Water Hammer, Loud Radiators and Pressure Cycling

adrian123

Hi all,

Big thanks to all the contributors on here as all the posts have been so helpful in trying to work out the issues with my one pipe steam system.

When we first started using the heat we had some water hammer, particularly in the two rads furthest from the boiler but after insulating all the pipes, lowering the pressure, checking the pitch and raising the rads as needed, it more or less stopped. But since the cold weather really kicked in this past week in the NYC area, we've had really bad hammering, so strong that you can feel the reverberations in the floors. And it sounds like the water moving in waves or surging in the rads. Also the noise level of each radiator vent has increased considerably. I replaced every old vent in the house with Hoffman 41s and now they are whining/whistling very loudly.

I replaced the main vent, an old Dole that didn't close, with two Gorton #2s but after doing more homework I am thinking that I need to add vents in other places on the main. I just put the two new ones in the spot where the old one was. The basement piping goes in a rectangle with the risers moving off them in 6 places. The pipes are pitched to drop from the front of the house to the back and then make two turns to head back to the boiler. The vents are at the spot where the pipe drops first before it meets the drip connection. In the last picture they are right above where the washer/dryer are. I also replaced the pigtail and added a 1-5 PSI gauge. After re-calibrating the pressuretrol the cut out is about .8 PSI. But the boiler cycles multiple times before the stat is satisfied.

My assumption is that the mains aren't venting well, leading to too much air at the rads, thus the noise and the short cycling. The position of the vents seems wrong as the steam looks like it would hit all the risers before even getting to them? And could the increased water hammer be because of the lower overall temperatures which means colder pipes and thus the steam condensing faster and not being able to get back to the boiler?

Any advice would be greatly appreciated! And BTW the riser off the boiler is copper and at one of the joints you can hear steam hissing so that might be a whole other issue.

Jamie Hall

You have some real problems with the boiler piping -- but it's late. I'll get back tomorrow morning, but in the meantime others may have more comments.

neilc

that picture of the boiler, is, different,
post a shot of the other side showing all that pipe above like you did on this one,
No equalizer ?
looks like a wet steam percolator from here.

JUGHNE

Just one main running around the basement?
Can you show us how it returns to the boiler?

adrian123

It's hard to get a great shot of the other side of the boiler because the water heater is right next to it but here goes. Just one main running in a rectangle around the basement. The vents are just over my left shoulder in the first shot. And I probably didn't need to insulate the wet returns but oh well.

And I agree on the near boiler piping, not looking great. It's a seven section boiler and the installation manual says one riser is ok for that so that's what they did.

KC_Jones

The boiler doesn't have an equalizer, so no way for any carry over to get back to the bottom of the boiler. Any water being sucked up out of the boiler from steam production is going out into the system. I would suggest this is part of the banging problem. Either you still have some sags holding the water, or the sheer volume of water being put into the system is overwhelming it's ability to deal with it, or a combination of both.

Jamie Hall

I thought if I slept on it... the basic problem is as @KC_Jones says: no equalizer, no header,

JUGHNE

Did this used to work OK, have you lived there previously?

Your return is close to the water level line, maybe wet--maybe dry.
Possibly the return line is sluggish and backing up water into the mains, that causes the hammer.

adrian123

Thanks everyone. This is our first winter in the house so I'm not sure how it was in the past. Before this cold spell I got rid of the water hammer after raising a bunch of the rads and increasing the pitch. But the really loud venting, "wave" sound of water moving in the rads and the cycling on pressure has been there from the start.

In the spring/summer, would it be worth trying to flush the return? And we had thoughts of replacing the boiler so that would be the time to address the near boiler piping I guess. How much of a job would it be to try to update with the existing boiler?

mattmia2

Given the age of that boiler, replacement would probably be the best option if you are going to put the labor and materials in to correcting the near boiler piping.

adrian123

understood, the thing I’m not clear on is why the water hammer is so severe now and in pipes I’ve not had it in before. Tonight you could see the pipe shaking and the noise was pretty serious. The sound of water surging in the pipes was also really noticeable. This is a new thing in the past week or so. 

nicholas bonham-carter

Is the pressuretrol the old mercury switch type, and is it out of level?
Lack of an equalizer will make it difficult to keep excess water out of the mains, causing the pulsating and hammering.
The return piping looks different as well.—NBC

Jamie Hall

adrian123 said:

understood, the thing I’m not clear on is why the water hammer is so severe now and in pipes I’ve not had it in before. Tonight you could see the pipe shaking and the noise was pretty serious. The sound of water surging in the pipes was also really noticeable. This is a new thing in the past week or so. 

Anytime I see a comment like this, the very first question I ask is: what changed? If things were good, and then something changed and things became bad, that's the very first thing to look at -- but you have to be a little careful about that. For one thing, you have to consider everything, not just what was intended or what the project was. Second, you have to consider -- did this change expose a pre-existing problem, and if so, what might it be?

adrian123

Thanks, @Jamie Hall . I did some thinking and observing and noticed this morning the water feeder was adding water when the line dropped towards the bottom of the sight glass during a cycle sight glass. And then when static the glass was all the way full. A few weeks ago I replaced a radiator that was leaking 1-2 bowls of water per day, so seems like the feeder was continuously adding water even when not needed. I took a few quarts of water out this morning and brought the water line down to the middle of the glass and the severe hammer has stopped. There's still a lot of noise at the rads and there's the larger issue with the near boiler piping but I can't do much about the piping right now.

Jamie Hall

Does your water feeder have a time delay on it? Some do -- set by dip switches in the feeder. Make sure that it has an adequate time delay to allow condensate to come back, and make sure, also, that it is set to feed a fixed amount, rather than just putting in water until the LWCO says to stop.

adrian123

There’s no setting for time delay or amount, it just kicks in when it senses the water level dropping, like after I remove some water using the blow down. So I have the feeder water shut off for now, and will just do add manually as needed.

JUGHNE

So during operation you have low water conditions and then after the cycle the boiler is over filled???

This could point to slow condensate return caused by sludge in the piping.

Has one thing, that has changed, is the outside temp...requiring longer run cycles?

adrian123

That seemed to be happening, from what I could tell, feeder was adding water as the boiler level dropped due to steam being created. The hammer is greatly reduced since this morning once I lowered the water level.

It doesn't really run on long cycles since I'm trying to keep the pressure low. From a combo of maybe oversized boiler (180k BTUs) plus poor main venting the pressure builds fast, so with having the cut out around 1-1.25 PSI the boiler short cycles. Letting it run longer would mean 2 or 3 or 4 PSI and then I have bad water hammer again.

I don't have it in me right now to try to tap the mains to add vents so I got a few Gorton Cs and Ds to put on the upstairs rads to see if that will help vent faster and keep down the pressure.

mattmia2

Was there oil in the new radiator or its piping that needs o be skimmed off the boiler? Oil in the boiler will cause it to surge and throw more water up in to the piping. How stable is the water line when it is steaming, is it mostly steady or does it bounce up and down a lot?

adrian123

The water line bounces quite a bit yeah, more than an inch of fluctuation. But that was happening before I put in the new radiator. One of the things on my long list of to dos is to skim the boiler. Need to read up on how to do it or watch some videos.

mattmia2

That is a huge part of your problem, that surging is going to throw lots of water up in to the piping. You may need to add a skim port, i'm not sure I see anything appropriate.

Jamie Hall

Keep the pressure down and put up with the cycling on pressure. That's costing you a lot less than letting the pressure rise -- never mind that it's helping with the hammering!