Community Forums

rlbow43 · 07-26-2015, 02:26 AM

Last week we spent 3 days at a nearby rv park. I only filled the fresh water tank to 50% before we left. The 2nd day I noticed water draining out of the fresh water overflow line. I checked the fresh water gauge. It was at 100%. I checked the water fill valve. It was at Local Supply. What can cause the fresh water tank to fill when the valve is at Local Supply?

Dtwallace · 07-26-2015, 04:44 AM

I don't have a schematic of your water system, but if your water pump is on the pressure side of the city water coming into the coach, it could have a leak back issue going back into the tank due to the pump valve not hold the pressure.

George Z · 07-26-2015, 04:47 AM

Probably time to replace the two way valve. Seems to be bypassing water when closed.

Bill767 · 07-26-2015, 04:58 AM

I agree that it could be going back through the pump. It's happened to me.

rlbow43 · 07-26-2015, 06:09 PM

Thanks guys. At least I now have a place to start looking. I did replace the original water pump last Feb when in Death Valley. No problems since then until last week. At least I didn't notice any. Will get to looking. Thanks again.

rlbow43 · 07-26-2015, 06:42 PM

Quote:

Originally Posted by George Z

Probably time to replace the two way valve. Seems to be bypassing water when closed.

George,

That was my first idea, but I'm not sure how to get the old one out. Seems the water lines from that valve use the "pex" water lines and everything has a compression connection on it. As far as I can tell, I'd have to cut the lines to "break" into them. Maybe that is what I will have to do, and then put some unions somewhere in the lines so I could get into the area again if I have to.

You would have thought Monaco would have made it possible to take the valve out without cutting the water lines. But all the brass fittings exiting the valve cannot be taken apart from the front, and are connected with compression fittings on the pex lines behind the fiberglass panel the valve comes out of. I guess that should not be a surprise if you've ever worked on just about any rv these days.

George Z · 07-27-2015, 05:59 AM

Just put an off on valve in the line to the tank with shark bite fittings

ShapeShifter · 07-27-2015, 02:31 PM

Quote:

Originally Posted by Bill767

I agree that it could be going back through the pump. It's happened to me.

That would be the first thing to check, especially considering that the fill/city water valve is difficult to service.

Quote:

Originally Posted by rlbow43

I did replace the original water pump last Feb when in Death Valley. No problems since then until last week.

Were you on city water since the replacement? Was it long enough to fill the tank if the pump is leaking?

Were you using the pump since replacement? If so, did the pump ever run for a second or two every so often? That would be an indication that the pump is unable to hold pressure and is leaking back into the tank.

It might not be a hard failure on the pump, perhaps there is just a bit of dirt/debris on one of the tank check valves that is preventing it from closing completely?

A quick test would be to shut off the inlet valve of the pump, so that it is isolated from the fresh water tank. Then see if the water tank keeps filling. Rather than wait so long, if you have an input screen on the pump that you can remove, take off the cover and dry off the initial water that leaks out (make sure the valve from the tank is already closed.) Then, watch it for a while: does water keep seeping out of it? If so, that would be an indication that the pump is letting water leak backwards through it. If you have no input screen you can open up, you could do the same thing by disconnecting the pump inlet pipe (but not the outlet, that will be pressurized by city water.)

If all of these tests show that the pump is not leaking, then it's time to look at the fill/city water valve. But a ball valve like that is usually pretty reliable, a check valve in the pump seems like a more likely suspect to me.

mdc99 · 07-27-2015, 02:49 PM

I agree that I wouldn't anticipate the valve going bad. However here is what a p.o. did on my unit, I can only presume it was due to a bad valve. Seems to work good.

Jeff753 · 07-27-2015, 09:37 PM

Probably not it but perhaps a physical look at the tank level to see if it's really full. Mine has shown half full (which is correct) and then it will show full the next day even if I have not taken in any fresh water. Next day it shows half again. My issue might be a loose sensor on the tank but it's only done it twice so I haven't opened the bolted tank door to look.

Jeff
2001 Dynasty Regent tag axle
Cummins 350 8.3 ISC

rlbow43 · 07-28-2015, 02:51 AM

[QUOTE=Jeff753;2669470]Probably not it but perhaps a physical look at the tank level to see if it's really full. Mine has shown half full (which is correct) and then it will show full the next day even if I have not taken in any fresh water. Next day it shows half again. My issue might be a loose sensor on the tank but it's only done it twice so I haven't opened the bolted tank door to look.

Jeff

Pretty sure the tank was full. I realized there was a leak when I saw the overfill tube leaking steadily, and then checked the gauge and it was at 100%. Gauge has always been accurate. It always overflows right after the gauge reaches 100%. No reason not to trust it.

I've dumped the fresh tank so I can unhook that side of the pump. Then I will hook up the hose to the supply side and see if water comes out that side of the pump. If so, check valve in the pump must be leaking. I've got a bunch of things to do to the coach so we can take off to see family in the midwest (Kansas & Oklahoma) about mid-August. Have my hands full.

rlbow43 · 07-28-2015, 03:07 AM

-----------------------------
Q: Were you on city water since the replacement? Was it long enough to fill the tank if the pump is leaking?

Rod: Yes, but I don't think long enough to fill the tank. Other than that, I hooked up to fill the tank to sanitize it, and then fill it, but didn't leave the pressure on when not filling.

-----------------------------
Q: Were you using the pump since replacement? If so, did the pump ever run for a second or two every so often? That would be an indication that the pump is unable to hold pressure and is leaking back into the tank.

Rod: Yes, but didn't notice the pump cycling like that.

-----------------------------
It might not be a hard failure on the pump, perhaps there is just a bit of dirt/debris on one of the tank check valves that is preventing it from closing completely?

Rod: Where would I find such 'tank check valves'?

rlbow43 · 07-28-2015, 03:12 AM

Quote:

Originally Posted by mdc99

I agree that I wouldn't anticipate the valve going bad. However here is what a p.o. did on my unit, I can only presume it was due to a bad valve. Seems to work good.

I'd really like to stay with the same type of valve, but that looks like it would do just fine.

ShapeShifter · 07-28-2015, 06:08 AM

Quote:

Originally Posted by rlbow43

Rod: Where would I find such 'tank check valves'?

It's inside the pump.

This is how a typical diaphragm pump is set up. The motor causes the diaphragm to move in and out, increasing and decreasing the internal volume of the pump chamber. As the volume increases, water is drawn in through the inlet check valve, while the outlet valve prevents back flow. As the volume decreases, water is pushed out the outlet check valve, while the inlet valve prevents back flow.

When using city water, the pump is off, but the outlet side of the pump is pressurized to the city water pressure. While a slight leak in those valves won't affect pumping operation, any leaks in those valves can cause the city water pressure to force water backwards through those valves into the fresh water tank. It may only be a slight trickle, but over time the effect can add up.