View Full Version : Drain valves, is two better than one?

05-22-2020, 02:49 PM
So I was thinking the other day. Our first trailer had one drain for gray and black water. It seemed that thing took for ever to completely drain both tanks thoroughly including using the sani-flush.. When we bought the new trailer I was a little disappointed that it had separate drains for each. But after two trips I'm pleasantly surprised we can drain both tanks at the separate valves and use the black flush quicker than before. Granted the new trailer tanks are 30 gal and the old were 40, but don't think that is making a big difference. When my wife mentioned it I told it must be because the drains are a straight shot right out of the tanks with no bends to navigate. I do have a Y-connector set up for when we camp with sewer hook ups, hopefully get to use those when Pismo Coast Village opens back up. I know exciting post, but I'm bored.:lol:

05-23-2020, 06:34 AM
Interesting. I have limited experience, but have never seen a small trailer set up with separate 3" drains for the gray and black systems. Having 2 drains, one on either side of your axles/tires is going to complicate the dumping process. As you note, you will need to set up two drain hoses with a Y connection for hookups. This always poses problems as you try to "walk the drain hoses dry". Your dump station time will increase. And you lose the ability to fully "flush" your black drain system with your gray tank water. I would consider this system a minus in a small trailer. They probably did this under the guise of "weight saving"...but how heavy is 10' of 3" plastic pipe? I'd guess it was more a matter of "cheaper".

I do have some experience with this issue. Our 40' toy hauler with 2 bath rooms has two separate drain systems, but you sort of expect this with the really big rigs. And yes, it is a bit of a pain to deal with...but in our case, it is worth it for that second bathroom!

05-23-2020, 08:43 AM
Placement of tanks is most likely the product of both trailer size and floorplan. I've seen big fifth wheel units with a mid kitchen and front bath so only two tanks and valves with one termination fitting. I've also seen smaller trailers with a front bath and rear kitchen that will have 3 tanks and two separate termination fittings.