another couple of water tank questions

[kouka2]

Ok, thanks. I assume the pump prevents backflow (it has an arrow on it).

With the vent, do you mean I can use a small bore? So I could just run a piece of plastic tube to wherever as along as it was somewhere the smell won't bother me. That would be much easier. I have an indicator on the tank already. Will the small bore hose be enough allow easy emptying of the greywater tank?

[chev49]

the grey water tanks that i got out of several trailers and a motorhome all have 1 1/4 black plastic pipe for the vent.. In my bus, I put 3/4 inch tied together for the 30 gallon tanks and that works fine. I vent through the roof. The 3 inch roof vents are only a few bucks at camping world without the screen which can easily be stuck in there to keep the leaves and bugs out. Back almost 20 yrs ago, i started out with using 3 inch plastic pipe for all the plumbing, as it was mobile home code, and have slowly reduced things like vent size down because smaller size is far easier to install, and works fine.

[lornaschinske]

1.5" vent; 3" sewer drain with 2" threaded ball valve to 3" RV sewer hose; >3 minutes to dump 25 gallon black from unlocking the door to locking it back closed.

[kouka2]

It's greywater only (I don't have any black water). I've checked with the self containment regs here and the main thing is that the top of the greywater vent is higher than the outlet of the lowest drain in the truck, so that any overflow is visible in the sink rather than spilling on the ground (in my case that's the kitchen sink currently, later it will be the shower). They have a 10mm/.4" minimum which seems very small (my outlet will be 32mm/1 1/4" or 40/1 1/2"). But I have a hepvo valve under the sink instead of an S bend and apparently that acts as an air intake valve, so it may work out that the vent is just for smell prevention. I think I will fill the tank and drill a hole and see how it empties, and then just keep enlarging until I am satisfied. Do you think the length of the vent hose will affect how quickly the tank will empty, or is it just the diameter that is critical?

The hose will have to go horizontally under the deck to the front of the truck and then up.

[chev49]

just the diameter is important, but if you are using a hose... make sure it doesn't ever get a kink in it or that will kinda defeat your venting purpose..

[lornaschinske]

Vents also let stinky smells escape. That is why most vents for black & grey tanks terminate above the roof. We have had grey tanks get pretty stinky during hot summer months if we close the valves and hold the waste water. Since we usually are on full hookups, we leave the grey open and close only when we travel or have no sewer hookups. This is just our experience. Some folks waste tanks don't smell.