lift the horizontal supply main to the first elbow enough to create a downward-towards-return slope through the supply. This exacerbates the counterflow that was already present in that area, but has almost totally eliminated the knocking and in terms of pitch will have to do till spring/summer when I can get a crew out to repipe the near-boiler piping. My guess is that there was counterflow or a sag near the takeoffs to the upper floors and the standing water was getting sucked up in to those mains. I still have two radiators that aren't heating, but progress is being made!

I've got a big mouth on order now, so I'll be interested to see how that helps with the venting. The vent that's on there now pretty audibly struggles with the amount of air that's trying to come out of it. I've got some additional insulation plans for the rest of the pipes as well.

For the skimming, I have access to a 2" port with a reducing (expansion?) coupler to 2.5" that's capped off. I don't think I'll be able to get that cap off, so I'm probably going to have to break off that coupler. My question here is: is 2" too large for a skim port, and I should reduce it to something like 1"? Space willing, I'm probably going to make it a permanent port with a capped tee for chemical, whatever I end up doing.

RedChops

Attached picture shows the port I’m thinking about using for skimming.