In floor heating

[slowTA]

Over the course of the few years its been taking me to plan my garage, I've seen a few posts here where people state that fastening the in floor PEX to the insulation or rebar is critical so it doesn't float to the top. I've also read that the PEX should be pressurized so it doesn't get crushed by the weight of the concrete (it also serves as a good way to check for leaks).

Is there something wrong with filling the PEX with the coolant/fluid of choice then pressurizing before the concrete is poured? I imagine bubbles could be a concern, so I would consider adding the pump on a switch to circulate fluid and get all the bubbles up to the expansion tank. Obviously this would transfer some cost from the 'after the pour' phase to upfront, but in the end it wouldn't be a waste of money.

The one downside I can picture is if the concrete crew punctures the PEX while pouring and the area floods with coolant. So there would be a mess to clean up along with long term concrete concerns instead of just patching the PEX and re-pressurizing the system. But I've never worked with PEX, so I have no idea how delicate the stuff is.

 

[Kev In]

I have installed PEX for infloor heating a few times. I have used the plastic barb clips into the styrofoam to hold the pex in place. My rebar is on top of the pex. Use poly under your styrofoam. Use 2” styrofoam or thicker if you can afford it. They make 4x4 foot sheets of styrofoam that has channels in it to hold your pipe straight with nice radiused bends for your loops. You can also tie pex to rebar, just ensure that nothing sharp that can cut or puncture your pex. Pex is pretty durable stuff. If you are installing the pex yourself, make sure you have a spool holder to pull the pex off.

I have 3500 sqft of in floor heating in my house and it works like a charm.
I have installed pex unpressurized in a garage with no issues, but you should pressurize the pex with air and put a pressure gauge on for 24 hours before you pour to ensure you you don’t have a leak. It also allows you to monitor your lines during the pour. You could use coolant, but I would lean toward air.

Good luck on your garage build.

 

[Jon_E]

The weight of concrete is 150 pounds per cubic foot, which works out to just over a pound per square inch for a full 12" thickness. Assuming you've got 3" of concrete over the top of your PEX, that works out to about an eighth of a pound (2 ounces) per inch of PEX tubing. No way concrete will crush it.

Pressure testing is just to check for leaks. Will not protect the tubing from punctures or crushing.

 

[road_king]

You want to pressurize pex with air before concrete to be sure there are no leaks. If there are, easy to address prior. No benefit doing so to protect from weight of concrete.

 

[slowTA]

Thanks for all the info, how much pressure would make sense? If I were to guess, I would say 30 psi.

 

[kj_mustang]

Air pressure does help protect the pex from the concrete workers standing on it during the pour.

 

[analog]

Our local inspector wanted to see 50psi in my pex tubing. It held that fine for several days while I waited for inspection.

I also kept it pressurized during the pour and watched the gauge to see if the concrete guys accidentally damaged anything.

 

[rburke65]

Well the Pex tubing is really tough to puncture. I didn’t worry about it when I installed my tubing.