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Old 03-27-2016, 03:06 PM   #1
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Grey tank empty, monitor shows full

We recently bought 2016 SportTrek. It was used, but in great shape. We've had it out three times and we're having an issue with the grey tank indicator showing full when the tank is empty. I've also noticed that when the tank is full and I open the dump valve it seems to drain slowly.

We've tried filling 3/4 and adding a cup of Dawn dish soap. No help. Any other ideas?

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Old 03-27-2016, 03:15 PM   #2
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Has it ever read correctly? It could be a sensor problem. A 2016 should still be under warranty.

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Old 03-27-2016, 03:18 PM   #3
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First I would fix the draining problem.
If ig drains slow, thdn something is nlocking the drain, and you cant be sure the tsnk is actually empty..

Since ig is gray water, push a rubber hose up ghtough the drain opening to sed if you can remove tge blockage.


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Old 03-27-2016, 03:20 PM   #4
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You say that it drains slow when the tank is full.
This could be a dried up layer of solids, (food, hair, etc)
on the bottom of the tank with a small opening for liquid.
When you put the soap in did you use very hot water, and then drive
around letting it slosh?
It could be restricted sensors preventing proper reading, but I would
question the slow drain.
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Old 03-27-2016, 03:28 PM   #5
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It might be helpful to keep in mind that the grey and black handles might be switched. Low chance, but it's possible.

As to the blockage, try a garden hose as suggested or a drain snake.

As to the gauge reading, you won't know what to do about that until you can get the drain to start flowing normally. Whatever is blocking the drain could also be making the sensors read incorrectly. In some places, there are tank cleaning services.
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Old 03-27-2016, 06:46 PM   #6
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I'll snake the drain this week. That's at least a starting point.

It has not read properly since we picked it up three weeks ago. It is technically a used trailer, so 30 day warranty is all we have from the dealer. We've got about a week left.

When filling and mixing with dish soap, we used warm water (not hot) and drove about three hours with the soap sloshing in the tank. I'm concerned that the tank may not have been properly emptied by original owner, and has sediment. Just wondering, how difficult is it to remove the tank on a trailer with an enclosed undercarriage?
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Old 03-27-2016, 09:40 PM   #7
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I bet the sensor shows full probably because it is full. I think there is a blockage and it's just not emptying out fully. There has to be a blockage and so I would fix that first before any tampering with the sensors. The advice above is exellent. I would definitely do some back wash but make sure someone is inside to check for over flowing etc. Keep flushing the tank over and over again. Good luck.
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Old 03-28-2016, 04:04 AM   #8
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I use a Valterra Flush King to back-flush both the grey- and black-water tanks. It has these advantages over using a hose by itself:

1) Uses your standard 3-inch hose for draining
2) Can see if the flush water is clear (or not)
3) Can shut off hose right at the fitting

The fill rate on the Flush King is high enough that you need to keep a sharp eye (or ear) out for overflowing inside the coach- a problem made worse for you because your tank level sensor is not working. As "TheMatrix" advised, have someone inside, if you can, until you get used to how long it takes to fill the tank through the Flush King. Otherwise, just add flush water a bit at a time until you perceive a tank is nearly full.

Buy and use a garden hose (not your drinking water hose) to use for flushing. I don't think the Flush King has a check valve, so the potential exists for dirty water to get into the hose if you don't close the ball valve before opening the dump valve. At home, you can do what you want, but if on the road you should add a check valve to the flush hose setup.
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Old 03-28-2016, 08:28 AM   #9
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Could also be construction debris from the build process
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Old 03-28-2016, 09:08 PM   #10
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You still have warranty. I would take it back to the dealer and request they correct the problem. They have all the pieces there if needed.
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Old 04-01-2016, 11:03 AM   #11
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I agree with left over wood in tank. The first time I drained my brand new trailer I found wood in my stinky slinky. I have read it happens from time to time. Hopefully your dealer will be better about checking it than mine. They wanted to charge me for servicing my slow draining tank, on a brand new month old travel trailer. I bought a snake and fixed it myself. Not hard but not pleasant since it was the black tank.
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Old 04-02-2016, 06:04 AM   #12
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You say 30 day warranty from dealer but is there still a manufacturer warranty in place since it's a 16 and most RV's have a 2 year and I would hope it's transferable. I had a similar problem and just filled the grey tank until it was full which takes a little guess work with some bleach about 1/2 cup and some dish soap and left it for a few days and it drained right out. That worked for me. Water is the best solvent but it takes time unless you have a solid blocking it up. Previous owners have kids or poured grease down the sink??
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Old 04-02-2016, 07:13 AM   #13
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I installed a rinse fitting into my grey tank but before that I used to stick a garden hose into the tank through the valve opening. You can put a bucket under the valve while you are doing this and catch most of the stuff coming out.

It is hard to believe that some one screwed up the tank in that short of a period. There must be something stuck in the tank. You could also find someone with a probe camera to look inside the tank. Grey tanks are not usually a big issue to maintain.

I would take it back to the dealer while you still can and let them do the work.
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Old 04-02-2016, 08:37 AM   #14
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Here's the Flush King:
Flush King - Valterra FK-02/F02-4350 - Sewer Flushing

Here's a better but more expensive version:
Sewer Solution - Valterra SS01 - Drain & Flush Systems.

First thing is to be sure the holding tank is empty. Then if the back-flushing doesn't do the job to clean the sensors enough, then a flushing wand is your next step.

Flush the inside of the tank using a wand with a swizzle tip that will spray high-pressure water in all directions inside the tank to clean the crap off the sensors. Here's a wand;
Flexible Tank Wand - Valterra A01-0187VP - Sewer Flushing

Note the tank wand is primarily for use down the toilet into the black-water tank. Toilet paper or other crap often covers the sensors and then dries into a hard film, so you need the wand for your black-water tank anyway. But if your grey-water sensors are not working they may be covered up with soap scum or other crap so you need to clean the crap off the sensors. You'll have to remove some of the drain plumbing above the grey-water tank to get the wand into the grey-water tank. Yeah, it's a tough job. That's why the RV techs charge you so much to it for you.

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