connecting grey tanks to get more capacity for the shower

Can't imagine filling a black tank with a capacity of 78 gallons....(That's a lot of flushes and a lot of $*1t).

Better to run one of the gray tanks into the black tank....This will also help it dump and clean better with the extra water.

downtheroad wrote:
Can't imagine filling a black tank with a capacity of 78 gallons....(That's a lot of flushes and a lot of $*1t).

Better to run one of the gray tanks into the black tank....This will also help it dump and clean better with the extra water.

Yes, I figured we could part of one of the grey tanks into the black.

I'm wondering if there's a way for one grey tank to share with the other grey.

Sure, we did it by making up a 3" pvc pipe with rubber elbow and 't' at opposite end with vallterra twist connectors on our 2 tank rig that had separate dumps. Simply put a valve on the end of the connector, open the dumpvalves, so that levels equalize.
On the next rig that had 2grays with one dump, we just made up a twist on valve to put on the dump, then open the 2 gray, even the black to let all the tanks equalize. Use all your waste capacity.

You can use a twist on valve at the main drain exit, if both gray tanks empty from there. You can just open both tank valves then to make one big gray tank.

Jerry

Here's an image I got off rvtrader that shows the dump valves. While the dealer states that there are two grey tanks, this photo seems to indicate a single grey tank valve.

Lexx wrote:
Here's an image I got off rvtrader that shows the dump valves. While the dealer states that there are two grey tanks, this photo seems to indicate a single grey tank valve.

You can't really tell by that photo alone.
My convenience center is similar to the photo but I have another set of valves that control my rear waste tanks. Those valve are located behind the tires at the rear of the trailer
I have 2 grey and 2 black tanks. I also have to discharge pipes.

downtheroad wrote:
Can't imagine filling a black tank with a capacity of 78 gallons....(That's a lot of flushes and a lot of $*1t).

Better to run one of the gray tanks into the black tank....This will also help it dump and clean better with the extra water.

Could put a 1-way valve in-between, to help keep the poop where it belongs. :-)

Lyle

I have 2 grey tanks on my Grand Design Reflection and I put one of the end of the 3" dump line.

Valetrra

This allows me to keep this valve closed and open both grey tank valves to tie them together.

When I dump my tanks close both grey tank valves and hook the stinky slinky to the outlet then open the Valterra valve and then the black and let the black drain and then you have both grey's to empty to rinse the slinky.

Lexx wrote:

downtheroad wrote:
Can't imagine filling a black tank with a capacity of 78 gallons....(That's a lot of flushes and a lot of $*1t).

Better to run one of the gray tanks into the black tank....This will also help it dump and clean better with the extra water.

Yes, I figured we could part of one of the grey tanks into the black.

I'm wondering if there's a way for one grey tank to share with the other grey.

I would not share a grey tank with the black, as you have no way of flushing out solids
From the grey.
I could see sharing the two grey tanks.

It's all 'waste'....grey tanks can be as nasty as black tank---even worst
Rotting food, rancid greases/oils, decaying hair, sloughed body cells etc

Past two trailers (1980 and 2007 models) I have added an 'extra' dump valve on the common drain header. With it closed I combined both black/grey on the 1980 trailer and all three (black/grey/galley) on present 2007 trailer)

Funny thing...no issues with odors (black or grey) cause the 'vapor barriers' as designed worked and dumping the waste tanks when FULL allowed for that WHOOSH factor (fast moving/high level river moves boulders)

If only the forward black/grey tanks share common drain header and rear grey has separate dump valve/line (as indicated by only one black/grey valve handles in wet bay center) then the extra valve on the forward common drain header will allow you to combine the forward black/grey 'waste' tanks.