The problem with the gray water storage on the 31SL is that the galley tank is plumbed to the kitchen sink and to the shower, and the gray water tank is plumbed to the bathroom sink and the washing machine drain. For many units which do not have a washing machine the gray water tank is barely used because the bathroom sink does not use much water.

A convenient solution is to tie the gray water tank and galley tank together by the use of a Valterra gate valve installed at the common drain outlet where the sewer hose connects. The valve is made so that it connects onto the normal hose connection, and the hose can be connected to the downstream side of the valve. Under normal use both the gray tank cable valve and the galley tank cable valves are left open, the black tank valve is closed and the Valterra gate valve is closed. This arrangement allows the gray tank and the galley tank to equalize and utilizes the full capacity of both tanks.

When dumping the system the sequence is to close both the galley tank valve and gray tank valve, then open the Valterra gate valve to drain the plumbing, then open the black tank valve to drain the sewage, then close the black tank valve and open both gray water and galley water valves. By draining the graywater last, the hose will be flushed out. A secondary benefit of installing the Valterra gate valve is that it prevents leakage from the tanks through the cable valves which sometimes collect a piece of debris and weep.

Other Redwood models may be plumbed differently but this same arrangement can be successfully used to expand gray water storage.

Yup, another option that works great for me is the Camco 39062 Dual Flush Pro Holding Tank Rinser with Gate Valve.

One word of caution though it can be hard when backwashing to know when the tank(s) are full so I got a Save a Drop water meter so I know how much water I have put in the tank when filling. Also works to know how much fresh water I'm adding to take with.

We have a similar arrangement since I shelved the W/D cupboard for additional storage.

Terry, a great write up! Just a comment that you may want to clarify, depending on the model the plumbing my be different. For example, on our 36RL the galley tank only drains the kitchen sink (and a dishwasher if we had one installed), the other gray water tank drains the shower, bathroom sink and washer.

Regardless, the solution is good, if we boondocked we could use the galley tank to take excess from the gray water tank.

Al.

Terry, a great write up! Just a comment that you may want to clarify, depending on the model the plumbing my be different. For example, on our 36RL the galley tank only drains the kitchen sink (and a dishwasher if we had one installed), the other gray water tank drains the shower, bathroom sink and washer.

Regardless, the solution is good, if we boondocked we could use the galley tank to take excess from the gray water tank.

Al.

Thanks. I didn't realize the plumbing was different. I modified the description to fix this.