Home>Discussions>INSULATION & HVAC>Water Basebaord Heat - Noise Issue
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Re: Water Basebaord Heat - Noise Issue

Yes Winston, I recommend bleeding an upper level bleed valve/spigot when the circ is off, and preferably when the boiler water temp is warm or cold; when the boiler water is near its maximum of 170/180 degrees, it has expanded in volume approx 4% (water always expands 4% of its volume when heated).

You will be able to see this on the boiler gauge temperature/psi needles, which will fluctuate from a cold reading of approx 90 degrees/12-15 psi, to approx 170/180 degrees/20-25 psi---you may well know that there is a near-boiler automatic safety valve called a pressure relief valve (PRV) that will automatically open & spill some water on the boiler room floor if the pressure exceeds 30 psi---this is a safety device, and the cause of the excess pressure has to be found, but it is no need for alarm.

Your ideal goal in the "bleeding process" is to have it so you hear hissing when you open the spigot, then see a healthy dribble of water come out, and the spigot shutoff closes completely with no drips-----this indicates the piping system is completely filled with water, & that the near-boiler pressure reducing valve is properly set (this valve is adjustable) for your particular heating system---if the psi needle on the boiler gauge reads 15 psi (as you stated) when the boiler water is cold, this sounds like an ideal psi reading for your system, but the true test is if you can get a dribble of water out of the upstairs spigot-----quite often a pocket of air develops at the top of the piping system because the boiler water can't quite get up to the upper baseboards (this pocket of air then gets mixed with the piping water when the circ comes on & you get noisy pipes) ---in such a case the pressure reducing valve is slightly adjusted to perhaps 17 psi so the water in the piping system completely fills all the upper level baseboards--the system then quiets down because there's no air left in the circulating pipe water.

Re: Water Basebaord Heat - Noise Issue

Ok, thanks. I will report back after I give it a try.

Re: Water Basebaord Heat - Noise Issue

Just thought I would report back on my progress...

I tried just bleeding the air from the top of my system with no luck. I had to turn the faucet quite a bit to get the required flow to purge the air - this had the effect of purging more water too.

I ended up repeating the following steps about 5 or 6 times:
1/ Slightly overfilling the system
2/ Letting the system run for a cycle
3/ Wait a little while
4/ Purge air/water (usually about a gallons worth before air stopped coming out)

Bit by bit I was able to get all the air out and (so far) now have a silent system.

Thanks for the help!


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