Reducing radiator noise: is an air eliminator the answer?

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Old 02-09-14, 09:43 AM
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Reducing radiator noise: is an air eliminator the answer?

My 3-story house (built 1926) has the original hot water radiator system with a Munchkin boiler (installed about 12 years ago). I had always been bothered by the constant drone of water rushing through the pipes and thought it was just a fact of life heating hot water with a boiler. Bleeding air didn't help.

Then, a couple of years ago, I had to drain the system in the summer to renovate a room. I was delightfully surprised that after refilling the system that it was almost silent in operation--at first. Over the next couple of weeks, however, the rushing sound got louder and louder, until it's as loud as it was before. I tried bleeding air but that didn't help much. I did another renovation last summer and the same thing happened. I loved the silence and want it back!

I read in This Old House magazine about installing an air eliminator (air separator) on the supply pipe close to the boiler. Is this the answer to my problem? I don't want to pay for the device and installation unless it's going to work.

A final note: there were some radiators removed many years ago (on the first floor and basement). I suspect the pipes were capped rather than removed, but I don't know for sure.

Thank you for your responses!
 
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Old 02-09-14, 11:11 AM
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Rushing water sounds is a sign of air it the system. What do you have now for air removal and what pressure are you running at.
Are there any pics of system.
 
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Old 02-09-14, 02:06 PM
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The only thing I have for air removal is bleeding at each radiator. It runs at 20psi

I've attached a photo of our boiler in the basement.
 
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Old 02-09-14, 02:35 PM
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P,

What do you have for an expansion tank?

Is that 20 psi cold or hot?

When you bleed the rads do you start with about 28 lbs and maintain that until the end and then drain back to 20 or do you let the pressure go down until it feeds back in?

The goal when bleeding is to not introduce any fresh water or as little as needed because fresh water brings air with it so every time the boiler refills it brings another batch of air and you're defeating your whole purpose of bleeding.

The pics are a little fuzzy. Is that 2 pumps I see?.

If you have a bladder type ex. tank a spirovent would definitely help. It would remove the lions share of the air nd any future air on a continuous basis.
 

Last edited by NJT; 02-09-14 at 04:29 PM.
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Old 02-09-14, 03:49 PM
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Is that 2 pumps I see?.
Looks like to me also... probably set up with the boiler on secondary loop, I think I see closely spaced tees near the upper left.
 
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Old 02-09-14, 10:31 PM
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Thanks for your replies!

Yes, there are two pumps. There's an expansion tank (visible in the two additional photos taken from different angles). Someone suggested slapping it to determine if it's water-logged. I did this but couldn't tell if it was water-logged or not.

The system is running between 18psi cold and 20psi hot. I don't think I can bring it to 28psi without water pouring out on to the basement floor (perhaps there's a pressure release in the boiler at 25 psi?).

Anyway, I don't think there's much air to bleed out of the the radiators--at leas not so much that the pressure goes down significantly. But to make sure I'll try bleeding it again tomorrow when the system is cool.

It sounds like an air eliminator (Spirovent) might be what I need.
 
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Old 02-10-14, 07:40 AM
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Someone suggested slapping it to determine if it's water-logged. I did this but couldn't tell if it was water-logged or not.
Of course you couldn't... it is a completely pointless test.

The system is running between 18psi cold and 20psi hot. I don't think I can bring it to 28psi without water pouring out on to the basement floor (perhaps there's a pressure release in the boiler at 25 psi?).
Safety relief valves are typically 30 PSI.

Your pressure gauge may not be accurate.

It sounds like an air eliminator (Spirovent) might be what I need.
No... systems with your type of expansion tank should NOT have any automatic air valves installed.

That type of expansion tank needs to be piped properly so that air traveling through the system is caught and directed back to the tank. It probably isn't.
 
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Old 02-10-14, 09:45 AM
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The reason I asked about the expansion tank is exactly for the reasons trooper gave.
The worse thing you could do is put in a spirovent.

If you had a bladder type tank, like an extol, that's when you would install a spirovent.

If your relief valve is going off @ 25lbs you may want to check your gauge. As trooprt stated, relief valves are set for 30 lbs. You may be running at 13 instead of 18 and in your case I think that would be too low, which could account for the water sound.
 
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Old 02-12-14, 10:50 AM
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I bled the radiators, filled the system to 28psi (cold) without any leaking, let the system run and cool back down. I bled a small amount of air from the radiators but not much. The rushing water is just as loud as before.

Trooper said that
That type of expansion tank needs to be piped properly so that air traveling through the system is caught and directed back to the tank. It probably isn't.
How can I tell if it's piped properly? Here's a picture of the expansion tank from another angle:
 
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Old 02-12-14, 11:38 AM
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Two things with a steel tank is
1) that yellow ball valve must be fully open at all times except when draining the tank.
2) the pipe from the boiler to the tank should be a min um of 3/4" pipe.

Looking @ some previous pics, is that tank connected to the returrn line in front of the pump.
The tank goes on the supply side so the air can go into the tank. With it installed like you have it, it looks like you're pump is pulling water out of the tank. Air can't get in with that set up.
That's if I'm looking at the pics right. And also, is that another 1/2" line going to the boiler on that same line.

Your expansion tank goes from the supply to the tank with 3/4" pipe on a slight pitch toward the tank with nothing else connected to it. The isolation valve is always open unless draining the tank.
These tanks are generally piped off of an air seperator installed in the supply line.

No other air devices are needed. The tank is there to accept the air and heated water.

That tank needs to be repiped properly.
 

Last edited by spott; 02-12-14 at 11:53 AM.
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Old 02-12-14, 10:05 PM
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spot
The tank goes on the supply side so the air can go into the tank. With it installed like you have it, it looks like you're pump is pulling water out of the tank.
The expansion tank defines the Point of No Pressure Change and all pumps should pump away from the PoNPC into the system.

This system has no way of retuning air to the tank.

To fix this system I would:
1) Install IAS or similar ( 3/4" top port required ) between the boiler and the system pump.
2) And optional ATF- on the expansion tank.

Please read:

"Five Good Reasons to Pump Away!" [PDF]

"Now letís see how hydronic heating tanks work"

"Proper Air Management in a Hydronic Systems[sic]"

Installing Expansion tank using B&G ATF [PDF] See drawings starting on page 4

Air control examples:

3/4" top port (1-1/2" to 3" only) IAS Inline Air Separator
3/4" top port All EAS Enhanced Air Separators
 

Last edited by HeatWorm; 02-12-14 at 11:13 PM.
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Old 02-13-14, 04:56 AM
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Yeah, what he said, pumps on supply. You need to add pressure to the system to break up the air bubbles making them small enough to get back down to the boiler. This only happens pumping away from the expansion tank. Pumping towards the tank the system pressure goes down and the bubbles get larger and more buoyant. Also must have air separator unless I am missing it.
 
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