radiator vent sound

vinceM

Good afternoon all.
Question about what "sounds" are acceptable coming from a rad vent. I have a rad in a bedroom on the second floor that is always the last rad to heat up. While this rad is still venting all the others in the house are already hot. I have to admit I'm still not clear on what a "hissing" sound(at least in radiator terms) is. All my vents make some kind of sound but all the other rads heat nicely. One thing that is distinguishable, is that all the other vents release air "smoothly" and "linearly". The other vent sounds like someone is exhaling rhythmically through their mouth with slightly pursed lips... if that makes sense..?? Eventually though, the rad does heat up but it's the first to cool. Also, connected to this situation, as the rad is warming up a clearly audible "rushing/rumbling" or surging of water can be heard from below the floor right at the inlet. It sounds like water is trying to climb the riser to the inlet valve.
Any thoughts??

BobC

It sounds like you have a pipe or radiator that isn't sloped right. Everything has to have some pitch so water can find it's way back to the boiler. Put a level on the radiator and make sure it slopes back to the input valve. Make sure the radiator feed pipe in the cellar is sloped back towards the boiler.

There may be a short horizontal pipe under the floor that you can't see because it's sandwiched between the ceiling and the floor. That short pipe could be pitched wrong, one cure is to lift the entire radiator up by 1/2 to 3/4", making sure you keep some pitch back towards the valve. Lift the radiator slowly and carefully using a lever and shim the feet up with shims.

Bob

Jamie Hall

Somewhere in the runout to that radiator you are trapping condensate. You need to check the pitch of every length of pipe, however short, that leads to that radiator and make sure that the whole is pitched to drain back to the main.

You also need to make sure that the valve to the radiator at the inlet is fully open, and that the radiator itself is slightly pitched back to the inlet.

That should help with the rhythmic sound and the water sounds.

Then, to get better balance, you may need to look at both your main venting, to make sure that the main(s) get steam all the way to the ends quickly, and at the venting of all the radiators; you may need to slow some of the more eager ones down a bit.

JUGHNE

Being how it is on the second floor...right? are the pipes exposed on the floor below it or perhaps run up an inside wall and then horizontal to the 2nd exterior wall where this rad might be. They would be above the ceiling with some length to them.

BobC's plan might correct that as the original support was sometimes lacking and over time iron pipe will sag under it's weight and devolve a "belly" (like I have done with age )

vinceM

Yes, the rad in question is pitched back towards the inlet. I've been playing around with the degree of pitch but it doesn't seem to help. Based on recommendations from previous posts, I have replaced the previous larger Jacobus vents on the second floor rads with Jacobus (Maid-O-Mist) #5 and #6 depending on the size of the rad. This particular rad has a #5 vent. This rad is 26", 9 section, 5 tube.
I have been (mentally) struggling with the run-out pipe slopes in the basement. It's an old system and I, think??, the pipes aren't all pitched correctly due to sagging. I'm not sure if what i'm seeing is supposed to be that way. In some places the pipes pitch towards the boiler, in others there level and in others the pitch away. What confounds the issue, is that the pipes branch off in different directions. I liken it to a spider web of pipes. it's difficult to get a handle on which pipe should pitch which way. I know the mains should pitch towards the wet returns as they reach their terminus.
It's the T'd branches in-between that tie one line to another, NOT, the Ts that branch directly up to the floors above that give give me trouble.
My question is, from the point where the pipe leaves the header, in which direction should it be sloped along its' entire run. Including any and all branches.
I have attached a few pics of the boiler to possibly help illustrate what I'm describing.

BobC

In a single pipe steam system the pipe from the steam main to the radiator must all pitch back towards that steam main, don't trust your eyes use a level. You can stretch a string along sections of the main to check for sags in the piping.

Any mis-sloped pipes and sags have to be corrected.

Bob

Fred

On a One pipe steam system, parrallel flow,
1. Mains should pitch away from the boiler,
2. Branches should pitch towards the Main it branched off of, unless there is a drip leg at the end of the branch. Then it should pitch towards that drip.
3. Radiator run-outs should pitch back towards the main or branch it ran out from.

vinceM

Thank you for the responses. I will do as Bob recommended and lift the whole rad making sure to keep the proper pitch. I'll re-evaluate the pipes in the basement for proper pitch.
To confirm that I understand , NO "black pipes" that are above the header or in the immediate vicinity of the boiler should be pitched in a way that would allow condensate to flow back to the boiler..??

BobC

All radiator pipes have to pitch back towards the steam mains unless there are drips back to the boiler return. The steam mains have to slope back to the boiler if it's counterflow or towards the wet return if it's a parallel flow system.

Bob

Fred

On a Parallel flow, no steam carrying mains or branches should pitch back to the boiler. Branches pitch back to the mains, mains pitch in a direction away from the boiler, until the end of the Main where they might turn into a dry return (after the last radiator run-out. At that point, they may turn and head back towards the boiler, pitched in the direction of the boiler until they drop down into a wet return (vertical pipe that drops below the boiler water line and then into a Hartford loop, back into the boiler. If properly plumbed, all of that pipe is "black Pipe" above the water line and may be copper below the water line.

vinceM

Ok. I have copper wet returns that drop down from the mains right after the #2 Gorton vent and run along the basement floor. So I have a parallel flow system.
Thank you Bob.

vinceM

Thank you Fred

vinceM

Yes. There is a Hartford Loop