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I'm installing my sink into my countertop soon. The last component I'm working to figure out is the sink drain. My sink assembly has a 1" ID barbed connection
Additionally, I have a grey water tank mounted below and am plumbing all grey water into the tank through the floor.

A couple quick questions:

1. What kind of hose should I use for the drain? I was thinking braided vinyl 1" ID. Any reason to use something rigid instead of flexible vinyl? I'd like to use this drain valve, and thus I have to use some sort of flexible tubing. I could adapt to something rigid if there's a compelling reason.

2. Do I need a trap? I don't quite understand RV plumbing of sinks and showers-are traps entirely necessary to avoid smells? I know of the hepvo valves-not sure exactly how I would install with vinyl tubing-probably some adapters. What other options do I have besides a typical trap? I've seen many with the jug under the sink design-do people just not worry about greywater smell?

3. Plumbing the grey line through the floor. With flexible and with rigid piping, anything in particular to know? I was thinking of adhering some sort of PVC conduit to house my flexible drain hose.

Thanks.
 

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I have no trap, drain to a jug under the sink and have had the dreaded gray water stink once. It was along the Gulf of Mexico and it was 90º+ and humid. I drained it rinsed it and my flex hose still stank! I got a little chlorox, filled the sink with water and added some, ran the drain as fast as I could, and that cured it. I carry that blue P-P chemical but it never occurred to me to use it. Duh.
BTW I use a clear vinyl hose from my fresh water jug to the pump. It grew mold inside on that same trip so the fresh water got Chlorox too. I drop a small Chlorine tablet in the fresh water tank once in a while now. We have stopped drinking from the jug. I have storage for 5 or 6 gallons of water from the grocery for cooking and drinking.

On second thought, we DO have a trap. It is a low profile camper trap. What we don't have is the flexible drain pipe sealed where it goes into the gray water jug so the effect is the same..... gag gas can escape into the camper. Our take is, if we ever get it again that Blue stuff goes into the gray tank after dumping.
 
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Hi,
I'd be a bit concerned about flexible tubing flattening out at the bends and restricting the flow enough to pick up bits that go down the sink. Maybe there is some form of the flex tubing that does not tend to flatten out in the bends, but the stuff I have worked with had a definite tendency to do this.

Maybe use rigid barbed elbows or 45's for the tight bends and flex for the rest?

I plumbed mine with regular rigid PVC and regular PVC trap, but not sure if that's really necessary? Grey water definitely develops a good stink in a day or two, but don't know if it would work its way up through the sink drain or not.
Mine looks like this: http://www.buildagreenrv.com/our-conversion/promaster-camper-van-conversion-galley/
http://www.buildagreenrv.com/our-co...-plumbing-and-the-fresh-and-grey-water-tanks/

It would definitely make for more efficient use of the space under the sink if you could get the flex tube to work.

My grey tank is under the floor, and in my case, there was no way to mount the grey water tank directly below the sink. I had to move it toward the center and on the other side of the exhaust pipe, which involved insulating the drain line from the exhaust heat, so, maybe, double check your grey water tank location if you have not already.

I tried not having a vent on my grey water tank, and found that this resulted (no big surprise) in very slow draining and lots of gurgles. I just added a short vent pipe to the top of the grey tank that only ran a few inches forward to a slightly higher point -- did not run it up through the roof as a lot of RVs do, and this has worked fine.

 

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I used a small camper trap on our sink. We go to a 6 gallon graywater tank with a reinforced flex hose.

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