Problem when filling fresh water tank

Hey RVers,
When I am filling my fresh water tank, with all sinks, and shower valves closed, water enters my toilet bowl and (has) will overflow if I don't flush before it does so. I discovered when filling the fresh water tank with the sink cold water valve open it prevents water from entering the toilet bowl while allowing a slow steady stream coming out of the sink faucet. Simple solution!

But I don't understand why this occurs because the toilet has the foot valve and it doesn't leak. I'm interested in hearing what some of you have experienced. My owners manual doesn't mention this situation. I have a 31L Four Winds, C class, 2013.

Thanks in advance for your comments.

I gather your coach fills the tank via the city inlet rather than a gravity tube (unpressurized filler port)?  And that the toilet bowl doesn't overflow when connected to city water in normal use (not filling the tank)?  That really defies my imagination as to how the plumbing was done!

Obviously it should not do that. Even if the water system is fully pressurized while filling the tank, the toilet's flush valve should be adequate to prevent backflow into the toilet bowl. I think I would change the flush valve, just to be sure.

Typically the fill/use valve by the city inlet just opens a secondary path to allow water to flow past the pump and into the tank. The main water line remains open so some water reaches the faucets and toilet, but usually at much reduced pressure (because so much water is flowing to the tank). Somehow you are getting enough pressure to push into the toilet bowl or faucet. Bizarre!

It sounds like, by opening the bathroom sink's faucet, you're relieving pressure on the toilet's flush-valve so it doesn't leak and fill the toilet. But when you don't open the faucet, the valve in the toilet lets water flow past it, because something in the valve is broken or just not seating properly - i.e. it's the weak link in your water pressure system. Does your toilet overflow when you're unhooked from city water with the water pump on? When the water pump is on, does it intermittently run every few minutes, even though there's no water being used?

I'm having a hard time understanding how a valve would leak while being pressurized by one source (city water), yet not leak while being pressurized by the water pump - unless the pressure from the city water is excessive. Hmmmm...

Kev

Me too, Kevin. If the flush valve leaks or gets bypassed somehow when under pressure, it should leak whenever city water is in use or the pump is on. Something very strange is happening!

I think I didn't give enough/correct information. No city water is hooked up. It's just my garden type hose filling the fresh water tank (I remove the cap and put the hose in. The auxiliary pump is turned of. Water never seeps into the toilet when I'm hooked up to city water (I run the pressure between 55-60 psi. That makes me tend to think the fill/flush foot valve is working properly. I do like your idea that the toilet valve could be the week link. Do you still think that's possible after this additional info?

Thanks, I always welcome help, contributions, etc. from folks like you.

OK, so the pump is OFF while filling?  No water pressure in the system at all?  Does the water start coming into the bowl immediately when you start filling, or does it take awhile? How full is the tank when it happens?

I hate to ask this, but are you sure the port you are using is a tank fill port? The filler tube wouldn't even connect to the water lines to the faucet & toilet - it just dumps water into the tank direct.  Without the pump on, no water moves from tank to the water lines and no pressure in the lines.

lucille said:

Hey RVers,
When I am filling my fresh water tank, with all sinks, and shower valves closed, water enters my toilet bowl and (has) will overflow if I don't flush before it does so. I discovered when filling the fresh water tank with the sink cold water valve open it prevents water from entering the toilet bowl while allowing a slow steady stream coming out of the sink faucet. Simple solution!

But I don't understand why this occurs because the toilet has the foot valve and it doesn't leak. I'm interested in hearing what some of you have experienced. My owners manual doesn't mention this situation. I have a 31L Four Winds, C class, 2013.

Thanks in advance for your comments.

Click to expand...

My 1st MH would pressure up my water lines. I assumed it was because it took so long to fill the tank. That way we could use the water as needed while the tank was filling.

Are you using the brass  pressure regulator on the end of the hose? If not. I would think the toilet valve may be the "default" pressure dump to save your water lines from bursting somewhere else? I would think that the toilet would be the worst possible place for something like that. But you never know these days.

RobertB said:

My 1st MH would pressure up my water lines. I assumed it was because it took so long to fill the tank. That way we could use the water as needed while the tank was filling.

Are you using the brass  pressure regulator on the end of the hose? If not. I would think the toilet valve may be the "default" pressure dump to save your water lines from bursting somewhere else? I would think that the toilet would be the worst possible place for something like that. But you never know these days.

Click to expand...

The OP says, "No city water is hooked up. It's just my garden type hose filling the fresh water tank (I remove the cap and put the hose in. The auxiliary pump is turned of".

Rene T said:

The OP says, "No city water is hooked up. It's just my garden type hose filling the fresh water tank (I remove the cap and put the hose in. The auxiliary pump is turned of".

Click to expand...

Whoops. I missed that part of the discussion  :'(

I'm a bit confused here.  As I understand the situation your water pump is off, you are filling your fresh water tank by gravity with no pressurized connection to your water system, your toilet does not fill with either pump on or city water connection.  What happens before you put the hose in the gravity tank fill?  Is there an accumulator in your water system somewhere on the discharge side of the pump.  I missed whether this rv is new to you.  If not; is there any history of this happening.  Do you have the kind of toilet which can be filled by holding the foot pedal in a particular position? Dan

Dan,
You're not the only one who's confused. It doesn't make any sense.    Maybe she can elaborate a little more to help us understand.  :

All good questions, Dan. We are ALL confused about this, since what lucille says is happening seems to be impossible. But we've discovered the "impossible" in RVs before...

Good point Gary,  there seems to be a lot of "this one is different" with RVs.  Dan

I'll try to respond to several questions at the same time. I bought the RV new, it's a 2013 class C. I don't recall the problem happening until maybe a year ago. My wife said, hey where did this water on the floor come from? Dumb me, I never looked in the toilet. Anyway, there is no pressure in the lines, I'm just filling the fresh water tank. At to what level of fresh water does this begin ......I'd say within a few gallons and continues a slow flow into the toilet bowl. Yes, I do have a foot pedal to flush/fill the toilet. I don't ever recall seeing the inadvertent filling of the toilet in the normal pressurized mode from city water pressure. When traveling we very seldom use the toilet with the aux pump.

Now that you all have given me more to think about, as we begin our trip in mid March, I'm going to use the aux to pressurize the lines and see if this happens at that time, and check it again with city water at a camp site. At least I know opening a faucet when filling the fresh water I can avoid the overflow. Rather than start a project that could get nasty my thought is to just open the faucet and keep on rolling.

If I learn something that would be of value to the forum I'll share with you. I'm am greatful to be a member with all the terrific help we share with others who love RVing. Until next time, thanks very much.

Ok... throwing my 2 cents in here.

I'm thinking that the fresh water tank "vent" or overflow tube is plugged, and when water is flowing into the fill tube the air in the tank can't get out fast enough and gets pressurized, then pushes the water into the pipes. The toilet valve is somehow the weakest point, so the water comes out there?

Not usually possible to build much pressure when using the gravity fill port. The hose isn't sealed to the inlet - it's just sitting in the opening. Certainly not as much pressure as when connected to city water, even in a low water pressure park.

Gary RV Roamer said:

Not usually possible to build much pressure when using the gravity fill port. The hose isn't sealed to the inlet - it's just sitting in the opening. Certainly not as much pressure as when connected to city water, even in a low water pressure park.

Click to expand...

Is the hose just sitting in the fill valve? Or is it pressed in to hold it in place?

If there is a valve that can be closed coming out of the FWT (winterizing valve?) closing it should stop the water from getting to the toilet and sinks.

srs713 said:

Ok... throwing my 2 cents in here.

I'm thinking that the fresh water tank "vent" or overflow tube is plugged, and when water is flowing into the fill tube the air in the tank can't get out fast enough and gets pressurized, then pushes the water into the pipes. The toilet valve is somehow the weakest point, so the water comes out there?

Click to expand...

srs713 may have a point. O-rings seal using pressure. The more pressure, the more it get's distorted in the O-ring groove and the better it seals.  When on shore power or using the onboard pump, you may get 20 to 40 PSI in the systems which may be more than enough for the O-ring seals to seal.  It may be possible that the water lines are just getting a tiny bit of pressure like maybe 1 or 2 PSI while filling the tank and leaking by a O-ring in the toilet valve.

I've got a couple of questions for Lucille. When you open the faucet while filling, is the water coming out of it just a drip or is it quite a bit of water flow?  Also, next to your fill port, is there a tiny hole with a screen (maybe 3/8") on it right next to the fill hole? This is the vent where the air escapes when filling. Water will also come out that small hole when the tank is overfilled during filling unless it's plugged.

If this is their problem how about getting a small piece of hose (maybe 1/2') to put on the end of your fill hose and stick that down into the fill port. This will allow more air to escape while filling and maybe not pressurizing the system. Or try filling the tank at  much slower rate.

Just a thought.......is the water fill at a higher level than the toilet? Perhaps something IS plugged enough to start a siphon of some sort and the toilet is the lower point? It does not really make sense but......

I've been reading and watching this thread. The only thing I can say is the toilet valve is leaking for some funky reason. So I would service that out with a o-ring kit or what it would take to rebuild the water valve. Then as for filling the water tank The only thing I can think of is like my old 1976 Dodge Jamboree had a very small fill point which a normal water hose would barely fit. Then the tank vent was very small. So I could see the filling pressure being high enough to push water down the line. (plausible) But still if the toilet water valve was damage and leaking then with the water pump ON it should still be leaking.

The only thing I could suggest is filling at a slower rate.