So you fill the tank 1/4 full of this solution? or do you just use 5
gal of water for any size tank?

Put enough in the tank to get it into all the plumbing. If only 5 gal.
is enough to do that, then 5 gal. is all you need.

When we used to use fresh water flush it wasn't connected to the
toilet at all - we just used the shower head to flush the toilet with.

It has nothing to do with toilet flush water, Rosie...unless you care
whether the toilet flush water smells/tastes like chlorine or antifreeze.

However, using the shower head to put water in the bowl is not good for
the toilet pump...'cuz what's in the bowl is only passed through the
bottom part of the pump, leaving the rubber parts in the upper part of
the pump dry, which deteriorates 'em. If you have the typical electric
macerating pump, closing the seacock and only putting water into the
bowl causes the intake impeller to spin dry, which "fries" it with the
first flush and then will destroy the intake pump housing. If you've
done that, if you ever open the intake seacock again, water will flood
the bowl--overflowing it, if it's below the waterline--because there's
no longer anything left of the impeller to block it.

--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://shop.sailboatowners.com/books...ku=90&cat=1304