View Full Version : water loss in underfloor heating

10-21-2005, 10:43 AM
Whenever I fill up my system to full, ater a couple of days the guage has fallen and after a couple of weeks it's almost empty again.But i dont see anywhere where the water could be leaking out. Does anyone know if this means i have a leakage in the system or whether there could be another cause??
Thanks for any help

10-21-2005, 11:19 AM
Even without knowing the size of your system, I expect that that is a lot of water to lose over that period of time. You must have a leak, but you would probably see some indication of leak with that amount of water being lost. Is your pex imbedded in a slab on grade? What are the facts? A slab could make the leak less obvious. If you do not see water around the boiler or the tubing going in and out of your manifolds, it must be in the field. I have heard of people using heat detection devices such as those used by fire departments to identify a radiant leak. Good luck.

10-21-2005, 12:03 PM
sorry dont really understand all the techinical terms!! its a terraced house & 2 floors have underfloor heating and the water runs in plastic tubes under the tiles ...i think..or could it be that the meter isn't working properly??Thanks again

Gary Swart
10-21-2005, 05:46 PM
The "plastic" pipes are most likely PEX. Here's what you should do. Turn all water users off. With the water off, go to the meter and observe the dial. It shouldn't move even a hair. Continue to watch it for several minutes. A slow leak in a pipe would not cause the dial to spin like Wheel of Fortune, but it would show movement in a few minutes. If it is a leak, you will require professional help.

10-22-2005, 07:28 AM
thanks alot Gary I'll try that

10-22-2005, 07:35 AM
IF this is a heating pipe, as you indicated, then it is not connected "directly" to the water system so a leak in it would not cause any movement in the water meter. Is this a British heating system? If not, why do you have to fill the system manually? There are a lot of unknowns here, and the only way to give a good diagnosis would be to go to your house and check the system personally. Failing that you probably need a heating technician.

10-23-2005, 01:42 AM
thanks..yes you are right its not connected to the mains i have to fill it up myself - its a German system actually (live in Germany) and the problem is anyway that the loss of water is not THAT dramatic ..but the meter in the heater shows a drop to about halfway after a week and then it goes down more slowly.
thanks for your help

10-23-2005, 07:35 AM
One possible cause is that when you add water you also add the air entrained in the water. When the water is heated the air is released, and if you have any type of air "eliminator" on the system, that will decrease the volume and thus the pressure. But logic says that even that should eventually be cured as you add less and less water to make it up. So, the only other good possibility is a leak, but you really need a local plumber who is familiar with that type of system to check it.

10-23-2005, 01:55 PM
If the valve you manuallyuse to fill the system leaks and there is no check valve to prevent backflow, having lived in Germany for a little while, when things hiccup, the decreased pressure in the mains could allow a little water to flow out of the system. Probably a slim chance, but possible. If this were true, though, it would probably also leak water into the system as well since the mains pressure is higher. Just a thought (sometimes they aren't very good ;) .

10-24-2005, 08:51 AM
There were systems similar to what you have that had an open system, in as much as there was a pipe that returned to the area near the boiler. It was returning from above the highest point in the heating system.

Besides looking at the gauge, you filled the system till you got water returning
from this overflow. That meant the system was full. So you had to tend to the water level.