Need advice

[Silverback74]

I have a 74' 31ft Excella 500 I'm currently working on it and need to know if there is a way to just use a black tank for the toilet,shower and one sink in the kitchen?

[TG Twinkie]

Doesn't your coach have a grey water tank?
Is the black water tank below the floor?
Typically you will creat much more grey water than black.
Why would you want to do this?

[azflycaster]

a 74 31' 500 came with two waste tanks. The rear and mid baths had different size tanks, but neither was very big by today's standards. Expanding grey capacity with a portable tote would be a better option to extend your camping days, IMO.