PEX Makes It Possible

All modern RVs are equipped with PEX (cross-linked polyethylene) plumbing, like that found in many stationary homes. The pipe itself is super easy to work with and is almost indestructible. It comes in various diameters and colors, but in RV land, ½-inch-diameter is the most common size, with blue for cold water and red for hot. Some still use plain white and some RVs will, rarely, mix sizes for specialty applications.

Unlike metal and old-school PB (grey polybutylene) pipe, PEX is flexible and can stretch, making the material impervious to freezing. The fittings, not so much, but should the system suffer a hard freeze, at least the pipe itself should be okay.

PEX parts manufacturers offer a couple of grades of connectors — and this is where the weakness in the system can be found, sending a clear message as to why water-pressure regulation is so important. Most RVs are equipped with plastic PEX connectors that are crimped in place using ratcheting rings or crimped brass rings. If the connection is under too much stress from movement or freezing, it can break; high water pressure can exacerbate this problem.

Most connectors sourced at a local home center are made of brass, held in place using the same type of rings or crimps. In either case, repair requires the purchase of a specialized tool, which is expensive, but there are new options.

The freshwater system will include a holding tank made of polyethylene, either inside the RV or underneath it. Appropriate fittings are spin-welded into place for fill ports, pick-up tubes, vents and sensors. A drain is also included as part of the system; on some RVs it’s a 1 ½-inch pipe with quarter-turn or slide valve, but most RVs only have a ½-inch pipe with valve or cap under the rig.

PEX plumbing is really easy to repair and maintain, and with the use of push-on fittings, all that is really needed to make repairs and modifications is a pipe cutter and a selection of parts. Because things oftentimes break when least expected, it’s recommended that you keep some plumbing repair parts in your RV tool kit. The most common problems can be traced to unions, tees, loose connector fittings and missing or deformed PEX fitting cone-gaskets. Your local home center or RV service facility will likely have a selection of ½-inch parts. As mentioned earlier, there is a better option for repairs and mods. Push-on fittings are available on Amazon including, for example, a female swivel elbow (https://amzn.to/3tyygED) that can make replacing a fitting a 5-minute job. If it’s just a bad cone washer, you can get a 10-pack (https://amzn.to/3euIS2X) to keep in the toolbox for a quick swap out.