Hammer Issue - Incorrect Near-boiler piping?

nbny88

Hi there,

Total newbie here. Earlier this year, we purchased a 1910 American Foursquare home with two pipe steam heating. I’ve only owned homes before with forced air and baseboard heating. Needless to say, it’s been a learning curve. I’ve been reading many posts on this site about people dealing with water hammer, trying to understand what could be causing my issue. Here’s a breakdown of what I am experiencing:

- Loud water hammer/clanking sounds mid firing cycle. It doesn’t seem to hammer at the start of the boiler firing, and it seems to be worse when the pipes have been cold for some time
- Water hammer sounds seems to be concentrated at two back-to-back Baseray baseboard radiators (separate rooms, sharing the same wall). Both are level. When the hammer is bad, I can feel the radiators almost jump. One of the radiators heats immediately, while the other often takes much longer to heat, and often never heats up at all on a shorter fire.
- Water hammer not present in other parts of the system and radiators/pipes throughout the house
- Water in glass gauge is rust color, and during the firing cycle, jumps a bit and lowers to just an inch of water, before rising again after the boiler shuts off
- Whistling on a few of the radiator air vents, some of which have which have recently been replaced. One is even spewing a little water.
- All radiator valves are open, as far as I can tell

Additionally, I have a local friend who is also an experienced (and well-rated) plumber. He’s been consulting with me on the system, and has recently suggested that the near-boiler piping is wrong. I’ve attached some pictures for reference. He’s thinking that:

- Copper instead of steel was used above the water line (a big no)
- Piping is too small and has been downsized from proper size out of the boiler
- Basically, the steam is trying to rise against unlike pressure, causing the hammer

Finally, the hammer noise seems to be concentrated on the other side of the house, away from the boiler, and not from/around the near-boiler piping. Any thoughts based on my pictures? Any other wisdom would be greatly appreciated. Thanks for reading!

Ironman

Yep, the piping is configured wrong and is too small. The boiler needs to be skimmed.

The copper needs to be replaced with black iron.

What's the setting on the Pressuretrol?

nbny88

@Ironman - thanks for the reply, very helpful. PSI on the gauge never seems to move, even at firing. The pressuretrol is set near the top, which might be too high? I was under the impression this setting wasn't impacting the boiler pressure, rather creating a cut off if the pressure ever gets too high, which it doesn't seem to be.

Ironman

The gauge is worthless. The pressuretrol should be set to 2 psi or less.

The pigtail that the Pressuretrol is on may be plugged causing the control to have a false reading. Take the Pressuretrol off of it and clean out the pigtail (with the boiler off).

nbny88

I've lowered the PSI to 1.5. We'll see if that does anything to help in the meantime while we wait to re-pipe the near-boiler setup to steel in the spring.

Thanks Bob!

Jamie Hall

As has been noted... the near boiler piping, while neat, is a total catastrophe. I usually operate on the "if it ain't broke, don't fix it" rule -- but, even though it's likely that that bad boiler piping isn't really the cause of the hammering -- although it won't help -- it's bad enough that I would recommend that you fix it properly. Black iron, swing joints, proper sequencing, proper sizes. Both you and your boiler will be happier.

Presssuretrol is set way too high. But that's been mentioned.

Now... the hammering. Baseboard type radiation and one pipe steam do not play well together. However, it's not hopeless (only almost). As a first try, make very sure that the inlet valve is fully open. Then make sure that the baseboard has plenty of pitch towards the inlet end. Level won't do; they need to have at least a quarter inch of pitch per foot of length -- more if the look of it can stand it. See if that helps any. You might also want to take a look at the vents -- it might help to slow the venting down.

If those baseboards still hammer... you may need to put a return from the end opposite the feed. This would need a trap on it and come back to the riser or, preferably, drop into the main or return below. Then pitch the baseboard that way instead -- though it wouldn't need much pitch. Kind of drastic, but...

Ironman

You need to check that pigtail. Most likely, someone cranked the Pressuretrol up because the pigtail is clogged. It's routine maintenance to have to clean them.

nbny88

Thanks @Jamie Hall - you mention that baseboard and one pipe steam are usually no good. My system is two pipe steam - is that better, or does that change anything you mentioned?

pecmsg

Is that a Brass T on the right riser?

Jamie Hall

nbny88 said:

Thanks @Jamie Hall - you mention that baseboard and one pipe steam are usually no good. My system is two pipe steam - is that better, or does that change anything you mentioned?

Much better! Almost feasible. Just disregard my mutterings about pitch towards the inlet -- and make sure they have some pitch towards the outlet end. Also make sure that the traps are working properly.

I was misled by the comment you made about vents. I presume now that you meant the vents on the mains or returns? If so, most of the hissing/spitting what have you should go away when you get the pressure down.

nbny88

Jamie Hall said:

nbny88 said:

Thanks @Jamie Hall - you mention that baseboard and one pipe steam are usually no good. My system is two pipe steam - is that better, or does that change anything you mentioned?

Much better! Almost feasible. Just disregard my mutterings about pitch towards the inlet -- and make sure they have some pitch towards the outlet end. Also make sure that the traps are working properly.

I was misled by the comment you made about vents. I presume now that you meant the vents on the mains or returns? If so, most of the hissing/spitting what have you should go away when you get the pressure down.

The two baseboards both have air vents on them, although different kinds. From what I can tell, the plumber who installed them did not install any valves. Pictures below:

Ironman

Individual air vents on rad's indicate a one pipe system.

nbny88

I'm pretty sure it's a two pipe system. Here's a picture of my kitchen radiator, for a better look. Steam pipe, and the return. Unless I am totally confused?.

Are vents not typically used on two pipe systems? All of my baseboard and older cast iron radiators have vents throughout the house.

Jamie Hall

@nbny88 -- that sure looks like those baseboards are one pipe. Can you find out what's hiding under those covers at the inlet end (opposite the vent) and the outlet?

nicholas bonham-carter

Or they could indicate failed traps.
Can you take the cover off, so we can see the piping?
I can see the original header above the boiler, with an equalizer.
When you repipe, you can tie into that, as should have been done before.—NBC

Ironman

If there are no traps, it could be an old 2 pipe air vent system. They were done before traps were invented.

If you search the main site, there's an article about it.

If that is indeed the type of system that you have, the return pipe has to be at least on size smaller than the supply or have an orifice that restricts it. If not, the rad will hold water and not drain properly while the boiler's firing. If your plumber ran the same size S&R to the BB's, that may be the problem.

nbny88

As far as I can tell, there are no traps on this system.

KC_Jones

2 pipe air vent was typically had both connections at the bottom. His rads are connected at the top and bottom, in addition the vent shown is in the wrong location for either one pipe or 2 pipe air vent. For me this indicates someone added them when they shouldn't have been there.

This is possibly an orifice system, or had regulating valves that were changed out.

Obviously this system has been touched by people that have no clue what they are looking at.

Where are you located? We may know a steam person in your area that can help.

nbny88

@KC_Jones good insight. I'm in Newburgh, NY, in the Hudson Valley.

Fred

That vent on the Baseray mounted sideways won't work either. The vent needs to be mounted upright. If those baserays are two pipe it shouldn't even be on that system. If those Baserays are one pipe, the vent needs to be mounted on an elbow or replaced with an angle vent.

nbny88

@Ironman and @Jamie Hall - here are pictures of the two pipes leading into one of the baseboards:

JUGHNE

And just to confirm that a clueless person installed this: the sight glass valves are reversed.

Also that right tee looks to be a 2 x 1 1/2 or 1/4 x 2 DWV tee with minimal bury for soldering.

Jamie Hall

That kitchen radiator shouldn't have a vent. The fact that there is one on it -- and in the wrong place -- strongly suggests that the whole system has been seriously knuckleheaded at some point. I wonder what it was when it began?

And I wonder where and what the two pipes -- in and out -- on those baseboards connect.

Before I go further out on any limbs -- a bad habit of mine -- I'd surely like to see a pretty well detailed piping diagram...

nbny88

Potentially an old Tudor system? Here's a different radiator for comparison, with the old valve still in use.

Mike_Sheppard

https://heatinghelp.com/assets/documents/492.pdf

Snowmelt

just a thought , could some of these rads be water insteam of steam?

Jamie Hall

That valve sure looks like a Tudor... in which case, my friend, you have some work to do.

Those systems depended on very low pressure to function properly -- no more than 6 ounces. As sort of a WAG, I'd say that someone messed up the pressure. Then things didn't work so they went and put vents on the radiators, making it into a **** form to two pipe air vent system.

My opinion is that you will be best served to fix the boiler piping, restore the main venting on the dry returns, put traps on the radiators which no longer have their Tudor valves, take all the other venting off, get the pressure down with a vapourstat, and work from there.

nbny88

@Jamie Hall I think you might be right on the messed up Tudor system. Though the air vent hole looks like it's a natural part of the radiator, which I believe were original to the house.

Separately, I just discovered these uninsulated supply and return pipes, and it's where the hammer noise happens mid-cycle. It's quite possible the steam is hitting those uninsulated pipes, and because of that open-air hole in the side of the house (that we'll be closing soon and putting in a proper vent) with cold air pouring through, the steam is turning to condensate and creating the hammer. It may also be why the Baserays, which are fed by these uninsulated lines, aren't heating up as fast as they should.

JohnNY

Thank you for reaching out, @nbny88. I hope to see you next week.
There are lots of things to remedy here and we'll go through them point by point to get you fixed up.

nicholas bonham-carter

I see the radiator vents are in the wrong place. The upper tappings are for hot water system use, and the lower for steam.—NBC