Water Hammer at Radiator

alaw · November 12

Hi All,

We had a new boiler installed summer of '22, a Peerless Series 3 natural gas boiler for a one-pipe system. We've had issues with water hammer in the past but it has become more consistent and stronger with the change. It mainly occurs at the radiator with one radiator, nearest to the boiler, as the nastiest offender. The radiators are level, or slightly pitched to supply side.

Symptoms:

Only happens on first floor.
The worst radiator is on an outside, uninsulated wall but the other offending radiator is on an inside wall.
More hammer when cooling vs heating. Some pings when heating but much worse when cooling. Violent.
More hammer when very cold outside.
Minimal hammering when I drain the boiler from the bottom port. Water is dirty at first then runs clean. After a couple heating cycles, the water hammer comes back in full force.
There is no spitting, the radiators heat nicely and at about the same time. There are no issues with the radiator on the second floor or in the kitchen. 5 radiators in total, the 3 larger ones are the ones effected most.

Diagnosis?:

Needs to be skimmed? What I think is the skim port is plugged. Not sure how to install a drain for that, nothing I could find on youtube.
System not balanced and I need to add more air vents on the mains? I'm not really sure what I'm talking about here so I'll post pictures of the piping. There is only one vent in the basement and its on the header.
Pitch the radiator more? That doesn't seem like the answer.
Change the air vents on the radiator, slow them down?

I've done some research but I'm lost. I appreciate any help, there are a ton of factors to consider and a lot of knowledge required to diagnosis, which I do not possess.

Thank you

ethicalpaul · November 12

The boiler is piped wrong, that could definitely be involved
The water level in your picture is low…does it go low like this when you're making steam and then return after the call for heat ends? If so, you are surging. That's an indication you need to skim the boiler.
I see a lot of gunk in your gauge glass. That's another indication you need to skim the boiler.

You can look in the Peerless 63 (not Series 3) manual to see where the skim port is. It's here, it looks like your installer (who didn't look in the manual or he would have seen how to install the piping) might have blocked it with his piping. Sorry but your installer doesn't know what he's doing at all.

Jamie Hall · November 12

Well, to start with the near boiler piping is just plain wrong. I several ways. I suspect you are getting a good deal of carryover water into the mains — and the first place that will show up is (bang, clang) the nearest radiator. The main vent — seen in the fifth picture — is too small and to close to the boiler — essentially useless.

For starters.

As to noise, however, it's important to clearly distinguish between water hammer and expansion noises — and it is likely that if you are hearing pings or even bangs when the system is cooling, that that is expansion noise. You need to look at where pipes are or could be in contact with wood, or rubbing on things.

ethicalpaul · November 12

The main vent — seen in the fifth picture — is too small and to close to the boiler — essentially useless.

I agree it's too small, but isn't it at the end of the main? That location seems OK.

KC_Jones · November 12

https://forum.heatinghelp.com/discussion/comment/1819663#Comment_1819663

I have one of my mains vented in that location and it's fine. I agree that it's too small.

alaw · November 12

@KC_Jones @ethicalpaul @Jamie Hall

Thank you guys. Although this is a bit disheartening as the person who installed the boiler is the only plumber who does with steam heat in southern Maine.

First things first, I need to sort this near boiler piping. I've played the "Spot the Difference" game with the manual and the boiler. The main difference I see is that there is no "reducing elbow" and the steam supply header (not sure of nomenclature) should be before the reducing elbow.

There is also no nipple/cap at number 14/16 in diagram below.

In my photo, I've added some markups for clarification. I think yellow= smaller diameter condensate return and red = mains?

Do I have this straight? The yellow pipe connects into the main at the far end of the basement, acting as a return for the radiators furthest from the boiler. The condensate from the closest radiators to the boiler returns via the main (red).

I'm trying to understand how the way it is currently piped is causing problems. Is it basically that water is coming up the from the boiler through the equalizer into the main (red pipe)? And am I correct in thinking that the reducing elbow would prevent this from happening?

Also, the vent on the yellow pipe is the only vent in the basement. If my understanding is correct than this is totally pointless, steam is not hitting that vent to close it. The yellow pipe is only connected to the header via the main at the far side of the basement (in the marked up photo, it's where the red and yellow nearly touch). Shouldn't the main vent be on a larger red pipe that branches off to the radiators?

Man I learned a lot about steam heat today.

Thank you again

Jamie Hall · November 12

The problem in the near boiler piping is that the riser comes up, then the header goes over into the leg of a T and the steam is supposed to go up and the condensate/carry over down. It won't. The steam going up is going to carry it up and into the steam mains. Clank.

Have to go — more later.

ethicalpaul · November 12

It can be hard to see the difference when you haven't looked at a lot of them, but basically the way your pipe goes straight up from the boiler to the main is not right.

You want to make the output of the boiler go to the horizontal header, THEN you have vertical supply pipe(s) coming off the top of the header, THEN the header continues over to the side where the equalizer can drain any water back down to the boiler.

This header design helps to separate water from the steam.

If everything is perfect, the steam will come up from the boiler already dry, without water droplets, and a header isn't necessary, but you don't want to pipe a boiler for perfect steam production, you want to pipe it for a range of situations.

dabrakeman · November 12

"Do I have this straight? The yellow pipe connects into the main at the far end of the basement, acting as a return for the radiators furthest from the boiler. The condensate from the closest radiators to the boiler returns via the main (red)."

More than likely the highest point on your main is above the boiler and it pitches downward to the far wall where it then reduces size and comes back to the boiler continuing its downward pitch. If so you have parallel flow system which means the steam and condensate travel in the same direction away from the boiler in the mains. Given your main vent location steam will also travel through that smaller diameter main extension all the way back to your main vent until that main vent closes. All condensate from the radiators will flow back to the main via the same path the steam entered through the takeoffs from the main then it will run downhill to the end of the main and back to the boiler through the smaller diameter main extension.

To verify you can sight your main relative to the floor joists as a sanity check on the pitch if you can't get a reading with a level.

alaw · November 13

@ethicalpaul @Jamie Hall So what is happening is steam and water are being carried out of the boiler. If designed properly, the steam would shoot vertically through riser into the mains as water is propelled horizontally and back down into the boiler. Makes sense.

Is this a relatively easy fix? Could any plumber do it. I'm considering if I should try to salvage this relationship with the installer because there is no one else who services steam boilers here in my part of Maine. We only use him for the boiler.

@ethicalpaul the water in the sight glass was low and gunky. It was low because I had just drained the boiler a bit to rid gunk out the bottom. Normally the water level is stable during operation however the gunk would indicate something else. I will have to pay attention next time it fires up. Either way it seems like it needs to be skimmed and that the installer omitted this during install. The manual does say to install a 1-1/4" ball valve and drain into that port.

@Jamie Hall The noises do happen when the system is cooling. Is this absolutely not a piping/dirty water problem? The banging feels like it happens close to the radiator but our house is small so I may be misjudging the origin of the bang. If it is expansion, it didn't happen this often before the boiler was replaced and none of the "far-boiler" piping was changed. Any ideas?

You all have been so helpful. Now I have to decide how to fix.

ethicalpaul · November 13

it's not really salvageable to change it. He used expensive press fittings that can't be reused (to my understanding).

There is a chance that if the water quality can be sorted out through skimming that the boiler could make good steam without surging, it's definitely worth a shot.

This gauge should be at the bottom:

The "Hartford Loop" should be a couple inches below the water line. It sounds like you might have had the water line low during this photo, but if this short horizontal pipe is at the water line, it can result in banging.

Also, that short horizontal part above is supposed to be even shorter to prevent banging.

alaw · November 15

@ethicalpaul thank you. This has been extremely helpful.

The gauge you indicated is the limit control, correct? It seems to be install properly according to manual, right?

Screen Shot 2024-11-14 at 6.24.05 PM.png

I'm hoping we can get a skim port installed.

As for cooling down bangs, it's kind of a "tink-BOOOM". I've looked up some videos of expansion noises and it doesn't sound similar to mine.

I'm going to replace the main vent with something larger. From what I've read, a parallel flow system cannot be vented fast enough. Current vent is no.35 VENT RITE 3/4"x1/2", could I simply replace with Barnes&Jones big mouth? The big mouth is 3/4" npt, will that just thread into the pipe?

ethicalpaul · November 15

Well, all the controls come installed from the factory so yes they should be correctly installed.

You can vent any system fast enough.

I don't like the Big Mouth very much, if I recall correctly it has a female 3/4" thread. I like the Gorton #2 better. It has a male 1/2" thread. (the threads have nothing to do with my likes or dislikes, I just state them because you asked)

alaw · November 15

@ethicalpaul thank you. I came to the conclusion that you can't vent fast enough based on a PDF I found on this site. It said take off the main vent, run the system and time how long it takes to get steam leaving at the opening. That is how long you want it to take with a vent, therefore vent as fast as possible.

Ordered the Groton no.2 and will keep tinkering with the system.

ethicalpaul · November 15

Yes, by performing that timing you will see that you can easily have enough venting so that the time to fill the main with steam in about the same as how long it takes with an open pipe. And to my mind, that is fast enough.

Therefore, you can vent a main fast enough.

This thinking that "no venting is too much" is just costing people a lot of money and effort for no benefit. I don't like it. Also, for each vent you add to an antler, you are increasing your odds of a steam leak occurring.

Jamie Hall · November 15

Agreed. From the standpoint of wasting time and a good deal of money, there is a definite point where venting a main is enough — and more isn't going to help anything. The rather simplistic "you can't over vent a main" is valid enough in that it won't hurt anything — but misses the point that it won't help, either!

For reference, the system Cedric powers has about 200 feet total of 2 1/2 inch and 3 inch mains, plus all the radiators, venting into the dry returns, which go back to the boiler, and the whole thing is vented with one Gorton #2 and a Hoffman #75. Works fine.

Water Hammer at Radiator

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