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Old 10-01-2016, 08:46 AM   #29
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I think this topic is the result of the historical range of quality of construction for RV's, with little or no regulatory requirements. Some of those older RV's might have struggled at 40 psi. But most of today's RV's, and certainly the better brands/models, have pressure ratings comparable to houses. I have no problem setting my high flow pressure regulator at about 50-55 psi. One still has to protect against campgrounds that compensate for their poor plumbing by raising the supply pressure.
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Old 10-01-2016, 04:39 PM   #30
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I think it pretty safe to say the system's pressure at that point is well in excess of 100psi?
A risky assumption, I think. The water heater manufacturer puts in a PT valve to avoid heater explosions. Covers his butt for lawsuits, but he isn't protecting the rest of the RV. RV makers aren't pressure testing anywhere near that high and the RVIA code doesn't require it.

By the way, the plumbing in your house probably isn't rated for 150 psi either. Local codes and practices vary, and standards have changed over time, but most are probably tested at 90 psi or so.
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Old 10-01-2016, 07:02 PM   #31
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Check it out Gary. Look at the pressure required for that valve to start weeping. Many, if not most of us have seen that happening. Why would you engineer/build a system that would not contain that pressure if you were going to use a valve like that anywhere in your system?-Al
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Old 10-02-2016, 12:30 AM   #32
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I asked a Mobile RV Tech this pressure question two weeks ago. Our manual says 40psi max. (perhaps not up to date?) The tubing is PEX and hard pipe reads 80psi. He recommended 60psi on our regulator which he recommends to most everyone. So far all is well set at 50psi.
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Old 10-02-2016, 01:05 AM   #33
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Something worth pondering -

The pop off valve in RV water heaters is designed to release pressure at 150psi (or so). Logically, the coach manf's are not going to want that hot water venting inside a coach due to a ruptured line/fitting, so they had better build the water system to hold to AT LEAST that pressure.

Sound far fetched? How many of us have seen that valve weeping as the water warmed up during the water heater's first cycle? I think it pretty safe to say the system's pressure at that point is well in excess of 100psi?

That thought in mind, 65psi. seems like childs play....
The max pressure rating for Polybutyl (the grey pipe) is 100psi at 180 degrees. PEX (white/blue/red) is higher. They stopped using Polybutyl in mid 1995 due to deterioration of the pipe from chlorine.

Watts recommends regulators for all systems with 75 psi or greater pressure.
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Old 10-02-2016, 01:25 AM   #34
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Originally Posted by Gary RVRoamer View Post
A risky assumption, I think. The water heater manufacturer puts in a PT valve to avoid heater explosions. Covers his butt for lawsuits, but he isn't protecting the rest of the RV. RV makers aren't pressure testing anywhere near that high and the RVIA code doesn't require it.

By the way, the plumbing in your house probably isn't rated for 150 psi either. Local codes and practices vary, and standards have changed over time, but most are probably tested at 90 psi or so.
PEX (Used in RVs after 1995) carries the following hydrostatic temperature and pressure ratings:
  • 200F at 80 psi
  • 180F at 100 psi
  • 120F at 130 psi
  • 73.4F at 160 psi
However, many components in RVs and your home have recommendations for far lower PSI. For example, rubber (not SS jacketed) washing machine hoses, dishwashers, and icemakers. Typically, those are around 80-85 psi MAX.
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Old 10-02-2016, 06:57 AM   #35
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To clarify, my point was regarding the question of whether or not a system could be run at 65psi safely. I'm thinking there isn't much doubt here that 65psi is pretty safe.

Beyond that, I'm amazed they routinely hold at MUCH higher pressure - though I would never run my system anywhere near that high on purpose.
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Old 10-02-2016, 07:31 AM   #36
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To clarify, my point was regarding the question of whether or not a system could be run at 65psi safely. I'm thinking there isn't much doubt here that 65psi is pretty safe.

Beyond that, I'm amazed they routinely hold at MUCH higher pressure - though I would never run my system anywhere near that high on purpose.
Agreed ... primarily I was warning owners of pre-1996 (and maybe a bit later) RVs that their pressure should be set lower than newer RVs. My Endeavor (and maybe yours) had the dreaded Polybutyl. Although my pipe seemed ok, it was getting a few bad joints. Thank goodness it did have copper rings and not the really bad plastic clamps. I still have a bag of Polybutyl to PEX adapters ... what fun!
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