Use gray to flush black

I would suggest that you find a flat pan and collect the shower water as you stand in the pan. Some might miss it's mark, but pour that into buckets, maybe through a strainer to collect the hair. There is small lines and valves that water has to flow through, and the use of gray water as a flusher could lead to a lot of problems if something that went into a gray tank gets stuck along it's path, or causes gate valve problems in the toilet.

I pour dishwater down the toilet.

Run the water that you waste to warm up the shower into a bucket and use that. I would use the gray water. I have a clear section of sewer pipe and the first glug of gray water is pretty nasty with solids and coffee grounds.

When our gray water tank starts to get full, we open the valve and drain some gray water into a bucket and then pour the bucket into the toilet. Both the gray and black tanks are 25 gallon, but we generate about 5 gallons of gray water a day and maybe one or two of black water. So this "bucket brigade" helps extend the time that we can boondock, and it also dilutes the black water.

A pump would be very useful, but I am not sure how to plumb it safely.

I installed a gray water transfer pump. Cut a "T" into the 1½" gray water drain line. Plumbed pump output into the black tank vent stack, about 1' above the tank.

Richard

We use a Rubbermaid dish pan to do dishes in the galley...then use this soapy water to flush toilet....but only when our gray tank starts to get full and we aren't on a sewer site...

As with everyone...gray tank fills much faster than the black..

I'm with mockturtle and use dish water kept in a pitcher in the adjacent shower. I collect some shower water too.

I have a third "master" valve on the waste water outlet that can be closed while both the black and grey valves are opened, allowing the tanks to act as a single large tank.

The question wasn't about using gray water to flush out the black tank, but using it to flush the toilet. I think I've read here of one or two people who have rigged something up to do that. It's basically just installing a suitable pump and running some water lines to it. Probably having a selector valve to let either the fresh or gray water be used for flushing (and a check valve for the fresh water line to prevent any possible cross-contamination from the gray water) would be a decent idea in case one needs to go potty before anyone has taken a shower or washed the dishes.

Note that the gray water can get pretty stinky over time. For the amount of fresh water that would be saved, I don't think I would bother. RV toilets don't need a lot of water to flush.

DrewE wrote:
The question wasn't about using gray water to flush out the black tank, but using it to flush the toilet. I think I've read here of one or two people who have rigged something up to do that. It's basically just installing a suitable pump and running some water lines to it.

Correct ! Clearly some kind of strainer needs to be used to prevent hair, etc from clogging the pump.

DrewE wrote:
Note that the gray water can get pretty stinky over time.

Noted !