Why ABS?
Dear RV Doctor:
Why do RV manufacturers use plumbing made of ABS material instead of PVC?
Paul H.
Toledo, Ohio
Both ABS (acrylonitrile butadiene styrene) and PVC (polyvinyl chloride) material can be used for RV plumbing, but ABS drainpipes are preferred because they have a broader temperature range, from 40 degrees below to 180 degrees above 0 Fahrenheit. Simply put, ABS material does not lose its impact resistance at extreme temperatures. PVC pipe has a recommended operating range of 32 degrees to 92 degrees. With PVC, a dramatic decrease in impact strength occurs as the temperature gets colder, meaning PVC becomes more brittle the colder it is. As an example, PVC’s impact strength is four times less at 22 degrees than it is at 52 degrees. This means that at low temperatures, the ability of PVC to dissipate energy from a sudden blow (or a sudden racking of the RV as it travels) is limited and may result in a failure. I’m sure cost is a factor as well. I’m not privy to the wholesale prices that RV manufacturers pay for the different types of pipe, but I would guess that ABS piping and associated fittings are less expensive overall. By the way, both ABS and PVC are considered thermoplastics, meaning both can be hot-air welded as well as cemented.
More ABS
Dear RV Doctor:
Our macerator pump fitting with the four little grabber hooks is glued either into or onto the pump. One of the little hooks broke, and the fitting leaks a drip or two a minute. Our service technician was able to buy a new part, but he cannot separate the glued pipes. The company that manufactured the macerator said that they do not sell the piece he needs to complete the repair and told him we would have to purchase a new pump if he can’t get the ABS glue off the pipes. He is afraid to pull the pipes apart, because he will distort them in doing so. There is not enough room to cut and redo them. Is there some way to get two pieces of black plastic apart? Can you think of any other options?
Jane Nowlin
Navarre, Florida
An experienced RV service technician should be able to separate cemented ABS fittings and recondition the female portion in order for them to be re-cemented. It takes patience and a little expertise. Once the ABS pipe section is cut through, a small hacksaw blade or die grinder with a cutting wheel is used to make two lateral cuts, about 1.5 inches apart, just through the cemented portion of the pipe. Once that 1.5-inch section is pried out with a screwdriver, the remaining portions of the pipe can be pried and curled out of the female portion of the fitting. The fitting then can be sanded and prepped for re-cementing, usually with success. All that said, by code, it is not permissible to reuse plumbing fittings. Oftentimes, however, it is the only option, especially in a confined space. I can’t quite visualize the setup on your particular macerator, but it may simply be a matter of cementing a new bayonet fitting — the piece with the four little nubs — onto an ABS adapter that is threaded into the macerator.
Why EPDM?
Dear RV Doctor:
Is EPDM the only material used for motorhome roofing? Is there a better material available?
John Hubbard
Burton, Michigan
EPDM (ethylene propylene diene monomer) is probably the most common type of motorhome roofing surface these days. But through the years, motorhome roofing options have included aluminum; galvanized steel; ABS; fiberglass; and TPO (thermoplastic polyolefin), another synthetic roofing material. I’ve even seen a wood-shingled roof on a custom coach! There are variants for many of the aforementioned types, such as one-piece, individual panels, sectional, etc. Most modern motorhomes will have either EPDM, TPO (of which there are two different types), or fiberglass. Which is best? Well, that’s a subjective question. Each has its pluses and minuses, including cost, weight, wear and tear, maintenance, etc., and reasonable arguments could be made for and against each type of material. But the type of roofing material used would not be high on my list of deal-makers or deal-breakers if I were purchasing a new motorhome, since they all require some level of proactive maintenance and care.
Motorhome Inclination
Dear RV Doctor:
My motorhome sits on an approximate 10-degree incline in our driveway. Should the back end be lower for drainage, or does it make a difference?
Frank Clymer
Newark, Delaware
It depends on what you are draining. If you simply want to make sure rainwater does not accumulate on the roof, it makes no matter which end is lower. Any slant usually will allow water to run off the roof. Just be sure the refrigerator is turned off while the coach sits in the driveway, because refrigerators are not meant to operate when too far out of level.
If you’re trying to drain the waste plumbing systems (gray and black holding tanks), then the motorhome should be relatively level, and it certainly should not lean drastically to the passenger side. All waste plumbing fittings and tank outlets are manufactured with an integral internal slope, and all drain piping must slope toward the holding tanks from the drain outlet to the tank inlet. If the coach is radically off level, it’s possible that the drain water could remain in the pipes. This can lead to bacteria growth and sewer odors. Plus, it would make it difficult to properly drain and flush the holding tanks completely if the coach were drastically off level.
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