A funny thing happened on the way to writing my last article on plastic pipe and venting. In researching the topic, I learned a lot more about thermoplastic piping in general. Although not an expert by any means, I uncovered some interesting information about plastic pipe past, present and future. Because of the venting article, some may surmise that I dont like plastic pipe. Nothing could be further from the truth. I am a big fan of plastics for a number of reasons, and believe that when properly utilized in a hydronic system, plastic is almost always superior to metallic piping systems. A quick look at the past shows that in the vast majority of installed hydronic systems, thermoplastic material is performing flawlessly. The only failures of note are products that were not manufactured according to material specifications or products that were misapplied. One big disappointment for me was when Polybutylene (Poly B) pipe was blamed for massive failures that, in reality, just did not happen. I really liked Poly B pipe. There were isolated failures of pipe, improperly used, in domestic hot water recirculation lines where high continuous flow velocities or high chlorine levels caused deterioration. There were widespread fitting failures, which had nothing to do with the pipe, and there were isolated failures due to excessive heating of Poly B in Southern U.S. attic spaces. There have been widespread problems with oxygen diffusion through Poly B and PEX tubing without oxygen barriers, but you cant blame the pipe it was the failure of designers and installers to understand that oxygen diffusion could be a problem. Simple precautions could have prevented most of the issues. Once the ambulance chasers were finished with their class action lawsuits however, the product was withdrawn from the North American market and is not likely to be seen again, even though it is still used extensively in other parts of the world.
The material of choice
Presently, cross-linked polyethylene PEX is the material of choice for radiant heating and plumbing systems. Properly applied, it performs without a hitch. The hybrid PEX Al PEX tubing (aluminum tubing sandwiched between an inner and outer layer of PEX) is the favourite of many hydronics and plumbing professionals. The biggest issue with both of these materials however, is that they are not very popular in larger sizes. We tend to use them for radiant panel tubing and smaller diameter (1 1/2 and less) distribution piping, but not for mains piping. There is some use of PVC and CPVC piping in hydronic and plumbing systems, but their toxicity in fire situations and their high thermal expansion rates can create serious installation problems. Polyethylene pipe is widespread in plumbing applications and comes in some pretty mondo sizes, but it doesnt perform well at the higher temperatures common in hydronic systems.
The future?
In researching the venting issue I asked a number of engineering types what their material of choice would be for venting gas appliances. To a person, they all had the same answer polypropylene. What the heck is that and where do I get it? Polypropylene is a highly stable, chemically resistant thermoplastic that has been in widespread use around the world since the early 1980s. It is used for appliance venting, potable water distribution, hydronic and chilled water distribution, chemical and compressed air piping, foodstuff (like milk) conveyance, and on and on. When I first heard about it I thought, why havent we seen this stuff here in North America? It sounds like a wonder pipe. I still dont have an answer to that question, but it is starting to appear in the plumbing and hydronic industries here. One of the first people here in Calgary to use it extensively is Frank Scobie of Tosco Mechanical. Reeling from the recent increases in copper pipe and fittings, Frank did a little searching and found a German company called Aquatherm that was looking for contractors to adopt their polypropylene pipe for use in plumbing and hydronic heating distribution piping systems. Frank got together with Don Nagle from Emco Limited a distributor of this product and they started to run the numbers. Not only was it less expensive than using metallic piping, the more he looked into it, the more Frank became convinced it was a better choice all around for other reasons. Under normal operating conditions, this stuff is chemically inert, corrosion proof, non-toxic in case of fire, quiet, and retains heat (less pipe insulation needed). It is easy to install, hangs straight, and looks good. The fittings look very familiar, socket fusion tees, ball valves, elbows and other fittings look like their metallic counterparts. Contractors like ABS pipe because it is easy to assemble by gluing. ABS is highly reactive to a number of chemicals, which means that solvent cement will make short work of it. Unfortunately so will other chemicals. ABS has proven to be a real champ when it comes to DWV applications no real problems, but caution is the order of the day when using it where it may come in contact with high temperatures and reactive chemicals. Polypropylene is so resistant to chemicals that the only practical way to join it is through fusion welding. I have to admit bias here, I have always been a big fan of fusion welding (I used to have a ticket for fusing polyethylene gas piping). Properly executed, a fusion weld turns two pieces of pipe into one full stop. No chance of joint failure period.
The down side
What you might well ask is the down side of this stuff? As far as I can see, there isnt much going against it. The fusion tools are expensive if you are starting from scratch, but if you use a lot of this pipe, you should pay that investment off in a few jobs. Your installers have to be trained to do the fusion welds properly, but once you are set up, it is really no more complicated than doing a proper glue joint on a CPVC fitting. I would like to see some sort of trade ticket for the fusion welding process to ensure consistent quality, and I think the industry has to be extremely diligent that the quality of the material is maintained at the highest level. Aquatherm is a German company with diligent engineering and quality control practices that has obtained all applicable approvals on their products (including fire-stopping) for use in Canada. We must stand guard however, against some of the inevitable bad quality knock-offs that will be coming at us. My experience with plastics over the years is that a momentary lapse of quality control and testing can have disastrous results down the road. Not putting in the correct formulation of stabilizers, for example, can result in catastrophic product failure. To prevent this from happening, the industry must make manufacturers adhere to the highest standards and see that their products are rigorously and regularly tested to make sure that everything that gets installed in this country meets the required specifications. The only thing I wonder about all of this is& what the heck do they have coming at us next?
Roy Collver operates Mechanical Systems 2000 in Calgary and Edmonton. He can be reached at royc@ms-2000.com.
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