Main vent on dry return of a two-pipe radiator spitting water

bUBeHAdJoicKEt · April 2019

I have two-pipe steam baseboard radiators. One of the radiators has a vent on the dry return in the basement. This vent is spitting water like a sprinkler (and making loud noises during the process). Any help to figure out the cause and a fix will be greatly appreciated.

I originally had two VentRite #35 on the dry return. My heating company came and replaced that with VentRite #33 (for reason that is still not clear to me). But the effect is the same.

Some observations below, hopefully these will help.

I have two such radiators, but they seem to be behaving differently. Radiator1 does not have a vent on its dry return. Radiator2 does have the VentRite vent. Please see the attached pictures. In the picture that shows the vents, the vent in the center is the one spitting out water. The pipe left to the middle pipe (with vent) is the dry return of Radiator1. On the right side there is a Gorton #2 on returns from other rooms, and I have no issues with Gorton #2. Finally, these 3 pipes are connected at the wet return level as show in the second picture.

When Radiator2 (one with the vent on dry return) heats up, I have noticed that its return pipe heats up immediately. Whereas, in case of Radiator1 this is not the case. Radiator2 condensate pipe gets hot and as the heat approaches the VentRite vent, I start to hear hammering noises, and then the vent turns into a sprinkler (no rust residue in the water for some reason). The pressure in the middle pipe that takes the condensate down from dry return to wet return must be high.

I am not sure why Radiator1 does not have a vent on its dry return, and why they behave differently in terms of heat transfer to the return pipe. Is it due to the vent on Radiator2? I have read about heat traps on two pipe systems and I don’t think I have one on any of the two pipe radiators.

Can someone help to understand the cause of the spitting? Will replacing VentRite #33 with Gorton #2 fix it?
Thanks.
-Rob

JUGHNE · April 2019

Do you have steam traps on the outlet of the convectors?

bUBeHAdJoicKEt · April 2019

On the outlet I only see elbow joints. I am not sure if these have anything in them that traps the steam (these must be very old). Also, the radiators have vents. Both the radiators are heating fine. Its just that one of them is spitting water from the main vent. Would non-existence of traps result in spitting water from the main vent?

Jamie Hall · April 2019

It might well. Do both those outlets go down below the water line of the boiler before they join anything else? If so, they don't need traps, but do need the vents. If there is any way, however, for steam to go down one of those "dry returns" (they're actually, technically drips -- not dry returns -- and come back up somewhere else, there is a problem. The bottom of that problem pipe must go below the water line before it connects to anything else -- or it will have to have a steam trap on the outlet to the baseboard.

Two other questions. First, what pressure does the system cut out at? And, related, what sort of inlet valve do the two baseboards have? Are they the same? Are they both open the same amount?

bUBeHAdJoicKEt · April 2019

> Do both those outlets go down below the water line of the boiler before they join anything else?

Yes, they join below the water line.

> First, what pressure does the system cut out at?
1.5 (0.5 + 1 differential)

> What sort of inlet valve do the two baseboards have? Are they the same? Are they both open the same amount?

I have attached a picture, since I am not sure about the type of these inlets. They are the same and open the same amount. They are almost impossible to move.

Jamie Hall · April 2019

Is the air vent on the radiator with the pipe vent which spits operating properly? You either need that vent, or the one on the drip -- but not both.

bUBeHAdJoicKEt · April 2019

Yes, it is working properly. I was wondering about this as well. I can remove the main vent and see if that makes a difference, since the other radiator seems to work fine without one.

Can you please explain why we only need one? Also how does Gorton #2 work? Does it work differently than VenRite #33/#35? I have Gorton on other returns and that seems to have no issues.

I am perplexed why the water won't just drain down and instead shoot out of the vent. What would cause the pressure in that pipe be higher to push up water? And the water coming out of the vent is surprisingly cold. I would expect it to be hot.

roelandp · April 2019

The vents are there to get rid of the cold air so that the hotter steam travel faster they are installed in the wrong spot in the piping the should never be installed on top of a 90/tee they should be installed 6" to 10" before the the 90 about 15" up

Jamie Hall · April 2019

Keep in mind what the vent is doing: all it needs to do is to allow the air out of the radiation so the steam can get in. If the vent on the radiation is working, that's ample. The drip is to allow the condensate to go away. What may be happening in your situation is that the vent on the drip isn't closing, or closing as much, and remaining air coming out of it is picking up the condensate -- which is travelling on the walls of the pipe, not a nice stream down the middle -- and whooshing it out.

Try closing that vent and seeing if the radiator heats properly -- if it does, just remove it

bUBeHAdJoicKEt · April 2019

Hi Jamie,

That seem to do the trick. I closed the main vent, and I don't get the hammering and spitting. The baseboard radiator is heating ok, but it is a bit slow even with the vent fully opened. The vent seems to be breathing (from the sound of the vent it appears to also take in air). I can also hear some minor water movement (splashing) sounds as the steam moves towards the return where the radiator vent is. Few water droplets coming out from the radiator vent just before it closes. I think the baseboard needs to be re-pitched. Before I do that, I am planning to replace the vent with Gorton #6 to vent quickly to see if that helps. Do you think putting Gorton #2 for the main vent will help ?

nicholas bonham-carter · April 2019

For the same price, you could put on a big mouth vent.
Check your pressure with a permanently installed low pressure gauge, (0-3 psi, Valworx.com).—NBC

BobC · April 2019

A vent that breathes usually means something is not sloped right. Check the slope on the radiator and all horizontal pipes that feed the radiator with a level to make sure they are sloped so water can find it's way back to the boiler. If that radiator is on the second floor the radiator may have to lift up on each end to fix slope on a horizontal feed pipes.

Be very gentle when lifing a radiator so you don't break anything, I use a lever and fulcrum to raise the radiator with shims nearby to pit under the feet of the radiator - thoinn plywood strips work well for me.

Bob

Main vent on dry return of a two-pipe radiator spitting water

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