Fresh bypassing into grey? 2024 Micro Minnie 2108TB

[Dashunde]

In a 2108TB is there any way a fresh city connection can sneak around and fill the grey without coming out a faucet and going down a drain first?

We usually boondock, but have done a few nights in parks hooked to city water. We pulled up to Glacier NP area around 3pm and by midnight after some cooking, dishes and two quick showers our grey tank is full??
The wife noticed because the shower stopped draining, then I found gurgling in the kitchen sink when the bathroom sink is used, and of course the red light gauge thing is lite up to “Full”.

I’m not sure how we would have filled our grey tank in just a few hours? We dumped in Darby MT just 5 hours before hooking up in Glacier.

[Morich]

You are correct and there is NO connection from fresh to gray. There are no connections directly between the two, even if really bad builder mistakes were made.
One is regulation for safety, they want NO chance of waste being in the fresh to make us sick!
The second is just the physical pipes involved. Drains are way big (1 1/4?) like the trap at the sink or bigger. Fresh water supply lines are small like 1/2 inch PEX. Even the worst, blind , drunk installer would have to search for special fittings to connect the two!
The tanks are molded with the connection points formed. To connect a fresh line directly to the tank would be a real trek to drill a hole and then find fittings to fit that hole to the fresh lines!

It is easily possible for the hose to find a failing check valve and overfill the fresh tank but no connection to the grey except from leaking faucets or valves to let water run.

A leaking stool valve can overfill the black but to get it into the grey it would have to also have leaking drains for black and grey, overfill the black to the point it backs into the grey. Possible in theory but not really likely! And you would notice the black full as well before coming up inside!
Almost certain problem is using more water than expected for RV purposes! Washing dishes is a different process in RV to save water!
It takes a bit to get used to "roughing it"?

[creativepart]

After dumping the gray tank in Darby, MT did you check the tank level when you arrive at Glacier? In other words are you sure it was empty when you arrived there?

There is no connection between the fresh tank and the gray tank except your kitchen and bathroom’s faucet/shower.

If you travelled with your water pump on it is possible that some faucet ran while you were driving.

[Dashunde]

Hi, thanks for the quick replies.
No, we didn’t push the button to check the grey level in Darby, but we have a clear plastic 90 degree elbow and could see the flow was heavy and clear and dropped off to nothing. Will definitely push the button in the future.
The 12v pump was off.

So is there in fact any check valve or other plumbing device that would allow city water into the grey tank without visibly going down a sink/shower drain?

[creativepart]

Originally Posted by Dashunde

So is there in fact any check valve or other plumbing device that would allow city water into the grey tank without visibly going down a sink/shower drain?

None that I can think of.

[Morich]

No there are safety regs on most things like this and any direct connection would be a really big hazard and certain to be a violation.
the problem with check valves is that they are famous for sticking and that would be too much hazard to even think of leaving as a possibility. Just not done!

But the physical side of somebody making a mistake is just too much as well. The parts are just not at all the same.
That puts it over into almost like you getting your shoes mixed up with your wife? The materials, the sizes, and the connections are so different, that it would take a real effort to get them confused to put them together!

The idea of a false reading is one which might happen pretty easy, though as the readouts are semi-famous for errors!
Have you found that the tank was actually full when draining? A false reading of full ? But that would be expected to still say full after draining.

But I think most people work out different ways to deal with the limits of RV use.
Some stay only where they have hookups that allow normal water use as they have a full time drain.
Others who want to avoid hookups sites, may opt for a little blue cart to take the excess to dump.
And still others work out water use to more what military folks may do. There are those who work it much like folks who learn to do navy showers or possibly cook, shave, and bath out of their helmet!
The trick is to adapt to what our equipment makes possible or adapt the equipment to what we find practical for our use.

[bigb]

As mentioned there are no possible connections between fresh and gray, this would be a plumbing code violation. The most likely cause is a leaking valve (the shower can be a sneaky one and go un-noticed) or the fact that you only have a 25 gallon gray tank which doesn't take long to fill.
The pressurized city hookup at the CG likely has more pressure and volume than your pump that you normally use.

[Downytide]

Those gauges are insanely inaccurate, sometimes ours would read 2/3 full in black tank after empty, and I can see the empty tank with flash light.

One thing thou, use a pressure regulator when hook up to city water, the first time we hooked up we started to find leaks, the pressure is just too strong.

[Dashunde]

Originally Posted by Downytide

Those gauges are insanely inaccurate, sometimes ours would read 2/3 full in black tank after empty, and I can see the empty tank with flash light.

One thing thou, use a pressure regulator when hook up to city water, the first time we hooked up we started to find leaks, the pressure is just too strong.

We were not relying on the gauge, we noticed that the shower was not draining… truly full.

We used to use a simple non-adjustable regulator and the pressure/flow in the shower was less than what we got with the 12V pump.
So we switched to an adjustable regulator and set it for about 60 psi (after external filter) and that seems to deliver about the same shower pressure as the 12V.

But I do wonder what the regulated pressure really should be…

[Downytide]

The pump is about 40-55psi.

[Littleboots]

We have a 2108TB and I love my water mixer drafting the shower. I fill up my fresh water tank by using that bypass from city water. Any of you guys know if that new water mizzer could contribute? We have not had that problem. Just troubleshooting with you!

[Horse54]

I'll tell you a story about what happened to me a few weeks ago that may help you. I pulled in to get fuel after driving about 4 hours without stopping. When I did, I saw water coming from the wet bay. Then I went back inside and saw that there was water on the floor in the bathroom and the area outside the bathroom. Typical first thought was....here we go with a big repair bill.

After saying a few choice words, I started looking around to see if I could figure out the problem. I found it and as usual, operator error. I left the water pump on and while driving the shower faucet turned itself on just enough for water to come through the shower head. It eventually filled the gray tank and emptied the fresh water tank. As I said, operator error. And, I was actually relieved this was the problem. Could have been a lot worse.

[Morich]

But the OP has asked if there is a way for water to get from the fresh water tank into the grey tank without going through a faucet at some point!
And that answer is still no and for all kinds of reasons that have been discussed.
No planned plumbing system as it would be a definite hazard to connect the two!
No practical way to confuse the plumbing as the drains and supply are so radically different , both in size, materials and connections!

Given enough time, effort and money to buy the right adapters and figure out how to do it, yes, it is "possible" but I can't imagine anybody wanting to risk their job to do the extra work needed!

Sometimes the easy, simple explanation is the correct one.
Most of us have found out how easy it is to use so much water that we fill the holding tanks and that is the easy explanation!
They even sell the little blue water tanks to haul off the excess!