Polybutylene strikes again

Jack, CVMS

I changed out a Grundfos pump on a baseboard hydronic system. It didn't occur to me until the next day what I was looking at there - the whole house is plumbed with QEST PB tubing. A Burnham boiler, UP15-42F pump, etc.

The fluid looked like it was 20 years old, although I know the house isn't that old. The Extrol tank was replaced once, not too long ago, the pump bearings were binding. And I realized that there are a lot of homes with hydronic heat done with PB in the area. They all have one thing in common - problems with leaks and pumps. So it looks like it is time for me to start informing home owners that things are only going to get worse. We'll be putting a SS HX on the system where I just changed the pump, and flushing everything, then putting in new fluid. Then a new bronze pump and expansion tank on the baseboard side. All the money they saved using PB when the house was built will be used up in the retrofit.

Any advice from you guys who may have done this before is welcome. The only time I've installed HX's in the past was for DHW. Looks like I'll be putting in some whole-house exchangers soon.

Ken_8

PB?

The problem is not the material - but the designer.
No O2 barrier?

Must have non-ferrous HX and/or SS boiler and brass pump.



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kevin coppinger_4

another thought.....

would to use an aggressive systemwide chemical treatment... although the hx will be better in the long run.kpc

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hr

Two choices

seperate the pb with all non ferrous components, or an O2 scavanger. Remember the HX seperation will not stop O2 ingress. Other materials are prone to corrosion

The chemical route would be, by far, the least expensive. Clean the system well and add O2 scavangers. It's really not hard to treat a system. It will protect pumps, boilers, and all the components.

Generally a check up every two years and maybe a boost additive. No need to start over.

Consider it's gone this long without any treatment

Here is a MSDS sheet from a inhibitor that some of the outdoor wood furnace folks include with purchases. It's a fairly simple fluid, mainly O2 scavangers. Made for hard water steam boiler treatment.

Be sure to use a dependable backflow preventor. Some areas now require RPZ type, arounde here. Cheap insurance if you connect to potable sources. Label the system as to what is inside!

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Floyd_5

Did one this past summer...

The guy called and complained that his extrol tank had failed...again, the third one in ten years. Install a FPHX and bronze pump with a potable water expansion tank with the air backed down. Also turned the temp. down on the water to 160 and he made out okay till the temps. started hovering in the single digitd... explained to him that he could crank the temps up tempporarily and that he should back them dowm once it warmed up outside to try to save the PB as long as possible. Also there are some theory's out there that fell that the O2 deal isn't quite as bad at lower temps.
I also made the homeowner aware that he is sitting on a time bomb and that at somepoint in time the PB will have to be replaced and that he may want to seek other alternatives for heating at that time.
I suggested RFH, either plates or Quik Trak.....no matter what it will be a real mess.... this home is a very beautiful home and it will be a shame to rip it up.....

So far everyones happy......

hr

I'm not sure the PB

itself is going to fail. It's still used quite a bit in other countries. Vanguard still extrudes it, I believe, and the Thawpack snowmelt systems for carwashes still spec PB, at least a few years back I bid against a PB system sold through carwash equipment channels.

Typically snowmelts run real low temperatures with inhibited glycol. Plenty of those around here close to 20 years old.

The fittings and rings, as well as the chlorine levels doomed the PB. My earliest radiant jobs were pb, dating back to the mid eighties. So far all are still running, although at exp tank costs, etc, until we found Elvis:)

Now that the causes are known (we should have listened to the "across the pond" guys) handling the exisiting systems should not be a problem.

Also some of the PB out there was O2 barriered, look for the shinney EVOH coating. Infloor was one brand available with the barrier. PB was a thin walled tube, easy to handle and install, but I like the SDR9 pex better, for addition wall thickness and protection from the arbitrary

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Floyd_5

I hope I'm wrong.....

and the PB gives them many years now......would rather set them up for the possible failure than, assure them that everything's honkey dory and then have it blow up in my
face. :-)

So is chlorine the "bad guy" with PB???? I thought heat was a factor also... made it brittle?? Or was that an "old wives tale"???

Still learnin' in Pa.

Floyd

Jack, CVMS

O2 Scavengers

So this chemical will reduce or eliminate the effects of the oxygen in the system on the ferrous components? That definitely sounds like the simpler solution, even if it does require periodic replenishment. The temperature loss through the HX was a concern I had, as it looked like I would have to run the boiler temperature up to around 220° or so to get hot enough water through the baseboard to take care of cold weather temperatures.

Just about every system up here uses a propylene glycol mix, and most of ours don't even have make-up water. If the pressure drops off significantly we find the leak, fix it, and pump more fluid in.

Jack, CVMS

PB longevity

Back in '81 I installed some PB on a co-gen system (many people out of town here still have to generate their own electrical power with diesel-powered gensets) using the excess heat to help heat the house. After 20 years or so we dug the 3/4" line up to replace it with 1" for greater flow. The line was still in fine shape after all those years with ~160° water/glycol mix 24/7. The coolant is another matter, although at the lower temperatures (than a boiler) it hasn't deteriorated too badly. Wish I'd been aware of the oxygen permeability issue back when this was originally installed - would have used soft copper instead.

Ken_8

It is not quite that simple

The 02 treatment/inhibitor has limited life.

Ever heard of someone testing and flushing the system annually to assure the 02 protection is still "active"?

Every year?

Without fail?

Because if you don't do that - you can kiss the entire system goodbye.



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John MacGregor_3

PB pipe

We have used PB pipe quite extensively in the past, including here in the shop for both plumbing and heating. After 15 years it's percing right along with no problems at all. I put it in my cabin in the UP that was on cedar blocks and kept shifting and settling and every deer season I had to take a length of copper, a pound of solder and a tub of flux and an extra day to fix the leaks. PB ended that problem. We have used it on snowmelt, infloor heat, plumbing, including our first pb job, which was an underground house. We were concerned about the plastic fittings, which was all that was available at the time, so we ran it all in 3" pvc sleeves, fixture to fixture. We had one leak on an elbow and switched to brass fittings for the rest of the time we used poly.
The only place we ever had problems was when we tried to use it for hot water circulating lines. It will not hold up to constant high temperature. The only other problem is it will be attacked by chlorine. That is what happened in Houston TX with their $10mill. lawsuit over the failed mains,services and in-house piping.

Duncan_9

Lower temperatures

"Also there are some theory's out there that fell that the O2 deal isn't quite as bad at lower temps"

Not theories, Floyd, it's a fact.

hr

It can be simple

I have a very inexpensive test kit that test the inhibitor levels. It requires a draining of less than a cup of fluid. It is similar to a pool test kit. If the fluid is weak you need only add a pint or so of "inhibitor boost" chemical.

No need to flush and start over, really. If, or when, your pool chemicals fall low you don't drain and refill the pool do you?

Not all systems need attention yearly. The depletion of the O2 scavanger is directly related to the O2 ingress. Keep the temperature low and the corrosion problems are very minor.

Same with the chemical treatment program. It's an option to a repiping and HX seperation to be considered, not the ONLY way to handle corrosion issues.

Corrosion only occurs when O2 is present! Address the O2 and you don't have problems.

Ever see corossion problems in a copper piped iron boiler? Unless the system takes on make up water they drain and look the same 20 years later, generally. It's the use of plastics, regardless of the type and brand that have brought on this whole issue, in my opinon O2 barriers are not 100%, like insulation they slow down the ingress rate, can't stop it 100%. I believe.


Keep in mind the corrosion inhibitors chemicals have other ingrediants to protect your system. PH buffers, hardness lock up components for "messy fill water" film providers to protect pourous casting, etc.

It's the mix of multi metals in todays modern boilers that really add importance to treatments. Aluminum and stainless steel bring some challanges to hydronic systems. MZ, Weil Ultras, and other Aluminum block boilers either come with an inhibitor, or suggest brands to use. Time will tell how the materials hold up in the long run. A little attention to water quality goes a long way to protection those high dollar, high efficiency HXers.

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hr

Floyd

not chlorine specifically, but elevated levels of it. What ever an elevated level is Seems certain water suppliers really juice up the chlorine levels at times, either by operator error, or to handle a problem. That is when the PB gets attacked, according to the folks that will talk about it! Generally not the sales folks

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