Grey Water Tank

We wanted to have the grey water tank size of about 20 gal (close to our 25 gal fresh water tank) and we wanted it to have the max clearance, so the obvious solution would be to put it between the frame beams of the van's floor, which gives additional 4 " of height to the tank volume without sacrificing the clearance. 

I could not find a good tank of needed parameters that would fit between the the beams and accommodate the passage of the rear break line, so needed to make it myself.

Luckily, I found on Craigslist a couple of cheap used grey water tank from a large motorhome, cut end pieces and made two smaller tanks that fit exactly between the floor beams:

Then I tied them under the floor and connected them one to another, thus creating one larger tank of about 20 gal:

Finally, I connected the tanks to the shower pan:

bathroom sink (both on the driver side):

kitchen sink :

and the discharge hose with valve (both on the passenger side):

All connection are done by 1 inch rubber hoses that fit tightly into the standard plastic plumbing connectors.