Purchased a home which has a floating floor radiant heating system installed in the basement. I am looking to remove the system as it was poorly designed and installed. I've closed off the fresh water supply and drained the gas water heater already. I've also closed the shutoff valves to and from the supply/return manifold. How do I completely drain the water from the pex tubing that runs under the floor to each zone before I tear out the floor? Below is the manifold.

radiant heat manifold

2 Answers 2


I would approach this as if it was a sprinkler system... with compressed air. If you can, work each circuit individually. If not, work the longest or furthest ones first.

You could also simply use a wet vacuum. You'd need the opposite end of the circuit open to the atmosphere, of course.

  • 1
    The caps with the white straps on the left ends of the manifolds are for draining.
    – longneck
    Jul 21 at 14:22

The far end of the water circuit needs to be open to the atmosphere. Open the other end and let it drain but the drain end needs to be at a lower elevation than the far end. A vacuum is formed naturally, it will drain completely. It works much the same way as when you drain water out of a garden hose, if you elevate the hose above the discharge drain end, the water comes out of the hose because of vacuum. There will be some residual water but you'll be able to deal with that.

  • 1
    Can that be achieved by connecting a garden hose to the return drain valve on the manifold and opening the drain valve on the supply side?
    – rome
    Jul 21 at 14:26
  • As long as the discharge end is lower than the vent end. The more water level difference between outlet and drain, the faster it will drain.
    – RonT
    Jul 22 at 17:20

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