Water tank overflows-I may know why

[two2go]

I wonder if anyone has experienced this with their Nat'l RV?
When I sit hooked up to city water and my fresh tank is full or near full, there will soon be a continuous dripping from the rear bumper which is coming out of the tank overflow. Then, when I am not hooked up but am using the water pump, the pump will "burp" about every two minutes.
After looking at the complicated water schematic, I now conclude that the two-way valve that directs water to city supply or tank fill leaks and allows pressurized water to seep to the tank fill line. This is why the tank overflows, and also that the pump pressure is being reduced by the leakage and causing the pump to cycle.
When I return home and have access to all my tools, I will have to see if my theory holds water (snicker).

[two2go]

I wonder if anyone has experienced this with their Nat'l RV?
When I sit hooked up to city water and my fresh tank is full or near full, there will soon be a continuous dripping from the rear bumper which is coming out of the tank overflow. Then, when I am not hooked up but am using the water pump, the pump will "burp" about every two minutes.
After looking at the complicated water schematic, I now conclude that the two-way valve that directs water to city supply or tank fill leaks and allows pressurized water to seep to the tank fill line. This is why the tank overflows, and also that the pump pressure is being reduced by the leakage and causing the pump to cycle.
When I return home and have access to all my tools, I will have to see if my theory holds water (snicker).

[Richard S.]

The valve for City Water/ Tank Fill is leaking, letting water flow into the fresh water tank when you are hooked up. The same valve will let a small amount of air into the line going to the water pump and this will cause it to cycle at times. I have heard that you can tighten up the nut on the handle of the valve and it will stop leaking.
Good luck

[speed racer]

I hade this problem with my 2005 dolphin last year. After many test to find the path the water was taking I found the check valve in the water pump was bypassing and leting water into the tank from the presure side of the city water system. Rather than replace or rebuild the water pump I instaled a one way check valve on the presure side of the water pump. This also keeps the city water presure from the pump. I have had my MH hooked to city water here in florida for the last 5 months with no problems. T test this empty the water tank and diconect the hose on the tank side of the pump. Hook you city water up as normal and see if water comes out of the tank side of the water pump. Hope this helps.

[Blue Ribbon]

Slightly related, when filling my freshwater tank about 1/2 the time after it is completely full, it syphons out 1/3 to 1/2 ALL the water, and there is nothing I can do to stop it. If I fill the tank coach front end down, it never happens. Back end down, always happens, and level, well some time.

For long weekends, this is awful. Solution, put a ball valve on end of vent hose. When tank fills and starts running over, I close valve. Drive to site, and open valve and all is OK. Don't know why.

Dealer did put on a new vent hose, and there may be an issue there. But why when it is running hard - stop it from running- move the coach then open vent and it does not run. A pain in the butt, but I'm OK with this solution.

Even if after filling, closing the valve, moving coach, then parking back end down, open the valve and it does NOT syphon. I guess it is just the Water Gremlin.

[M&EM]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Blue Ribbon:
Slightly related, when filling my freshwater tank about 1/2 the time after it is completely full, it syphons out 1/3 to 1/2 ALL the water, and there is nothing I can do to stop it. If I fill the tank coach front end down, it never happens. Back end down, always happens, and level, well some time.

For long weekends, this is awful. Solution, put a ball valve on end of vent hose. When tank fills and starts running over, I close valve. Drive to site, and open valve and all is OK. Don't know why.

Dealer did put on a new vent hose, and there may be an issue there. But why when it is running hard - stop it from running- move the coach then open vent and it does not run. A pain in the butt, but I'm OK with this solution.

Even if after filling, closing the valve, moving coach, then parking back end down, open the valve and it does NOT syphon. I guess it is just the Water Gremlin. </div></BLOCKQUOTE>

BR,
NRV has used a double tank arrangement on some of there 34 foot models and perhaps others too. Mine has this arrangement and will do the "Water Gremlin" thing you describe.
The cure that works for me is to fill the fresh water tank slowly to allow the connection hose between the two tanks to equalize their levels. As the tanks reach maximum slower they fill at the same rate. A fast fill will indicate overflow sooner then when both tanks are full.

Try that and see if it works for you.

Marty

[two2go]

I see two parallel problems going on the National RV threads. One is siphoning. I have traced my problem to definitely being a leaking diverter valve. The middle valve on the water service panel is a three-way brass or bronze ball valve that directs the incoming pressurized city water to the coach water lines or to fill the water tank. When the valve is set to the normal service position (not tank fill) it leaks slightly back to the water tank from the pressure of the water pump or the city supply.
So the question is, does anyone know where to get a replacement valve or if it can be repaired? I have not tried local plumbing supply houses yet. Nor have I found a source on the internet.

[Richard S.]

The manufacture of the valve is WATTS http://www.watts.com/ Have you tried to tighten up the nut on the handle, some times this is the problem.

[two2go]

Richard S, thank you for the info. The Watts valve is the one, and I found a local supplier. Yes, I tried tightening the handle nut, but there is an internal leak around the ball itself apparently. I may take a belt and suspenders approach and also install a backflow preventer valve to the pump inlet just to be sure the water stays where it should. Now that I solved the winterizing inlet suction problem (my other thread-"Winterizing, this didn't suck"), maybe I will finally have a properly functioning system.

[Richard S.]

Glad things are looking up, when you have the water service panel down tighten up all fittings and the FOUR screws that hold the city water pressure regulator together. Mine were all loose from the get go.
Good luck,
Richard

[rogueii]

Ma--this brings back memories! I was on a 5 month trip in 2005 and had the same problem--When hooked up to city water, the tank would eventually fill and over flow, leaving a large puddle under the motor home.
I took the RV to National in CA and they replaced one of the Ball valves in the PLUMBING PANEL. I went to San Deigo, and the next morning it was leaking again. I had to turn the water off and use the pump, so as not to get the CG people upset. I called National RV and told them I was coming back in. They said they were too busy. I said I would be in they Service lot, hooked up when they opened on Wednesday and would stay until they fixed it.

They changed the Ball Valve again, But I stayed there and in the morning, the overflow had left a big puddle running down the parking area.
They took it back to fix again. They checked their supply of Ball Valves and said they must have a bad supply, finally found 1 that didn't leak. Changed it again, I left for Vegas and it started to overflow again. I was out of Coach Warranty and had paid $385 for this service. I called them and told them I could not come back, do to schedule and would go to the East Coast Service CTR. when I got home. I got an incident Number, and about 1 month later, made an appointment in Lakeland, FL. (Great PLACE, great TECHS.) 45 minutes (waiting for the Tank to overflow) IT was the Water Pump, with a bad check valve. Replaced the pump (under warranty) No problems since.

[two2go]

rogueii has got me thinking. I thought the water was going past the ball valve. It's hard to test the system to see what is really going on, but maybe all I need to do is pull the panel down leaving all hoses connected, hook up the main inlet to city water, put the valves in normal use position and disconnect the hose to the water pump inlet. If the pump check valve is leaking, I should see water coming out of it. I do have a new spare pump, so that would be an easier fix. Thanks to this forum for the ideas. I'll post what I find.

[speed racer]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by speed racer:
I hade this problem with my 2005 dolphin last year. After many test to find the path the water was taking I found the check valve in the water pump was bypassing and leting water into the tank from the presure side of the city water system. Rather than replace or rebuild the water pump I instaled a one way check valve on the presure side of the water pump. This also keeps the city water presure from the pump. I have had my MH hooked to city water here in florida for the last 5 months with no problems. T test this empty the water tank and diconect the hose on the tank side of the pump. Hook you city water up as normal and see if water comes out of the tank side of the water pump. Hope this helps. </div></BLOCKQUOTE>

[speed racer]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by rogueii:
Ma--this brings back memories! I was on a 5 month trip in 2005 and had the same problem--When hooked up to city water, the tank would eventually fill and over flow, leaving a large puddle under the motor home.
I took the RV to National in CA and they replaced one of the Ball valves in the PLUMBING PANEL. I went to San Deigo, and the next morning it was leaking again. I had to turn the water off and use the pump, so as not to get the CG people upset. I called National RV and told them I was coming back in. They said they were too busy. I said I would be in they Service lot, hooked up when they opened on Wednesday and would stay until they fixed it.

They changed the Ball Valve again, But I stayed there and in the morning, the overflow had left a big puddle running down the parking area.
They took it back to fix again. They checked their supply of Ball Valves and said they must have a bad supply, finally found 1 that didn't leak. Changed it again, I left for Vegas and it started to overflow again. I was out of Coach Warranty and had paid $385 for this service. I called them and told them I could not come back, do to schedule and would go to the East Coast Service CTR. when I got home. I got an incident Number, and about 1 month later, made an appointment in Lakeland, FL. (Great PLACE, great TECHS.) 45 minutes (waiting for the Tank to overflow) IT was the Water Pump, with a bad check valve. Replaced the pump (under warranty) No problems since. </div></BLOCKQUOTE>