Leaking water pump, but not what you think...

[A.Texas.Yankee]

Long story short, we've had small puddles behind the wet bay that we just recently discovered which led me to discover junk installation of junk fittings. Not sure how long it's been leaking, but very little signs of widespread damage. Off to the dealer to have them document and drop under belly for some inspection and warranty work.

So, I had replaced nearly all the plastic fittings that were leaking, which was almost 9 fittings. Yes, 9. All with light leaks. 3 days later of replacing fittings and testing I was pretty sure I'd replaced all the bad fittings but... Leak detector wakes me up around 3 AM. Sure enough there's a significant slow leak. Where I couldn't tell. Small leak but there. I sat there for over an hour watching, could not locate leak. No dripping of any kind. I get cold, bored, shut off water, and head inside to bed.

Had to work so I had to wait until next evening to diagnose. Turn water back on and sit there... for almost two hours, no leak. I'm confused. So I head inside grab a remote camera (part of my Wyze set up) and get it set up. I'm watching this screen for hours off and on, nothing. I take a shower and then check the screen. A puddle!!! I'm watching the screen, no dripping. Puddle doesn't increase in size. I head back out, watching, inspecting... no wet fittings or hoses or anything. Just a puddle! So it's late and I'm frustrated beyond belief so I shut off water for the night and head inside. Minutes later the leak detector is going off. Sure enough puddle is bigger, dripping even, and right from the water pump... but there's no water pressure. City water is off, pump is off, but there's residual pressure in lines. So I turn back on City water... leak stops. I'm flabbergasted. Turn city water off, pump starts dripping!

TL&DR:

My water pump only leaks when no pressure is applied to the lines and leaks until the water in the line empties. WTH is going on here?

Full Timing Family
2021 Momentum 395MS-R
2021 Ford F450 King Ranch

[FT4NOW]

Where on the pump is it leaking?
Does it leak if using the water pump?

My initial thought is there is a crack somewhere on the pump, and when the lines are pressurized with city water, the pressure keeps the pump's check valve shut. When pressure in the line decreases, the check valve doesnt necessarily stay shut and allows some water flow which leaks out through a possible crack in the pump.

Sent from my SM-G950U using Tapatalk

[A.Texas.Yankee]

Where on the pump is it leaking?
Does it leak if using the water pump?

My initial thought is there is a crack somewhere on the pump, and when the lines are pressurized with city water, the pressure keeps the pump's check valve shut. When pressure in the line decreases, the check valve doesnt necessarily stay shut and allows some water flow which leaks out through a possible crack in the pump.

Sent from my SM-G950U using Tapatalk

Does not leak when using pump as long as it's pressurized. It's leaking from the housing, near the impeller, but because of where it's mounted I can't get to that side. I'll have to disconnect a few lines and remove the pump to inspect.

Full Timing Family
2021 Momentum 395MS-R
2021 Ford F450 King Ranch

[Gronk1]

Check the filter going into the pump. I had a similar leak to yours & it was the housing had a hairline crack. It must have been put on by the Hulk-took a lot to get it off. I now carry an extra.

[Just Krusen]

After 2 water pump leaks I added ball valves on both sides of the pump. Now I can remove the pump without shutting the water off to the rest of the trailer. I also bleed off the pressure after using the pump and close the valves. Both bad pumps had leaks. One leaked internally and the other had a housing leak.