High city water pressure causes drain hose leakage behind rear bath tanks.

[bdhdig]

Our '77 31' rear bath has 2 drain tubes through the belly pan near its bumper. The road side (left) one is hot and cold water and the other is the one that drains/drips when city water pressure is too high. The hot/cold has accessable operable valves. Recently, the second drain tube has been dripping with only the pump pressure (about 45 psi). Is there an explanation to this situation? What/where could be the source of this hose so I can fix the cause for leakage? The attached photo of the "basic water distribution system" from its service manual doesn't give any clue, imo. We've owned this coach since '88.
Thank you in advance.

[4RXLA]

I have a ‘77 rear bath 31’ also and once in a while I get a small drip from that location. Usually the leak occurs after the trailer has been in storage for an extended period. I attribute the drip to 45 year old valves. I open both while under pressure and after a day or so the drip stops, presumably due to the seal in the valve expanding and seating.

[bdhdig]

Thank you for your response and I agree with your scenario. However, I successfully rebuilt both hot and cold valves, which both drain through the left tube. The mystery remains to be the tube on the right, where/what it attaches to allowing the leakage.

[4RXLA]

You are right that both valves drain through 1 tube. I’ve never had dripping from the other tube. As you know there’s alot of plumbing in that area. Perhaps it is some type of pressure relief mechanism that is malfunctioning. Do you have 2 fresh water inlets or just the one next to the sewer outlet?

[bdhdig]

As the photos show, there is only the single water connection and the pressure is now regulated at a reasonable rate. Your thought of the onboard pressure regulator malfunction may be what to consider. When we return to our home base, I will attempt to remove and disassemble that regulator. At this point, I can't think of any other cause. Thank you for suggesting a possible solution direction. We'll see.

[Mollysdad]

Originally Posted by bdhdig

As the photos show, there is only the single water connection and the pressure is now regulated at a reasonable rate. Your thought of the onboard pressure regulator malfunction may be what to consider.

If the water pressure is controlled at the hose bib, then regardless of the onboard regulator, I don't see why it would cause a leak. It doesn't stop the flow of water, working or not. What am I missing?
Is it possible the right spigot is the fresh water tank drain?
Also the diagram shows a drain for the water heater too.

[4RXLA]

I’ve always used a regulator at the spigot and don’t rely on the built in regulator. The Excella 500 has a 2nd fresh water inlet next to the 30 amp cord-both on retractable reels behind the wheel well. There must be something built in to the plumbing that closes off the inlet not in use.

[waninae39]

i added an adjustable water pressure meter inside close to the ext outlet to prevent over ly high water pressure

[bdhdig]

"Perhaps it is some type of pressure relief mechanism that is malfunctioning."

Had to look deeper into the valve and pressure regulator area in the trunk to find this (1/2" inlet/outlet) 60 psi PRESSURE RELIEF VALVE located between the city water connect and the cold water drain valve. After removal, I tried compressed air to blow out any foreign matter from seat, but still dripped.
So far, I've only found a 75 psi valve possibility on Amazon. Would 75 be a safe psi for replacement? Do other Airstream coaches (or sob) have this factory installed pressure valve?

[4RXLA]

Originally Posted by bdhdig

"Perhaps it is some type of pressure relief mechanism that is malfunctioning."



Had to look deeper into the valve and pressure regulator area in the trunk to find this (1/2" inlet/outlet) 60 psi PRESSURE RELIEF VALVE located between the city water connect and the cold water drain valve. After removal, I tried compressed air to blow out any foreign matter from seat, but still dripped.

So far, I've only found a 75 psi valve possibility on Amazon. Would 75 be a safe psi for replacement? Do other Airstream coaches (or sob) have this factory installed pressure valve?

my ‘77 has this and I still have the factory copper plumbing throughout.