Viega FostaPex and compression style fittings

hot_rod

I have been using then Caleffi Universal pex fitting with Viega Fostapex successfully for about 8 years now.

You need to strip back the outer layer far enough for the blue, segmented compression ferrule to slide over the tube and have a small amount of tube protruding.

A slight modification to the Viega strip tool allows this to work. I removed the blade and drilled another hole, sliding the blade forward to allow the blade to strip the aluminum layer about 3mm deeper.

Unique about the Caleffi pex fitting is the insert brass that goes inside the tube has a double o-ring seal and a slight taper, so it slides inside the tube tightly and corrects any ID out of tolerance, or slightly ovaled tube.

Also a flat, captive, composite washer inside the insert prevents electrolysis, where the aluminum layer could contact the brass insert fitting if PAP tube with then internal aluminum layer is used.

The outer seal, to the manifold port is made with both a "nose" o-ring and brass taper.

Invest in the "flare nut" style box wrench which allows you to tighten them onto the tightly spaced manifold ports without marking up the brass nut, or filling the air with colorful language often heard when using a slip joint pliers.

bob eck

Hot rod are you using the Caleffi compression fittings on the Caleffi radiant manifolds?

hot_rod

Yes I am.

The thread on most manifold ports are common and standard. But the tapered end that inserts into the manifold port varies from brand to brand. We have found some other brands of manifolds that our fitting will work with.
Many radiant and tube manufacturers shop around for manifolds, so they tend to change from time to time.

The same on then top end, that actuator thread is common to many manifolds, but the actual pin height and stroke may vary. So even if the actuator screws on, you need to confirm it allows the valve to open and close fully.

Boon

This post is a lifesaver. I want to use the Caleffi manifolds and I already bought the fostapex.

Can I swap the position of the air separator & drain on the 668S1, which would allow me to flip the manifold over & turn it around; I need the piping to go up into the ceiling - not into the floor.

Boon

@hot rod is there any reason I can't use the Caleffi 682540A 1/2" PEX-AL-PEX Loop Fitting for Manifolds with Fostapex on my 6686I5S1A manifolds?

I'm guessing I can't use the 682540A with fostapex since you posted this workaround for the other compressions fittings. Wanted to double-check before I release too much colorful language (x18 fittings) into the atmosphere. Thanks

hot_rod

FostaPex has a larger outside diameter than any pex due to the aluminum layer and PE coating. If you strip that off, you end up with a standard pex OD, 5/8". The Viega crimp fittings require you to strip back that jacket also.

I have both 1/2 & 3/4 FP on my Caleffi manifold, it takes some massaging to make it work.

The standard Caleffi pex fitting works fine, the only difference between the PAB fitting is it has a brass ferrule to clamp down on PAP, which has an aluminum layer inside, much stiffer tube.

Alan (California Radiant) Forbes

Looks great, Hot Rod. One of my customers is interested in running FostaPEX using your method, but I called Viega and they said FostaPEX is designed to be used with PEXPress fittings only and there is no way they would warranty the installation, especially after modifying their tool. I'm sure the Caleffi fitting is bulletproof, but I just get a little nervous when the manufacturer disavows responsibility. My pockets aren't that deep.

hot_rod

Alan (California Radiant) Forbes said:

Looks great, Hot Rod. One of my customers is interested in running FostaPEX using your method, but I called Viega and they said FostaPEX is designed to be used with PEXPress fittings only and there is no way they would warranty the installation, especially after modifying their tool. I'm sure the Caleffi fitting is bulletproof, but I just get a little nervous when the manufacturer disavows responsibility. My pockets aren't that deep.

As expected

BobC

Corporate CYA raises it's head once again.

Bob