Viega FostaPex issues

kcopp

Hi All.

Someone may have posted awhile back about Viega FostaPex O2 issues….

This product was on the market for years and it had some nice benefits. Solid, no drooping, bendable to a point, simple connections.

Viega pulled it from the market for some reason a couple years back No explanation. Local rep had no explanation.

Now i am wondering in O2 ingress was the reason and the higher ups have kept this under wraps to allow plausible deniability.

I was called for a no heat call last week. Circulator was done. (Grundfos 15-58).

System is an Adu installed in 2009. 3/4" Fostapex. 10 feet on HW baseboard, kick-space heater.

When I went to purge out the loop I was stunned at how little flow was going through the piping. To attempt to force the flow I cut in a second boiler drain and street pressure (65psi) to blow out any junk.

I was surprised to see sediment in the bottom of the piping.

When purging I got A Lot of rusty hematite laden water from the loop.

More troubling the flow rate was terrible. maybe 1-2 gallons a minute.

I added a tube of Fernox cleaner to the system and let it run a week.

Returned a week later and very little change.

The loop gets some flow w/ a 0015 on high speed.

Next step is to either pull out tubing or try to flush out junk w/ a flush cart.

Pix to follow.

kcopp

pix.. town/municipal water. Munchkin boiler. A couple Baseboard loops and an air handler.

EdTheHeaterMan

Interesting. That would not be the first time a company kept the manufacturer's rep from knowing all the details.

hot_rod

My understanding was the inner, black full size pex tube is their barrier HePex? The aluminum and PE layer over it was to make it "form stable" that is where the name comes from FostaPex.

The Viega June 2013 Tech Bulletin addresses the splitting outer jacket and they say the oxygen permeation is not compromised by the splitting outer jacket. Maybe find the TB at their website.

Is that what you are seeing the outer grey PE and aluminum splitting?

Has the system been taking on water. Any other place O2 could be entering?

GroundUp

Fosta is everywhere around here, everybody used it for a long time. I also recently had a no-heat call that ended up being a plugged heat exchanger, the whole system was full of sediment. Almost like a coarse sand though, so I determined that it was just poor quality well water used to fill the system along with possibly rust particles from the old mild steel wood boiler that used to be in the loop. I really don't feel like it had anything to do with the Fosta. I have been under the impression that it is their standard non-barrier tubing with the barrier in the jacket but the only potential ingress points would be at the joints so it seems unlikely that they'd have pulled it from the market due to that rather than simply switching it over to their barrier tubing for heating applications…. With that said, I have never once seen a system with non-barrier PEX get sludged up without excessive makeup water. I often cut into NB systems 20+ years old that still look brand new inside, so until someone can show me otherwise, I'm going to stick with my theory that the whole ingress through non-barrier PEX thing is bogus.

kcopp

None, zip, zero of the aluminum is compromised. Its all intact.

The only steel/ ferrous parts of the system that I can see are the circ pumps and the steel manifolds the circ pumps are attached to. Everything else is either copper/ brass or stainless.

Piping to the Indirect and Air handler are in copper.

Makeup water is not an issue. Closed loops. Not leaking HX.

No glycol from what I can tell.

hot_rod

If the aluminum barrier tube intact they it should be O2 tight, more so than regular EVOH barrier Pex.

the DIN standard 4726 on barrier Pex is about limiting the amount of O2 that can enter the tube, not stopping it completely. So the EVOH barrier on pex tube, plastic milk jugs, etc is just to limit O2 to 1G/m3 /day

Mr Pex, the ho brought Wirsbo to the U.S. was very adamant that non barrier tube would cause massive corrosion issues in hydronic systems, the early non barrier rubber sure proved that out.

Aluminum should be a 100% O2 barrier, just as copper and steel tubes.

That being said, plenty of the Watts Onix rubber tube with the aluminum barrier corroded systems.

Hard to believe enough O2 can enter at the end of the tube/ fitting connection? But??

Temperature had a lot to do with O2 ingress. The high temperature fin tubes would pin hole expansion tanks within a year on some rubber tube systems

To me the biggest unknown with aluminum barrier in the middle of the tube is the integrity of that layer. How is that inspected for quality control?

PAP was made with either a butt weld aluminum layer, or an overlap seam, I recall the adhered lap seam brands being the most failure prone.

kcopp

So then what is causing the system to be blocked up w/ all this junk?

If it is a closed system, decent system water and no glycol what could this be? I have seen this to a lesser extent on a small section of 1/2 fostapex a few years back. It has blocked the connection to an expansion tank. This caused the relief valve to blow,

hot_rod

If you get any flow at all, then a power purge should clear the heavy sediment out. You need at least 5 fps velocity to move heavy sludge, the faster the better.

I'm not sure the tube size 3/5??

go here and input tube diameter, and length, then keep upping the gpm till you see 5 fps. That is the flow you need from something.

https://plasticpipecalculator.com/PressureDropHeadLoss.aspx

In a 1/2 loop 250', to get 5 fps the head gets way up there example. 3 gpm= 74' head, probably beyond your flush cart

What was the failure on the 15-58?

I would flush it as best as possible, add good water and keep a hydronic conditioner in the fluid. It's about all you can do at this point. Keep SWT temperature as low as possible.

It was marketed as superior to EVOH type barrier tube, with the aluminum layer.

kcopp

This is from Face book

Hydronic Heating Techs

John Falconi

February 14 ·No heat call, 1st floor air handler coil only getting about 1/3 hot, rest of coil surface ice cold. This is what we found in the old coil when we replaced it and cut it open. Welcome to Magnetite! Viessman oil boiler, hydro-air system all piped with Viega Fostapex I’d say the oxygen barrier is non existent on this Pex! Replaced the coil, re-piped the zone in copper and installed a Caleffi magnetic filter for that zone. Advised the customer he better think about replacing all… See more

GroundUp

Is it possible that the system used to contain more ferrous equipment like CI rads or boiler? Is it possible that when the system was filled, that the water quality was different than it is now? Did you actually test the water quality? I'm not saying it's not possible that this is O2 ingress through the Fosta, but based on my personal experience and never having heard this before (aside from guessing like this and the guy on FB), I would call it very unlikely.

pedmec

I never dealt with fosta pex but what if you tried to do a descaling solution with the pump. Would that work. i'm just throwing stuff out there to try and clean it. i mean it's trashed anyway. Barely any flow. maybe do an hour and see if it helps. if its a bad idea so be it. i got nothing else lol

kcopp

The water is the same now as it was in 2009. Municipal water. That is when the Addition went on.

Never had any CI radiators.

The only steel / CI are the two manifolds and each of the 5 circ pumps. Boiler and piping are stainless and copper…except for the 2 Fostapex zones.

I have used Webb pure pro cleaner in the system for a week. Didnt help after 1 week.

I will need to talk w/ the homeowner about a power flush

hot_rod

knowing all this,

Isolating the tube with a hx

Or all non ferrous components

Or an ingoing chemical romance