New Steam Radiator Causing Water Hammer

NewJerseyHeatHelp

I recently had a new radiator installed in a one pipe system. When the boiler kicks on, the water hammer starts a few minutes into the cycle. The radiator air vent and main line vent spit a good amount of water.

The radiator I had replaced was cracked and the supply valve was closed for at least 4 years, would it be possible because the valve was closed for so long it is causing this issue?

If I drain the boiler and then run the heat, the water hammer disappears, but will return in the after about three heating cycles.

The rest of the radiators in the house heat up fine and so does the new radiator, which is pitched plenty. The supply valve is fully open but it sounds like the water is having issues trying to leave the new radiator. When I close the supply valve to the new radiator, the water hammer does not happen.

Any suggestions or advice will be greatly appreciated.

Waher

What air vent do you have on the radiator? If it is venting too quickly for the size it could be filling with condensate from prematurely collapsing steam. Usually only happens with fast vents like varivalves.

NewJerseyHeatHelp

Yes, I even checked it with a level, it’s definitely pitched correctly. Possibly could try to get a few more shims under. The plumber originally had a varivalve adjustable vent but I went to Home Depot as I wanted to change it asap and picked up their standard angle #4. 

EBEBRATT-Ed

What do you mean by "If I drain the boiler the water hammer disappears but returns after a few cycles"???

How is the water level in the boiler? Is it surging or bouncing more than 1"?

NewJerseyHeatHelp

EBEBRATT-Ed said:

What do you mean by "If I drain the boiler the water hammer disappears but returns after a few cycles"??? How is the water level in the boiler? Is it surging or bouncing more than 1"?

If I flush the boiler water into a bucket then the autofiller fills the boiler, assuming this gets the air out of the system, the water hammer doesn’t happen but usually comes back in a few hours (cycles: morning, evening, and then it come back in the morning). I’ve closed the shutoff valve to the new radiator since I can’t always be home if the vents spit. 

The water level is fine, not surging 

Waher

Was a new supply valve and spud installed with the new radiator? If the old valve was reused with a new spud that could be the problem. Can you take a picture of the valve? If it was replaced it may be that a hot water supply valve was installed instead of steam and the valve body isn’t wide enough to allow condensate to drain beneath incoming steam. Could also be too small of a supply valve and spud into the radiator causing the same condensate traffic jamb.

NewJerseyHeatHelp

New spud and valve

Grallert

You have a pipe somewhere that is pitched incorrectly, and holding water. That's what's causing the hammer. That incorrectly pitched pipe could be why the valve was close in the first place, to stop the hammer. What floor is this radiator on?

NewJerseyHeatHelp

Grallert said:

You have a pipe somewhere that is pitched incorrectly, and holding water. That's what's causing the hammer. That incorrectly pitched pipe could be why the valve was close in the first place, to stop the hammer. What floor is this radiator on?

All the radiators are located on the first floor. 5 radiators in total. The pipe that goes into this radiator is partially hidden by a wall so I don’t have access to it. There is only one other radiator line that connects to the main on that side of the house so it has so be one of those pipes? I’ve attached the best picture I have on my phone right now. I know it won’t help much

NewJerseyHeatHelp

Grallert said:

You have a pipe somewhere that is pitched incorrectly, and holding water. That's what's causing the hammer. That incorrectly pitched pipe could be why the valve was close in the first place, to stop the hammer. What floor is this radiator on?

The old radiator has a crack in the air vent, assuming the old owner did this when either removing an air vent or installing.

Is there anyway I can fix the pitched pipe myself?

dabrakeman

Assuming the takeoff to the radiator is counterflow then raising the entire radiator (while maintaining proper pitch) is your easiest means of impacting the pitch in a positive manner.

NewJerseyHeatHelp

dabrakeman said:

Assuming the takeoff to the radiator is counterflow then raising the entire radiator (while maintaining proper pitch) is your easiest means of impacting the pitch in a positive manner.

Any chance you could explain in layman’s terms?

Waher

The pipe up through the floor into the shut off valve either was pulled up or sagged down creating a ponding of water in the main. You’re going to have to keep the radiator pitched to drain to the valve while trying to raise or lower the entire radiator with along with the valve to adjust the height of the main below to have the proper pitch. Or find the sag in the main and put a clevis hanger on it to pull the pipe up to the correct pitch.

NewJerseyHeatHelp

Here are some pics of the line that run to new radiator. Does anything stand out?

BobC

Make sure all the pipes on the basement have the right pitch first, the new work might have shifted the piping.
The fact your problem comes back a while after draining the boiler tells me you may have oil in tour boiler water and that means it needs to be skimmed. The new work probably introduced oil into the system.
It's free to try if your boiler has a skim port installed.

Bob

NewJerseyHeatHelp

BobC said:

Make sure all the pipes on the basement have the right pitch first, the new work might have shifted the piping. The fact your problem comes back a while after draining the boiler tells me you may have oil in tour boiler water and that means it needs to be skimmed. The new work probably introduced oil into the system. It's free to try if your boiler has a skim port installed. Bob

Thanks Bob, I’ve closed the supply valve to this new radiator and no more water hammer. If there was oil wouldn’t the issue still occur within the other radiators?

KC_Jones

That appears to be a counteflow main. Is that main vent the end of all the piping? If so it's definitely a counerflow and I'd be inclined to verify the pitch of the main to make sure that isn't the issue here.

If it is a counterflow, that vent location should be the highest point on that entire pipe run all the way back to the boiler.

NewJerseyHeatHelp

KC_Jones said:

That appears to be a counteflow main. Is that main vent the end of all the piping? If so it's definitely a counerflow and I'd be inclined to verify the pitch of the main to make sure that isn't the issue here. If it is a counterflow, that vent location should be the highest point on that entire pipe run all the way back to the boiler.

Yes that is the main vent and it’s counter flow. I can try to raise that pipe end

BobC

If you close the valve steam will not enter that radiator or much of the pipe that feeds it. If the slope is not very good on the piping that deeds that radiator it would be more likely to hammer.

If you try skimming and it helps your going the right direction, if it doesn't work you have crossed a possibility off the list and cost yourself nothing.

Bob

NewJerseyHeatHelp

BobC said:

If you close the valve steam will not enter that radiator or much of the pipe that feeds it. If the slope is not very good on the piping that deeds that radiator it would be more likely to hammer. If you try skimming and it helps your going the right direction, if it doesn't work you have crossed a possibility off the list and cost yourself nothing. Bob

I open the new radiator yesterday morning after the heat had already started and it worked all day yesterday perfectly fine, no water hammer. This morning the water hammer returned about 15 minutes after the heat turned on after being off for about 8 hours. Could this do with the lines being cold? Would insulating the lines help at all?  

STEAM DOCTOR

We have skipped the most important step. I think. You need to check the pitch of every single pipe leading to that radiator. 

NewJerseyHeatHelp

STEAM DOCTOR said:

We have skipped the most important step. I think. You need to check the pitch of every single pipe leading to that radiator. 

I’ve checked the pitch of the all the pipes, I believe that they are all correct. 

Jamie Hall

NewJerseyHeatHelp said:

BobC said:

If you close the valve steam will not enter that radiator or much of the pipe that feeds it. If the slope is not very good on the piping that deeds that radiator it would be more likely to hammer.

If you try skimming and it helps your going the right direction, if it doesn't work you have crossed a possibility off the list and cost yourself nothing.

Bob

I open the new radiator yesterday morning after the heat had already started and it worked all day yesterday perfectly fine, no water hammer. This morning the water hammer returned about 15 minutes after the heat turned on after being off for about 8 hours. Could this do with the lines being cold? Would insulating the lines help at all?  

What was off for 8 hours? The heating system as a whole, or did you turn that one radiator off with the inlet valve?

NewJerseyHeatHelp

Jamie Hall said:

BobC said:

If you close the valve steam will not enter that radiator or much of the pipe that feeds it. If the slope is not very good on the piping that deeds that radiator it would be more likely to hammer. If you try skimming and it helps your going the right direction, if it doesn't work you have crossed a possibility off the list and cost yourself nothing. Bob

I open the new radiator yesterday morning after the heat had already started and it worked all day yesterday perfectly fine, no water hammer. This morning the water hammer returned about 15 minutes after the heat turned on after being off for about 8 hours. Could this do with the lines being cold? Would insulating the lines help at all?  

What was off for 8 hours? The heating system as a whole, or did you turn that one radiator off with the inlet valve?

By heat being off I meant set to 62 degrees for overnight (from about 10 pm to 6 am). At 6 am when the thermostat schedule turns to 68, I started hearing banging around 6:15 am in the supply line that runs from the main to the new radiator. Turned the system off, closed the inlet valve to the new radiator and haven’t had the water hammer since and other radiators have been working just fine. 

My gut feeling says it has to do something with the supply line. It seems to be pitched correct, I can only access about 3 out of the 10 feet of it since the majority of the pipe runs behind a wall. 

This supply line is probably double the length of any of the other lines that run to the other radiators, not sure if that means I have to do anything differently to the new radiator (different vent (slower/faster?), more/less pitch?)

Jamie Hall

It may be that the supply line is either too small for the size of the radiator, or has inadequate pitch. How big (EDR) is this radiator?

NewJerseyHeatHelp

Jamie Hall said:

It may be that the supply line is either too small for the size of the radiator, or has inadequate pitch. How big (EDR) is this radiator?

Not too sure how to calculate it but it’s 27 inches long (16 sections), 26 inches tall and 4.5 inches (4 tubes) wide. 

delcrossv

Why is the vent in the hot water bleed valve location?

NewJerseyHeatHelp

delcrossv said:

Why is the vent in the hot water bleed valve location?

No clue, I did not put it there, the plumber who installed it did 

clammy

Other have said vent in wrong location . If a plumber did this then he does not know much about steam systems being he installed the vent in the wrong location . There should be an Allen key screw about 2/3 of the way up . Remove the vent and re locate and install the Allen set screw where your vent is currently . The banging issue your having may have to do w one of two things the set back on the thermostat and possibly the supply pipe size to the edr of the radiator . If the radiator is over sized for the riser then you could be under feeding the rad which will cause more condensate to form then the radiator will drain . If this is a replacement radiator was it sized larger then the original one which was there ? What size vent is one the radiator possibly over venting the radiator . I also see there s no insulation on your steam piping for a counter flow system dry steam is extremely important and if your boiler is poorly piped and uninsulated steam mains well it does not help things . Possible see if you can raise the whole radiator and also pitch it back to the supply valve . Start off by putting that vent in the correct place . Vents installed on the top side of a radiator does not speed the heating only lets about 1/2 the rad get hot before the vent closes .
Peace and good luck clammy

NewJerseyHeatHelp

clammy said:

Other have said vent in wrong location . If a plumber did this then he does not know much about steam systems being he installed the vent in the wrong location . There should be an Allen key screw about 2/3 of the way up . Remove the vent and re locate and install the Allen set screw where your vent is currently . The banging issue your having may have to do w one of two things the set back on the thermostat and possibly the supply pipe size to the edr of the radiator . If the radiator is over sized for the riser then you could be under feeding the rad which will cause more condensate to form then the radiator will drain . If this is a replacement radiator was it sized larger then the original one which was there ? What size vent is one the radiator possibly over venting the radiator . I also see there s no insulation on your steam piping for a counter flow system dry steam is extremely important and if your boiler is poorly piped and uninsulated steam mains well it does not help things . Possible see if you can raise the whole radiator and also pitch it back to the supply valve . Start off by putting that vent in the correct place . Vents installed on the top side of a radiator does not speed the heating only lets about 1/2 the rad get hot before the vent closes .
Peace and good luck clammy

I've seem to strip the lower allen key head this morning before work (i should have waited until i was fully awake), after I get it out, would I be able to use a 1/8 in. MIP Plug Fitting in the higher vent since i wont be able to relocate it?

The new radiator is about 6 inches taller than the previous one but the same length and width.

The issues only seem to happen on a "cold" start, when the boiler starts up in the morning at 6 am after being off from about 10 am? Could it be since the supply lines are warming so quickly and the pipes being cold its producing extra condensate? i'm assume insulating could help with that? When the supply valve is closed at this radiator, the system works perfectly normal.

delcrossv

"I've seem to strip the lower allen key head this morning before work (i should have waited until i was fully awake), after I get it out, would I be able to use a 1/8 in. MIP Plug Fitting in the higher vent since i wont be able to relocate it?"

Correct.

"The issues only seem to happen on a "cold" start, when the boiler starts up in the morning at 6 am after being off from about 10 am? Could it be since the supply lines are warming so quickly and the pipes being cold its producing extra condensate? i'm assume insulating could help with that? When the supply valve is closed at this radiator, the system works perfectly normal."

Insulation and correct pitch. Cold start leads one to think there's not sufficient pitch to get the condensate out of the pipe.

clammy

Looking at your radiator picture I’ll suggest instead of all the shims stacked how about this .
First disconnect the radiator from the supply valve and slide the radiator over alittle . See if the supply valve can be lifted up if so figure out about how height it can go to keep the valve lifted .Instead of stacking shims go get a piece of wood say a 2 x4 cut a few inches wider then your radiator and use that to get the radiator at the correct height maintaining and possibly increasing the pitch on that supply line . Aside from the air vent in the wrong location I would think the hammering really has to due w the difference in the replacement radiator height to the original rad.
Peace and good luck clammy

Sylvain

If steam condensate too rapidly in the riser, what about venting that radiator more slowly?

NewJerseyHeatHelp

Sylvain said:

If steam condensate too rapidly in the riser, what about venting that radiator more slowly?

I just got a vent-rite #1 that has the adjustable dial, plan to put that on and test the system over the weekend when I’m there to monitor it all day

Jamie Hall

Back to basics. Water hammer in a steam system can only occur where sufficient water can build up in a near horizontal pipe to be pushed into a wave shape by the steam or air going by, and then that wave can be propelled along the pipe to where it hits a bend (either horizontal or vertical) and stops. Bang.

So the three necessary ingredients are enough condensate, enough velocity, and a stretch where the condensate can pool enough to form into a wave.

So... is the pipe big enough to handle the steam flow at a reasonable velocity? That's why runouts are sized based on the EDR they feed. Is the pipe slope constant -- no flatter stretches, never mind sags -- and adequate to allow the condensate to flow in a very shallow stream?

ethicalpaul

Back to basics. Water hammer in a steam system can only occur where sufficient water can build up in a near horizontal pipe to be pushed into a wave shape by the steam or air going by, and then that wave can be propelled along the pipe to where it hits a bend (either horizontal or vertical) and stops. Bang.

It's not the sudden collapse of steam coming into contact with cool water causing a vacuum that then causes an inrush of air that propels the water? I don't think the velocity of normal flowing steam from a boiler would cause water to slam into a pipe to cause a bang but I've been wrong before.

Jamie Hall

Honestly the mathematics is more than I want to mess with at the moment. However... let's consider a conservative velocity for steam (or air) moving in a pipe. 20 feet per second. That's about 12 miles per hour -- a stiff breeze. Have you ever observed the waves on a pond at that wind speed? They can build up to a pretty good sized ripple. Put that ripple in a pipe, and it can block a good fraction of the pipe -- and be pushed along by our friendly breeze. That's what's happening.

But... but.. even a well vented system doesn't heat 20 feet of main or runout that fast? No, it doesn't, and the reason is that the advancing steam front has to heat the pipe first, and that takes time (and builds up condensate which, we hope, can drain away...). So eventually the pipe is hot, the steam is whipping along, and -- if the condensate didn't drain away in time, we get waves. If we are lucky, we get one. If we are less lucky, we get successive waves until all the condensate has managed to drain away and the banging stops. If we are really less lucky and have a counterflow situation, that doesn't happen -- and the banging just keeps right on going until the boiler shuts off.

ethicalpaul

Thanks Jamie I'm with you on all of what you wrote except how a breeze can slam water into a pipe that sounds like a hammer hitting it.

that's why I'm in the "steam collapse vacuum" camp

dko

I think you're both correct.. as there is more than one way to create water hammer. One is just more powerful than the other.