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Old 05-01-2016, 06:38 AM   #1
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Can the Gray Tank "Spill" Out the Shower

So we've been camped in a State Park with no on-site sewer and the gray tank is at 98%. Normally, this wouldn't be an issue for me but this park is very hilly.

I don't know the mechanics of the Gray Tank but do we need to be concerned with water coming out of the shower drain and into the shower? Don't care so much about the shower; just don't want it coming out onto the floor!


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Old 05-01-2016, 06:43 AM   #2
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Do you still have your shower drain plug? I think if you fit it in tightly you shouldn't have a problem.

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Old 05-01-2016, 07:24 AM   #3
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I think that the shower pan is just the first place that you will see indication that your gray water storage system is at capacity and it is time to dump teh gray water tank!

No problem, but of you don't pay attention, the next thing will be that gray water spilling out of the shower pan onto the floor!

There are a number of simple tricks that have been posted by myself and others whereby you can extend your stay when camped with no sewer hook up in order to avoid having to drag your trailer to a dump site and return it to your site.

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Old 05-01-2016, 07:33 AM   #4
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We've been at 100% several times and made it through some tight campgrounds to the dump station with no issues.
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Old 05-01-2016, 08:59 AM   #5
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I would think that you will be fine. There might be a little that will slop out into your shower pan but I seriously doubt there would be enough to get past that. "Uneven"? It would have to be quite steep cause trouble.
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Old 05-01-2016, 10:47 AM   #6
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Wingeezer, tried searching for the simple tips you mentioned. Can you please provide the link(s).
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Old 05-01-2016, 11:24 AM   #7
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Pretty much every trailer including SOBs will come up the shower drain first. Your indicator is actually pretty accurate of you see water in the shower pan at 98%. Drain it now; don't push it further.
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Old 05-01-2016, 11:29 AM   #8
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I got an 1 1/2" test plug at Ace. As you screw it, it expands to snugly stop any spill over. Don
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Old 05-01-2016, 11:34 AM   #9
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Your gray water system consists of the following basic components, ranked lowest to highest:
1. Gray water tank dump valve and pipes
2. Gray water tank
3. Shower pan and plumbing
4. Kitchen sink and plumbing
5. Gray water tank vent (comes out on the roof)

Your bathroom sink probably drains into the black water tank. If it does drain into the gray water tank, it would rank between 2 and 3 on the list.

So, the shower pan is the true indicator of when then gray water tank is full and when stationary, the shower can hold approximately 10 gallons before overflowing onto the floor.

But your concern is the slosh, going to the dump station.

If the water is visible in the shower drain but not yet flowing into the shower pan, a tight fitting plug, as others have suggested, should be fine.

If the water is flowing into the shower, you will want to remove as much as possible before going to the dump station. A towel placed at the bottom of the pan along with a drain plug should neutralize any slosh of water you can’t bail out of the shower pan

To be absolutely sure, you can drain off some of the gray water into a bucket (the larger the better) using the gray water dump valve. Definitely a two person job as it is hard to position a bucket under the drain valve. Hopefully you have a hose you use to flush with that is not used for fresh water. You will also need to replace the dump valve cap with one that has a provision for connecting a garden hose. Hook the garden hose to the dump cap and position one person with the bucket downhill from the trailer. The other person is going to work the dump valve and will open and close the valve based on instructions from the person at the bucket. Important, make sure you know which valve is associated with the gray water and the black water (they are usually marked Waste and Sewer). Double check with your trailer user manual if in doubt.

You can take the bucket to the nearest restroom or dump station to empty out. Or, if your black tank has capacity, dump it down your toilet. Five gallons drained from a gray tank that has not yet overflowed into the shower should provide more than enough margin of safety from sloshing.

Disclaimer, common sense prevails here, I am not responsible for spillage or any other accidental issue which may arise following my suggestions.

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Old 05-01-2016, 11:35 AM   #10
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Using the "drain plug" method, really isn't going to change anything. The tank is full, that's the end of the story. If you "plug" your shower drain, in a very short time the grey water will be seen in either the bathroom lavatory, or the kitchen sink.....
You might as well either hook up and go to the dump station, or maybe your grey water drain valve could conveniently start leaking.....(not saying that you should start the leak, though)
Old age is coming at a really bad time!

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Old 05-01-2016, 12:39 PM   #11
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For goodness' sake - don't plug the shower drain to keep the gray water out unless it is an emergency and you are on your way to the dump.

If you plug the shower drain, where would you prefer the excess to build up?

We only had gray water back up into the shower once: the daughter-in-law volunteered to do the dishes and we didn't pay attention. So she ran the water continuously while she washed and rinsed and I was lucky to smell something a little funky and caught the matter just in time.

Somebody, please, point me to the road.

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Old 05-01-2016, 01:28 PM   #12
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I think you're all forgetting the air admittance valve!
These are not a check valve! They will leak if pressurized with water!
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Old 05-01-2016, 01:40 PM   #13
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Our grey backed up nto the shower. Get it dumped now, worth the trip.
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Old 05-01-2016, 02:11 PM   #14
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I have hit the road with a partially full gray tank a couple of times and have had it back up into the shower. I do not have or use a plug. I have a rubber drain screen to keep hair and cat litter out of the gray tank. My cat box lives in the shower. No harm no "foul". A bit gross but rinses out easy enough. So far no internal accidents from the black tank.

Do you know what a learning experience is? A learning experience is one of those things that says "You know that thing that you just did? Don't do that."
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Old 05-01-2016, 04:05 PM   #15
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What about using an horizontal check valve, in place of a p trap. It has a rubber bladder which allows water to go out but not back up. I think i got it at VAS
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Old 05-01-2016, 06:38 PM   #16
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I appreciate the help everyone. I really had no option but to go for it and hope for the best. As always, my wife was with me... so I made (begged) her to take the ride to the dump station in the shower while on the phone with me. Good news and bad news.

The bad news is that after a nightfall of rain, those trailer brakes were reeeeeally sticky and tossed my bride pretty good. She's fine! The good news is that there was no water at all. She did have the drain plug in but there's no way that thing would stop anything other than a bubble from coming out.

For reference the tank was actually at 95% upon moving. And now we know!

Thanks again!
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Old 05-01-2016, 09:02 PM   #17
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When the grey tank is full, the back-up reservoir, by default, is the shower basin. The second back-up will be the bathroom floor. LOL

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Old 05-02-2016, 07:42 PM   #18
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And for those that find themselves pushing the limits, the black tank shares the same vent stack as the grey tank (at least on our 19' FC). So if it comes to overfilling things and the shower is corked tight, I wonder if a little of the grey water would rise in the vent stack and find its way into the black tank? I think the black tank connection to the vent stack is below the sink drains.

If someone experiments, please make sure you include videos along with the dialog and photos!

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