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2022 PM 159 HT
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50 Posts
Discussion Starter · #1 ·
I'm placing my sink on the right side, just behind the open slider and would like the drain closer to the outer portion of the floor. Under the floor there is a frame rail running forward to back with plenty of room & in the right spot. The tank will be mounted on the other side to that frame rail. My question is will it drain into the tank with the large inlet at the bottom? Can't seem any other way to get it to the tank on the other side. Hope I don't have to drill it through closer to the inside edge of the cabinet. How are you running that drain line?
Thanks in advance!
 

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Yes, drain lines can enter the tank anywhere, top, sides, even bottom. However, if they enter below the top, once the tank fills to that level, grey water will start backfilling the drain pipe to match the level in the tank. The only problem with that is freeze risk for the drain pipe. Our sink drain enters about 2/3 up the tank, so we drain the tank more often if there is a chance it might freeze. I've read some people in warmer climates (Aussies) even tee their drains lines into the tank drain fitting at the bottom of the tank.

On the other hand, dropping down at the front of the cabinet isn't too bad if you keep it to one side like @free2roam did above. Ours is almost identical.
 

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2014, 138WB, High Roof, Gas, SW MT
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Hi,
I agree that the drain can come in low on the tank or even into the bottom of the tank and the water level in the drain pipe will be the same as the level in the tank.

If the pipe actually comes into the bottom of the tank and the drain pipe hangs down lower than the bottom of the tank, it will be more susceptible to rock damage when traveling on gravel roads. Our grey water drain pipe comes out at the bottom of the tank and has been taken out three times by rocks.

Gary
 

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Van #2 2021 EXT
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In our 2018 Build, I put the inlet 1.5” at the top of the tank. IIRC the tank I purchased was 16” wide & fit perfectly between the floor cross members. It was 8” deep so it was only exposed 4” past the cross members.

I figured out where the tank would be. Drilled a hole thru the floor. Temporarily positioned the tank & marked it for the “spin weld” 1.5” female threaded fitting.

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The photos are from my 1st build our 2018 PM. Our new build (I built the majority of it in 6 weeks after waiting for the van for 1 year), does not have an exterior grey water tank yet. I will get back to finishing that build in October(ish).

In 2018 without any adult RV experience, I tended to do my plumbing like house plumbing. I now consider that a little overkill. In regards to drainage, I did not want a “slow drain” or grey water smells. Hence the house drain pipes & “P” trap, etc.

In our 2021 Build we have a temporary interior grey water tank. It is a 7 gal blue cube water jug container & this Camco RV style flexible drain.

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I plan on an under chassis tank(s) & having 1.5” ABS with the HepvO waste valve instead of a “P” trap. I will install the HepvO vertically, but you can use them horizontally. I got the idea of this waste valve from @SteveSS ,,, thanks Steve !! 👍


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Why this waste valve is probably better for an RV;

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2022 PM 159 HT
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Discussion Starter · #7 ·
Great info everyone, I really appreciate it all and amazing builds. I think I'm heading to the "drill a new opening on the top route", running the drain closer to the outer wall of the van, using the Hepvo (sp) valve and call it good. I think I took something from everyone's post :ROFLMAO:. This tank is only for the sink and I don't normally run much water through it. The tank and drain will be above the rail frame and I can use the large opening for a drain if needed. Freezing isn't much of an issue in San Deigo or AZ. Thank you all!
 

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Technically, the water level should never be above the bottom of the floor unless the tank was over filled
Your grey tank also needs some kind of venting to allow air in/out during draining/filling. If you install a passive, always-open tank vent like I did (linked in post #3 above), it will also act as an overflow preventing grey water from ever backing up any higher.
 

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2016 3500 ext-ht
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878 Posts
Hi @Dirtrider

A “water level” can be used instead of a “builder’s level”.

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If you understand this concept, placing an inlet for your grey water tank falls under the same physics. Note both ends of the water level must be “to atmosphere” open.
and make sure not to have part of the water level hose in the shade and part in the scorching sun.
 
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