Underfloor heating filling & pressure testing

The instructions below detail how to fill and test your underfloor pipe work and manifold directly from a mains water supply.  Using this method does not allow the addition of anti-freeze.  Anti-freeze should always be added if the system is in risk of being subjected to low air temperatures.  You would need to use a filling pump kit and reservoir tank to add anti-freeze.  Alternatively you can test using air pressure, but remember to temporarily remove and plug off the automatic air vents first.

Filling your system directly from your mains water supply

For this you will need mains water supply and a garden hose with threaded tap connections.  Follow the step by step instructions below.

1. Open the fill/drain point valves on flow and return manifolds (turn square head anti-clockwise, a key for this is built into the cap).
   
   
2. Shut both red and blue handled isolation valves.
   
   
3. Close (turn clockwise) all flow meter valves on flow manifold.  To do this unclip the red plastic locking sleeve situated on the flow meter and turn the clear plastic tube accordingly.
   
   
4. Close (turn clockwise) all white plastic manual valves on return manifold. (top manifold block).
5. If you have a standard control combimix manifold or an extension pack manifold, close top valve on pump fittings (slot indicator horizontal).
6. Starting from left side open the first group's valves on flow and return.
7. Connect mains water supply to fill point on flow manifold and another hose to the drain point on the return manifold.  This latter hose should be taken to where the water can drain away safely.
   
   
8. Unscrew small caps on auto air eliminators so they are loose.
   
   
9. Turn on water–the water will enter the flow manifold and go round the group you have opened until it comes out the drain point on the return manifold.
10. Let this water run out for 2/3 minutes to get rid of any air.
    
    
11. Close the valves for the group you were filling and repeat this process for all groups until they are all filled.
    
    
12. Still with the mains water pressure on, now go back along the manifold opening all the group valves on return and flow manifolds.
    
    
13. If standard control combimix manifold or extension pack manifold, open top valve on pump fittings (slot indicator vertical).
    
    
14. Close (turn clockwise) drain point valve on return manifold, then fill point valve on flow manifold.
    
    
15. You now have a manifold and pipe filled and pressurised to mains pressure.
16. Turn off mains water supply and disconnect fill and drain hoses.
    
    
17. Check for any leaks at manifold and check that pipe is free from any kinks.
    
    
18. If your manifold has a pressure gauge take a note of the pressure.  If it drops to zero you have a leak, if it drops and stabilises that is fine.  Close caps on auto air eliminators.
    
    
19. You can now go ahead and lay the rest of the floor, keep monitoring the pressure at the manifold.  The pressure will fluctuate with ambient temperature.