I have a single zone in my house with forced hot water only heating on one side of the house. What am I doing wrong? I have bled the pipes many times and still not heat on one side of the house

  • Did it ever work, or a has it always been like this?
    – Ecnerwal
    Commented Dec 21, 2015 at 3:03

4 Answers 4


99.5% you need to bleed somewhere you haven't found yet, or you need to bleed more. It's almost always an air bubble.

0.3% there's a misadjusted valve to blame. If you don't know what a balancing valve looks like it may not be obvious that it is a valve.

0.2% there's an actual blockage. I've seen a 1/2" pipe elbow that had less than 1/16" space for flow due to some VERY enthusiastic soldering (it was nearly plugged with solder), in the bizarre examples line. But this is chasing the tiny odds.

I happened to have camera and the fitting in question from my junk (perhaps "plumbing trophies") box and recall that I want to show it. Trigger warning "terrible plumbing."

Copper pipe elbow plugged with solder - image by me

The little gap at the bottom of this picture was the only passage for water in this fitting.

Another possible blockage - if it got really cold before you turned the heat on, there's a frozen section on the one side. In some houses that's more like 25% odds due to terrible heating system design and poor insulation.

If you can't sort it yourself, calling in a pro can make sense before things DO freeze up.

  • "Enthusiastic soldering" 😆 But the solder keeps disappearing into the little crack, shouldn't I just keep feeding it more?
    – ArchonOSX
    Commented Jan 20, 2016 at 9:27

Are you sure the circulation pump is actually circulating? You might have a very slow gravity induced flow. If so you'd likely have each room down the line receive somewhat less heat than before.

  • The problem I have I don't believe is gravity flow. I have a 1" feed that goes down the middle of the house, 18" before the end of the house there is a tee that goes to two 3/4" pipes. One way goes to the front of the house the other to the back of the house. The front has heat the back doesn't.
    – user46855
    Commented Dec 21, 2015 at 1:02

Sounds like you have a hard-to-find or hidden shut-off valve in the pipe for the back of the house that someone closed to save money. If the front of the house is heating then the pump is working, which means it is not air-locked and you separator is working fine.

If you have vertical radiators, there might be a bleed valve at a high point in the back circuit or on a radiator that is full of scale or needs replacing. If you have perimeter heat there probably isn't a bleed valve since you have a pretty flat system. So, if the back circuit was unrestricted it should have water flowing through it.

So, I believe you have a major restriction or a closed valve.


Fill the system with water. If you're bleeding & just not hearing air purge & seeing no water, then it's very low on water. On the other hand, it could be that your expansion tank's bladder is blown or that you just need to pump it up, usually just to 7-psi or so.

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