Cross Manifold, FostaPEX, and a really old house

lukasd

Hi, first time poster so please forgive if these are dumb questions.

I'm converting our old cast iron rads to PAP, zoning, and getting rid of the mix of black iron pipe, copper, and God knows what else currently in the system.

The old system was a McLain Weil CG5 with 1" copper running to the old 2" iron "trunk lines" in the basement. Those in turn fed what look like a mix of 1 1/4", and 3/4" supply lines to the various radiators.

My plan is to take the 1" supply/return of the boiler and run it via 1" FostaPEX to a Cross Manifold.

I've been told that the Cross Manifold 3/4 PEX crimp fitting won't work with FostaPEX, but I'm wondering if that's really the case. I understand FostaPEX is a different OD and yes I have the viega prep tool. Once you prep the FostaPEX pipe can you not just use the viega crimp sleeve over the pipe and onto a cross crimp fitting?

I attach a pic of the test crimp and the cross Manifold 3/4" fitting and the configuration I'm intending to use. Once the FostaPEX is prepped the fitting fits into the pipe and looks like I should be able to crimp it as intended. Am I missing something here?

I'm using the M18 tool with the pureflow jaws.

After speaking with the vendor I was told I'd have to adapt the manifold to use FostaPEX but I can't be the first person to try this?

Cross Manifold sweat fittings are also available, and so if what i describe above is a No-Go then I'll get those fittings, then run a copper nipple to a viega pex press fitting that's meant for FostaPEX, if that makes sense.

The Cross Manifold fittings are on each supply/return line and available in 1/2 or 3/4, pex crimp or sweat/pro press.

Anyway, wondering is anyone has used a Cross with FostaPEX, and if I'm on the right track with all this...

Thanks

GroundUp

There are a lot of folks (on this board too) that like to confuse PAP with FostaPex. FostaPex is just regular old Viega pex with an aluminum shell on it that contains an o2 barrier, which, when stripped off, leaves you with regular old Viega pex to crimp. PAP is 2 layers of plastic inside and outside with aluminum in between, and as far as I know requires compression fittings in all applications (I don't use it so I am not positive on that). Long story short, yes- you can use a regular old 3/4" crimp sleeve or ring (assuming sleeve since you have the PureFlow jaws) with FostaPex, as well as regular old 3/4" crimp fittings such as the ones supplied by Cross. Whoever gave you the aforementioned information has their wires crossed.

hot_rod

I think it's more about the manufacturers accepting other type and brands of fittings. To me if the tube and the fitting have the correct, compatiable standard numbers it will work.

I see more of the manufacturers accepting other brands of fittings, some even list name brands that are compatible.

A manufacturer may claim warranty is void if you do not use their fittings on their tube. With so many aftermarket fittings valves, and manifolds on the market it's tough to hold that line.

That looks more like a PAP fitting, they typically add O-rings to assure a better seal on the stiff PAP tube, it doesn't crimp down so easily. PEX is usually just a bare brass, copper or composite barb type fitting.

lukasd

Thanks guys. There seems to be general confusion about FostaPEX and what will or won't work, not just from amateur weekend plumbers like myself.

That fitting is described by Cross as compatible with:
- Pex (1/2”) (3/4”)
- Pex/Al/Pex (1/2”) (3/4”)

So assuming FostaPEX prepped just becomes regular old pex without the outer jackets I assume this will work.

I take the point about fittings/pipe of various makes being used together. I forgot that the ss press sleeve I showed on the FostaPEX is actually a Mr. Pex part, as I believe Viega doesn't sell those anymore (having moved to integrated sleeves in the fittings)

Cross also has the other sweat/pro press, and a PEX cold expansion fittings. They're relatively cheap (compared to the rest of all this stuff) so worst case I'll get the sweat manifold fittings and connect those to Viega fostapex press fittings the old fashioned way...

hot_rod

I suppose it is really up to Cross to bless that tube-fitting connection?

From my experience the Fostapex works with other brands of fittings and crimp rings in it "unjacketed" form. Viegas opinion may differ

Again, if there were to be a tube failure, highly unlikely, the tube manufacturer may not stand behind it.


Any listing numbers on that fitting by chance, that would indicate it was manufactured to the standard. ASTM F1807 is the common pex crimp fitting standard..

Expansion fittings are usually ASATM F1960 or F2080.

Some tube manufacturers have a standard # specific to their fittings, Rehau I believe.

lukasd

Honestly if there was a failure it would be at the manifold connection at that fitting (everything else is FostaPEX and Viega PEX Press, with integrated jackets)... As this will always be in the utility/mechanical room in the basement I can address that if it happens. Again, I expect that using a Cross sweat fitting, then a copper nipple, to a sweat Viega PEX Press fitting, to FostPEX would probably be the 'approved' way of doing this connection.

I'll take a look at any markings or notes on the fittings for compatibility. I've been meaning to also reach out to Cross and ask, probably not the first person who wants to use it that way.

hot_rod said:

I suppose it is really up to Cross to bless that tube-fitting connection?

From my experience the Fostapex works with other brands of fittings and crimp rings in it "unjacketed" form. Viegas opinion may differ

Again, if there were to be a tube failure, highly unlikely, the tube manufacturer may not stand behind it.


Any listing numbers on that fitting by chance, that would indicate it was manufactured to the standard. ASTM F1807 is the common pex crimp fitting standard..

Expansion fittings are usually ASATM F1960 or F2080.

Some tube manufacturers have a standard # specific to their fittings, Rehau I believe.

GroundUp

I have been in many a chat with Cross and have installed many a Cross manifold. The adapters you have are standard crimp adapters, and will fit ANY 1/2" nominal diameter pex tubing- not PAP. I assure you, the Viega tubing will join up perfectly with the adapters. The o-rings are a strange addition from Cross, but then again the entire Cross manifold is a one-off creation so it's just their thing.

hot_rod

Get a reamer or use your pocket knife and chamfer the end of the tube after you cut it. It's fairly easy to rip or dislodge those o-rings.

lukasd

Thanks for the info. I figured it 'should' work and installed the manifold. Crimped a 3/4" fitting to a short loop of FostaPEX on one outlet just to confirm everything works as expected. Had to install a new LWCO and brand new board into my Weil McLain but that's unrelated. Fired right up and came up to temp without any leaks... so far. I'll be sure to chamfer the pipe on those manifold fittings when I hook up the rads. That's the next step once I figure out how I'm going to run the FostaPEX.