I've had sub-floor heating installed a month ago and I think I have a problem with the air in the installation, because there are some rooms that don't reach the desired temperature.

The plumbers tried twice to take out the air by locking each circuit separately, but it's still not working. Now they told me to let the circuit pump running while turning off the central heating for a week. It doesn't make any sense to me and I'm pretty sure they aren't very good with this.

Here's how it looks: enter image description here

There's 8 circuits and a Wilo Yonos Para pump that cools down the water that comes from the central heating by pumping the returned water in the main pipe (English is not my native language and I don't know how to formulate it very well. Sorry for that).

Basically the problem is that I have 3 rooms upstair (2 bathrooms and the dressing) that don't reach the desired temperature of 20C even after one week. The bigger rooms (bedrooms) reached it in 1-2 days.

3 Answers 3


Your hydronic floor heating system could have several problems. You'll want to troubleshoot to narrow it down:

If you hold the pipe that returns from the upstairs room, is it warm like the other pipe? If so, then there is circulation happening. In that case, you can try to balance the system by directing more flow into that pipe. This is done by turning those adjustment valves on top of the return manifold. You would turn them down for the other rooms, and turn the up for the colder room. If this still doesn't help, then you could add insulation to the upstairs rooms. If nothing else, maybe your upstairs subfloor is more thick or more insulating that the downstairs rooms which are working. You could try insulating from below with reflective shielding to direct all the heat up, but this would be possible only if you still had access to the underside of the subfloor.

There should be no air in the pipe, because that will prevent circulation or make the pump inefficient or damaged. Air should be completely flushed from the system by bleeding one line at a time with the pump on. If you grab the return pipe from upstairs and you feel no heat while the system is running, then you could have a lot of air, or perhaps a kink in the line, because there is no circulation coming through it.

  • I've just read about the adjustment valves and I might give it a try. Should I wait for a week like the plumbers said or just go for it and try it with the valves? Commented Oct 31, 2017 at 19:14
  • 1
    I would give it a try. If it doesn't work you can always change them back to what they were before the plumbers come back.
    – freshop
    Commented Oct 31, 2017 at 19:16
  • Ok, I will give it a try tomorrow. Now that I've had the central heating turned off for a day, should I set the water temperature low when I turn it back on or can I start directly with 35-38C ? Commented Oct 31, 2017 at 19:23
  • 1
    I can't think of any problem with starting hot.
    – freshop
    Commented Oct 31, 2017 at 19:50

Is your house a multi story house and if so how many floors are there? How did they run the heating tubing for the upper floors? You said that 3 rooms upstairs do not get warm. Do any of the rooms upstairs get warm? Are the upstairs rooms larger than the rest of the rooms? If you can check, does all the water in the piping, both the supplies and returns, in all 8 zones, get about the same temperature? Did the installer give you any vents or a way to vent the air in the heating zones for the upper areas? What is the pressure reading on the gauge I see in the bottom picture and how many feet above the gauge is the highest point in the heating tubing? By running the pump continuously the contractor is hoping all the air will collect somewhere it can vent or be vented

  • My house only has one floor + the ground floor. The ground floor works great. Two big rooms get warm, while 1 big one and the smaller ones don't. He didn't give me any vents, they come to do the venting themselves ( they tried it twice). I not longer have that gauge as they took it off after testing the installation. They said the air will be vented by the automatic vents, which you can see on the right. Commented Oct 31, 2017 at 19:09
  • . It is very hard to trouble shoot your system from where I live north of Pittsburgh, Pa, however I would have added valves to each of the 8 zones (tubing runs) so each zone could be vented separately; left a gauge on the system with an indicator as to the lowest allowable pressure; and added more vents both automatic and manual. I am not saying that they did any thing wrong, however something is wrong since the heating is not working as it should. Make sure that the system works as it should before you release them from their responsibility and that they show you how to vent the system
    – d.george
    Commented Nov 1, 2017 at 9:50

Kick up the water pressure a few pounds. Then try the manual venting again.
Happy Venting P.

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