Flushing and cleaning polybutylene hydronic snow melt system

MatthewPK

I recently bought a house that was built in the early 90's with a hydronic snow melt system. It uses polybutylene pipe embedded in the driveway concrete.

There are no leaks and things work ok but I want to replace the boiler and I am pretty sure the glycol has never been replaced since initial install.

I feel confident that I can replace the boiler and flush the system but I want to be especially gentle with the PB piping. I feel like I should flush it with cleaning solution, too, given how long it sat and ran with old glycol.

I've read data sheets of multiple products for hydronic system cleaning but none specifically mention that they are safe for PB. I don't mind contacting manufacturers, but I suspect that none of them will be willing to say their product is ok to use in PB either.

Does anybody have any recommendations? Am I overthinking this?

Thanks in advance!

Mad Dog_2

I don't think you're overthinking it at all!  As far as I know, PB is NOT commonly used for Snowmelt, radiant or anything other than underground lawn sprinklers.   Its soft, thin and I'd love to see the joint construction.  Anywho, I would gather info from a Company like Rhomar, the glycol company,  AND the PB make. If needed a quick friendly call to a chemical engineer could confirm it.  My great Father In Law Don, 
Holds a Chemistry degree PLUS knows construction for 70 years and always amazed me with his innate knowledge of things like that...
"You can't put Poly-whatever in that soil, its too acidic and blah blah blah.'  Thats what I would do buddy.  Keep us posted.  Mad Dog 🐕 

kcopp

You are probably better off using a heat exchanger w/ the new boiler. Some sort of shell in tube to isolate the boiler from the tubing regardless of the tubing. IMO the less glycol in a boiler the better.
PolyB got a bad rap IMO. I installed a ton of it for the company I was an apprentice for. No issues. The aluminum crimp rings w/ the acetal fittings were the real issue and if a city has very high chlorine water in it the tubing didnt do great.
I saw a number of homes that has frozen pipes and not one split. inch per inch it is actually stronger than pex.

hot_rod

Really the only downside to PB is that it doesn’t have an oxygen barrier. It worked well as a radiant tube.

Isolate it with a HX is a good idea. Any of the hydronic cleaners would work to flush any sludge.

Mad Dog_2

The first large snowmelt system I did in 2003, I regret not installing a Flat Plate HX, but it was done on a shoe string budget.  Everything working great the first season, until one of the main pumps went down and I got some air out in the loop field.  If I had installed the HX, I only would have had to contend w air on the boiler side of the HX...easy!  Not too big of a deal as far as safety, but with Snowmelt, if you have an area with strips of snow, you're in the doghouse. Spent many hours purging it out at the manifold boxes in 5 degree weather.  I love the cold, but my frozen hands were complaining 🙃 alot!  The other mistake I made was NOT putting a Spirovent in. To keep cost down, Someone suggested another brand, but it didn't cut the mustard. Wound up cutting it out a few seasons later.  Yup HXers are your friend like extra valves, purge tees, and clean outs on drainage are. Mad Dog

MatthewPK

I don't understand the recommendation to use an HX here. Can you explain some of the reasons?

Right now I have a single zone, single pump system which runs glycol through the boiler. To use an HX I would need two loops, two pumps. I would circulate water through the boiler but what else do I gain?

hot_rod

That PB tube does not have an oxygen barrier. As such O2 constantly enters the system, which breaks down the glycol inhibitors
When the inhibitors break down sludge forms from the corrosion of ferrous components

A heat exchanger allows you to seperate the 
PB from the boiler and ferrous metals

Or pipe the boiler with all copper, brass, stainless. Including circulators and expansion tank

MatthewPK

Makes perfect sense. Thanks!

Will oxygen enter the system through the tubes embedded in the concrete?

hot_rod

MatthewPK said:

Makes perfect sense. Thanks!

Will oxygen enter the system through the tubes embedded in the concrete?

Yes, concrete is not an oxygen barrier

Mad Dog_2

Listen Carefully. HR knows...take it to the bank!!!!  Mad Dog

JUGHNE

I have a couple 1000 feet of PBOX in my house buried in concrete and walls.

It is O2 barrier, red in color, 3/8" ID and installed in 1995 or so.

Made by Infloor Heating systems. No problems.

The first CI boiler and a fair amount of black piping looked good after 15 years, now ModCon boiler.

hot_rod

I think InFloor was one of only a few that made oxygen barrier PB, for a few years. It should be as good as oxygen barrier Pex.

Oxygen barriers do not stop 100% of the ingress and it is atemperation. Relationship. The hotter the temperature the higher the amount of O2 that can enter.

The DIN standard on the tube defines the allowable amount of ingress

PE tube with the welded aluminum layer PAP, do the best job of
slowing ingress.

JUGHNE

Hot Rod, how does this rate in your opinion? 120 degrees operation.

kcopp

I still see hot water baseboard systems out in the field that are piped in PolyB. They still work although I have had to flush the snot out of them w/ cleaner and add inhibitor.

hot_rod

JUGHNE said:

Hot Rod, how does this rate in your opinion? 120 degrees operation.

I thought it was an excellent radiant tube, better at heat transfer with a thinner wall compared to Pex. It could be crimped, compression fitting, or heat fusion to melt together the fitting.

There were some DIN standards for the EVOH oxygen barrier on the radiant PB.
If you can see several feet of the tube it might have DIN 16968, 16837, or 4728 printed on it.

Pex will have this standard for oxygen diffusion. I don’t know what that milligram per liters amount is? It goes up with temperature.

JUGHNE

ASTMD-3309 SE PB 2110 SDR-11 .062

Do you see anything in all of this?

kcopp

The problem now is finding fittings to use on it.
You would need to do some web searching...
Mybe a Canadian supplier would have them.

JUGHNE

I had one of these manifolds with leaking connections. They were simply push in and thus locked in place.
Also the balancing valves were frozen in place.

A new manifold for pex connections was used. Transition was done with a push in type coupling.
No problems so far after 5 years of change out of manifold......15 PSI only applied.

hot_rod

JUGHNE said:

ASTMD-3309 SE PB 2110 SDR-11 .062 Do you see anything in all of this?

I don’t recognize any of those as oxygen standards. Lance at PPI might

Infloor started in the mid 1980s. I think they were tied with Hamel industries the gypcrete folks at one point?

Sometime in the 2000s I believe the Wilburn family bought the rights somehow. They still have Infloor running in Buena Vista, Colorado

Some of the PB extruded in Europe had listed those DIN standard for oxygen designation. There was a company out of Holland that extruded o2 barrier pb, a 5 layer tube

The shiny coating is the EVOH, it usually squeaks when you rub the tube against itself

I think they coat over the EVOH barrier on most Pex tube to protect and quiet it down🤓