PART #3 OF 8
HOW MUCH PRESSURE?
Prior to roughly 2000 many RVs used gray color polybutylene pipe, but it proved vulnerable to chlorine disinfectant in tap water. Since then the great majority of modern RVs now use durable PEX polyethylene piping, typically white, red or blue in color with a minimum 30 year lifespan and decent expansion to resist freezing damage. PEX is rated to 160 psi at 73 F (room temp) and 100 psi at 180 F (hot water). The actual burst point is closer to 400 psi for PEX in new condition. Since most pumps operate in the 30 to 55 psi range, your PEX plumbing is designed to withstand at least TWICE the pump pressure, a decent safety margin. Moving from a 45 psi OEM pump to a 55 psi aftermarket pump, for example, should generally not cause leaks or other problems, and is commonly done. Experts nonetheless suggest limiting pump pressure to 60 psi or less unless you have a need to go higher. The water fixtures in your RV have pressure limits as well, so it's not just about the pipe and fittings.
PUMP AMPERAGE
Flow (gpm) is more important than pressure (psi) for most RVs, especially with multiple water fixtures in simultaneous use. But pump amperage draw is largely dictated by flow. So going big on a pump flow rating can potentially overtax your pump's electrical circuit, and there's no need for a little teardrop trailer to have a 7 gpm mega-pump. As an example, Everflo pump max gpm/max amps draw for six of their pump models: 1.0 gpm/4.0 max amps, 2.2/8.0, 3.0/10.0, 4.0/13.0, 5.5/17.0, 7.0/23.0. (Their 3 gpm pump uses a max 10 amps, for example.) Notice how with these pumps if you double the flow (first number), you almost double the amperage (second number). I believe that many RVs come with 10 amp pump fuses/circuits, so you can see how going much above 3 gpm starts to become problematic. Therefore you might limit your choice of pump gpm to only what’s needed. And Flojet suggests 3 gpm equals three RV water fixtures in simultaneous use, and how many people exceed that? Note that other pump brands can have very different numbers than those above.
