I use clear aquapex for plumbing and was wanting to use it for underslab radiant heat.  has anyone used it for radiant and is there any difference from blue and red pex tubing.

pex pipe is made of polyethylene Wirsbo is a brand name that has a cross linked molecule that makes the wirsbo remember its own shape,hence the name pe for polyethylene the x is the factor for cross linked molecules.


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SIPs

Yes there is quite a difference in types of pex tubing. Radiant heating is a closed loop system and it is very important to reduce the free oxygen content of the fluiid within the tubing. All radiant systems should you a pex with a oxygen diffusion barrier. Oxygen causes failure of pumps and plumbing components if not properly dealt with.

If you have iron/steel components.

PEX colored for DIY plumbing and brand recognition.

Barrier PEX is most common but non-barrier is used extensively for commercial systems, as it can be 25% cheaper than the various barrier tubes. Oxygen permeation is relative to temperature so a barrier or heat exchanger may or may not be required.

Wirsbo is now Uponor and beyond the barrier issue is the UL listing; one for potable water, one for space heating. The PEX tubing must be marked for the purpose. Many manufacturers now list both on their PEX pipe but Uponor does not.

At typical residential radiant heating operating temperatures a barrier PEX should be used to protect ferrous metal components such as pumps, cast iron boilers and expansion tanks.

oxygen barriers also protect glycol additives from breaking down. I recommend only oxygen barrier pipe for that reason... unless you're in a region that never freezes, you never know if you are going to HAVE to add glycol. A sick relative in another state, sudden changes in employment... lots of things can happen.

I beg to differ.

As Ziggy puts it " The only good thing about anti-freeze, is that it doesn't freeze.” In fact it is in large commercial heating and snow melting systems that an oxygen diffusion barrier is often foregone, the reason again is cost. The other factor is that these systems typically operate at sub-body temperatures (or should) and oxygen diffusion is a factor in permeability, the higher the operating temperature, and the higher the rate of diffusion.

For example, I replaced a non-barrier Polybutylene tubed driveway snow melting system a few years ago that was installed in 1977. After close inspection it was clear that the pipe had frozen for neglect of the antifreeze, but the tube, boiler and trim were otherwise serviceable. When I started in the 80's it was all polybutylene and we did see some corrosion problems, normally manifesting themselves in thin diaphragm expansion tanks rusting from inside out to failure; even so, these instances were very rare given the million feet of pipe or so that we had in the field.

Our simple answer was to use a potable water expansion tank and bronze circulators. As our main line of boilers was stainless, this was not a factor. It is now common for all boiler manufacturers to demand the use of barrier PEX sighting possible component failure. The real reason is misapplication and the potential for corroded elements to clog critical flow paths such as impellers, checks and globes.

I almost never use anti-freeze in residential hydronic systems, as it always cost more to install, operate and maintain and never, by the way, needs the accepted 50/50 mix, south of Yellow Knife Canada. I prefer a simple and reliable freeze alarm (integrated into many of our security/HVAC controls now) and I keep my homeowner’s insurance current and not willing to pay twice and forever.

As a rule I certainly agree that most should pay a little more for the DIN 4726 barrier, as on the small scale, the extra cost is of no consequence.

snowmelt may be an exception.

However, not freezing is a serious design requirement, and in the case of unoccupied homes, it's the only way to be sure, pure and simple. and many homes can go from "occupied" to "unoccupied" in a hurry. Those homes should get glycol. usually a 20% mix is adequate, but of course that's climate dependant.

I like freeze alarms but they are not foolproof. if the house has a proper alarm system (i.e., it will alert when it loses communication) that's a different story, but typical freeze alarms must dial out on a problem. that's a critical failure vector.

The voice of reason, but some new alarms use a dedicated cell phone so no worries. I might go for 20% but how many know how to get there or the difference between flow and burst?

you ever tried to get cell reception during a storm in the woods?