Water hammer and uneven heat

SteamStruggles

I recently had a steam boiler repiped and it was clearly a bad decision. I had multiple contractors convince me that the header coming off the boiler was too low and it would decrease the longevity of my boiler in the long term. I had one repipe the boiler but since doing the work, there has been a terrible water hammer at start up (in pipes throughout the house), short cycling of the boiler, and one of our radiators (we only have 5) gets almost no heat. The steam also sounds "wet" - like I can hear water in the pipes when the boiler kicks on - which we didn't have before.

These problems started with the repiping but the contractor insists their work on near-boiler piping is solid. My two leading hypotheses: 1) the Hartford loop's nipple at the top is too long (although I don't see why that would cause these problems) and 2) the main supply slopes slightly up when it turns from above the boiler. Any other thoughts?

I have included an image of the boiler BEFORE the work, the current state of the boiler (longer risers coming off the boiler), and the slope on the initial main supply coming off the boiler.

My wife and I have our 3rd kid arriving in a month and already aren't sleeping from the water hammer. Any hep is greatly appreciated!!!

KC_Jones

Did they skim the boiler after the repipe?

New piping will introduce oils which could cause surging and in part explain the issues.

I agree the header was too low, but unless you were already having problems I probably wouldn’t have touched it.

What issues were you having previously that they were trying to solve with the header change?

EzzyT

The near boiler piping is still wrong, it needs to be repiped.
The gas piping also need to be addressed.
Whose bright idea was to tape off the boiler draft hood and install a draft regulator? 

SteamStruggles

The boiler didn’t turn on this winter. So we replaced the electrical box and it turned on, but the contractor advised the piping was bad and we needed a chimney liner. We decided to rectify both issues, but now I’m of course regretting it. 

I assume they skimmed it, but will confirm.

The contractor who replied it closed the draft hood. I argued with them about it, but they claim it’s safer for CO - and I don’t feel well placed to argue with pros…

SteamStruggles

What issues do you see with the repiping?

STEAM DOCTOR

Can you take a few more pictures of the piping? Try to get around to the sides. Have you checked the water level? Make sure it's not too high in the glass. Does water jump up and down a lot when boiler is firing? And definitely check pitch of all the pipes. Water needs to be able to drain out. Whether it's the boiler piping or the piping higher up. Not so sure you need to skim, because does not look like any threading of pipe took place. Seems like everything is mega pressed. But watching the water while boiler is firing will give you an indication about necessity of skimming. 

SteamStruggles

Yes there is surging in the water level. And even clumps of rust that will come from the top of the viewing glass. The return pipes are of course hard to see but the supply main seems pitched up slightly (in the one picture I sent - pitched lower at the boiler end) or totally flat in the rest of the run as it goes to the radiators. 

SteamStruggles

Which maybe suggests more skimming is needed…

Neild5

If clumps of rust are in the sight glass with surging, it should be flushed and skimmed.  Also the Hartford loop is wrong, it should be a close couple, the longer it is the more water hammer.  See the blue circle.  Also the gas line should be hard pipe to the boiler.

neilc

is there a skim port there ? (picture?)

if you sit at the boiler, is the hammer more pronounced at the hartford loop connection? can you feel it there?
that nipple is long and could be your hammer,
fitter should have used a ell there,

Jamie Hall

Sorry, but i need to see pictures of the steam mains, including the connection(s) to the header and any drips -- with at least some indication of which way they pitch and how much. Both the uneven heat and the hammer may be due to condensate in the mains not being able to drain easily.

SteamStruggles

SteamStruggles

Lot of photos...
Photo 1) Supply is the lower pipe on the right, going to radiators in the front of the house
2) Maybe most concerning? Supply turning immediately at the top of the boiler (pitched such that the end leading from the boiler is lower - so steam goes against gravity)
3) Return from front of house
4) Return (lower) and supply (above) going to radiators in the back of the house
5) Main supply going out of the boiler closet
6) Riser off the boiler
7) Return into boiler closet (note it is now lower that before the repiping which I would think is a good thing - you can see the hole in the drywall has moved down)
8) Supply pipe coming off the boiler
9) Another angle of header/piping above boiler

Jamie Hall

This is a two pipe system? Are any of the dry returns hot? Not as hot as the mains, but hot? How is the system vented?

Now in terms of level... that long dry return from the front of the house (you can see the kitchen) seems to be dead level. It shouldn't be. I don't know where the drop to the wet return and boiler is, but it must be sloped -- not that much, but a half inch or more towards wherever it drops.

Everywhere else, do some thinking: if you were water in that pipe -- main or return doesn't matter -- how are you going to drain back to the boiler? And then, if you were air, how are you going to escape?

SteamStruggles

It is a two pipe system with a single vent on the dry return in the boiler closet. The return piping is very hot when the boiler is running.

So should the supply pipes also slow back from the boiler (so boiler is the lowest point)? The installation manual says supply should "slope down from high point above boiler and drip ends of mains into wet return".

Thank you for all the information!!

Jamie Hall

If the return piping is very hot you may have one or more steam traps on radiators which are failed open. The dry return can be warm -- but should never be so hot that you can't hold your hand on it comfortably. And all it takes is one failed trap...

So, check all of them. The outlet from the trap should be at least 5 degrees cooler than the inlet to the trap. Don't depend on absolute temperature readings, as the finish on the pipes may throw them off -- but if the finish is similar the relative readings will be OK. If you find a radiator with a trap which is the same or very nearly the same on the outlet as the inlet, that would be a good one to repair...

SteamStruggles

I don’t think my radiators have steam traps?

They all pretty much look like this:

Jamie Hall

The valve looks like it may have been from a vapour system. It may have a limited opening sized to the radiator. Alternatively, that harmless looking elbow on the outlet may have some hidden bits -- either way to keep steam from getting into the return.

Best to run that system at very low pressure -- less than 8 ounces cutoff.

Onepipe

You are correct that you do not have traps on you radiator, or at least that one. In the picture you have a Trane vapor system. Assuming that all your radiators are set up that way your system needs to run at very low pressure, 6oz or so or you will blow out your water seal and have steam in your dry returns like you are experiencing. I am guessing that your contractor did you a favor and turned up the pressure for you when they re piped the boiler. If you do not have a vapor stat you really should on that system. Steam in the dry returns (especially ones that do not have pitch) can cause alot of hammer. Also by chance did your contractor adjust any of the handles on the radiator valves when they were working? Those systems need to be adjusted for the size of the radiator. Roughly 80% of the radiator should ever see steam so that only condensate is getting to that return 90.

SteamStruggles

What is a water seal? It did sound like there was water pouring through the pipes when they first set it up (and then they realized the pressure was too high - 8 lbs, they said they had a miscommunication on the phone and thought it was ounces…). Sounds like the pressure is still too high (at 2 pounds) but what should I do about the water seal / what is it? Thank you!!

Onepipe

I would recommend buying a copy of Dan holohan’s “lost art of steam heating” as you can learn a lot from this text. There is information in chapter 15 of his text on the trane system and specifically the return elbow. The water seal is a small puddle of condensate that is located in the radiator on the exit side. So for your radiator in the picture you should have a 1” in 20’ pitch toward the supply and return side (some times the supply is on the opposite side of the supply and in that case you would pitch toward the return.) this puddle keeps steam from leaving through the lower hole of the 90 located at the bottom of the radiator. When the pressure gets too high the incoming steam will push the water out of the radiator and dry out the water seal leaving an open pathway for steam to enter the dry return. You need to fix this by lowering your pressure to 6oz or as low and you can and adjusting your radiator supply valve so that the rad only ever sees 80% steam ensuring condensate is the only thing that can reach the return 90. It sounds like your installers messed up the pitch in you pipes when they changed the header and heartford which is causing condensate to build up and get pushed around by the steam and cause hammer. I had the same issue with a different type of vapor system that the previous installers pushed the dry return pipes up 3” in the wrong pitch direction……but they saved on install time and fittings, so there is that…. There was a small lake that came out of the dry return when I re pitched it. I’m not sure if you have found a new contractor or now but at this point their free repair work may not be worth it. Find a reputable mechanic that knows what a vapor steam system is and you should be all set. 

SteamStruggles

Really helpful - Thank you.

If anyone knows a reputable mechanic who knows vapor systems in Washington, DC please let me know.

KC_Jones

@Dan Foley is the person you need to be contacting for sure.

https://heatinghelp.com/find-a-contractor/detail/foley-mechanical-inc