How to purge air from heating system?
We have radiant heat & are finding that the pipes still have air bubbles that are trapped in a few spots. Beyond flushing air out by pushing more water in at street pressure (through & out to the sump), are there any other tricks for removing all the air? I am finding that just pushing…
We have radiant heat & are finding that the pipes still have air bubbles that are trapped in a few spots. Beyond flushing air out by pushing more water in at street pressure (through & out to the sump), are there any other tricks for removing all the air? I am finding that just pushing water through is probably effective but is very very slow and am wondering if there is a better way…
Should I get a plumber to do this? Is there any particular equipment that helps?
Thanks again. Appreciate the feedback.
The system does seem to be effectively eliminating air bubbles from the incoming street water as I can run the water back out to the sump bypassing the floor loops and not see any bubbles. I only see bubbles if I run the water through the floor loops. From what you wrote, I expect I have to just continue to purge the system for longer (I have been avoiding this as it seems to be a prodigious waste of water (if there were a better way). I have some pressure valve that lets me push the pressure up to ~30psi and it does help.
I am pretty confident that the overall design is right given it was written up by an experienced heat engineer recommended by Warmboard (the company who manufactures the radiant heat floor system we used). We have circulation pumps that match the spec. My problem is that the plumber who installed the system has introduced at least 1 problem (over tightening joins) and hasn’t been as communicative/helpful as I would like. I wasn’t confident that I wasn’t missing something…
Yes, displacing the air with water is the only way to fill the tubing. There are some tricks to purging a difficult system, but remember that fresh water always contains a new supply of air and purging any system is only a temporary fix.
Every closed system (like yours) needs some device or arrangement of piping installed which will separate air from the water’s path of travel or expel it from the system altogether.
A well-designed hydronic system will include one or more automatic air elimination devices at the boiler.
My suggestion is to raise the pressure in the boiler to a few pounds below the relief valve setting (usually about 30 psi). That will compress the air bubbles making them smaller and easier for the system to deal with.
Run the boiler and see if the heated water circulates more effectively under the higher pressure.
If some loops work better than others, close off the good ones and see if you can force water through the others.
If not, try purging these loops again with the good loops isolated or valved off.
I read that you’re seeing air bubbles in the water, but very often bubbles aren’t enough to completely halt the flow of water. What you need to be concerned about is a slug of air, or empty section of piping.
I rather suspect you’ve got a flow issue caused by design or pump selection instead.
Hope this helps.
Master Plvmber – thanks for responding.
As I flush water through the system, draining into the sump, I can see bubbles pushed out. We do have one loop in a hallway that is probably not working effectively but I am not sure as the doors aren’t yet sealed well and so it gets colder there (though I have pushed water through this loop after isolating it, but not to the point where no more bubbles come out). The floors in the rest of the house are obviously warm and the house is a comfortable temperature.
Is flushing the pipes with water the only effective way of getting the air out? Are there any tricks to help get the air out?
How long should it take to flush all the air out in this way?
I believe that a few of the rubber washers at the join of the pex to the manifolds are damaged from over tightening to the extent that the washers need replacing / are dripping water (very very slowly but visible). While I will get this done, I am wondering if this sort of thing could allow air into the system in the meantime.
What are your reasons for thinking “the pipes still have air bubbles that are trapped in a few spots”?
I hope it’s not cold spots in an otherwise warm floor…