Fresh Water Drain Mystery...

[sparkmanw]

We bought a new 2020 Grey Wolf MT Memorial Day weekend and headed west. Before departing, I put approximately 5 gallons in the fresh water tank just to have for parking lot overnights. After nearly a month of full hookups, I knew it was time to find the freshwater drain. Directly between the two driver's side tires was what appeared to be the overflow tube and next to it drain for the tank, so I removed the cap and to my surprise, probably 10-15 gallons of water came out... and after we'd used a good bit of it! Couldn't believe we'd been hauling around that much water. Back inside, the water lines were still pressurized, so I figured the dealer must have filled the fresh water during set up and kicked myself for hauling all that weight around! Got home two months later and opened the fresh water drain again, another 4-5 gallons came out? Went to the official "low point drain" and opened both hot and cold. Cold was nearly dry while hot drained another 5-6 gallons. What am I missing? How did all that water get back in the fresh tank if I thoroughly drained it? Why did cold water low point have no water in it, but hot did? Are there two cold low points? Have I still not found the fresh water drain? Why is the FR owners manual so vague on everything? Thanks ya'll!

[Reverse_snowbird]

This will sound like an odd question, but were you hooked up to a campsite water connection? There is a water pump check valve that can cause the fresh water tank to fill without your knowledge when you're hooked up to water. If that happens again, you can try this procedure that I stole from another post:"1) Turn off city water at the source;
2) Turn on your water pump and open-and-close various faucets in your camper allowing the water pump to cycle on and off;
3) Turn off water pump, open a faucet and relieve water pressure;
4) Turn city water back on.
You probably already know this, but the fresh water tank low point only drains the fresh water tank and it's hard to get it all out of there. Moving the rig probably put more of the leftover water toward the drain. Some of us open the drain while we're towing the trailer to get rid of excess water, but that is controversial.

When you open those blue and red low point drains, make certain you open the faucets to get the water out of the lines. Did you have the water pump on? That might have drained the water out of the hot water tank, but not sure how exactly.

[Qwkynuf]

Were you on "city water"?

There are at least two possibilities:

1) The check ball on your pump is leaking and allowing pressure to leak through the pump and into your fresh water tank

2) Someone used the "Shower Miser" valve in the shower. That valve turns off water to the shower head and diverts it back to the fresh water tank. The idea is to recycle the water that would ordinarily go down the drain while waiting for the shower water to get hot. There is no reason to use that valve while on city water, unless you actually want to fill up the fresh tank in anticipation of needing the water later.

[sparkmanw]

Thanks, you both asked if I was hooked up to city water (affirmative) and mentioned the check valve. I will try this procedure. Just weird the cold water part of the system apparently emptied easily through the fresh tank drain. As if there was no check valve, yet the fresh tank was by no means full?

[HangDiver]

One other thing I'll add is to be sure to leave the water pump OFF when you are hooked up to City Water as that can cause the check valve to open and fill your fresh water tank.

[Qwkynuf]

Originally Posted by sparkmanw

Thanks, you both asked if I was hooked up to city water (affirmative) and mentioned the check valve. I will try this procedure. Just weird the cold water part of the system apparently emptied easily through the fresh tank drain. As if there was no check valve, yet the fresh tank was by no means full?

The cold water side (either side, really) should not drain into the FW tank - it would have to go backwards through the pump to get there. And the "low point drain" is called that because it's the lowest point in the system - so any water that is in your cold water side should drain out through there, not into your FW tank.

If your faucets are open, you will get a lot more water from the hot side because it would drain the water heater as well.

[Larry-NC]

Originally Posted by Qwkynuf

If your faucets are open, you will get a lot more water from the hot side because it would drain the water heater as well.

Hmm. I'm not sure about that. The typical residential and RV water heater is plumbed with cold coming in the bottom and hot coming out the top. The design encourages laminar filling of the heater when you are showering. Laminar means layered--the cold water comes in the bottom, the hot water goes out the top with minimal mixing. This keeps the shower at the same temperature until the tank is nearly exhausted.

So if you relieve pressure from the system and then open the hot drain, it will only drain a bit from the top of the heater tank. But if you open the cold drain, it will almost completely empty the tank, an extra 6/10/12 gallons of water.

[Qwkynuf]

Originally Posted by Larry-NC

Hmm. I'm not sure about that. The typical residential and RV water heater is plumbed with cold coming in the bottom and hot coming out the top. The design encourages laminar filling of the heater when you are showering. Laminar means layered--the cold water comes in the bottom, the hot water goes out the top with minimal mixing. This keeps the shower at the same temperature until the tank is nearly exhausted.

So if you relieve pressure from the system and then open the hot drain, it will only drain a bit from the top of the heater tank. But if you open the cold drain, it will almost completely empty the tank, an extra 6/10/12 gallons of water.

Ahh, good point. I take mine back...

[larwil]

I am having the same problem. My fresh water tank is filling up in about 24 hours while hooked to city water. I have tried the idea of turning pump on and off and opening faucets to no avail. I am wondering, since i never use my fresh water tank if perhaps i could put a turn off valve somewhere in the water line so that water could not get into fresh water tank. If so, where would i put it? Thanks for any help on this issue
Larry

[Larry-NC]

Originally Posted by larwil

I am having the same problem. My fresh water tank is filling up in about 24 hours while hooked to city water. I have tried the idea of turning pump on and off and opening faucets to no avail. I am wondering, since i never use my fresh water tank if perhaps i could put a turn off valve somewhere in the water line so that water could not get into fresh water tank. If so, where would i put it? Thanks for any help on this issue
Larry

There is a check valve (one-way valve) near or inside the water pump that allows tank water to flow into the system when the pump runs. It should block city water from flowing backward through the pump into the tank. Sometimes a tiny particle blocks the check valve from completely closing. It could be a bit of sand, a bit of hard-water calcium, or something picked up from your hose.

You may not have tried the best sequence to clear the check valve. Please try these steps in sequence.
Turn off city water.
Relieve pressure by opening any faucet
Run the pump. (This flows water through the check valve in the normal direction and should flush out any particles.) You could turn the pump on and off a few times.
Turn off the pump.
Turn city water back on.
Turn off the faucet.

You could put in a valve, but many people who have this problem use a better solution. You simply install a second check valve. Place it after the pump, on the trailer plumbing side, not the tank side.

Here is a sample with male threads on both ends.

And here is a sample with male threads on one end and female threads on the other.

These are the first two I found, not specific recommendations. You can probably find cheaper ones or find them locally. They are pretty common.