The PVC plumbing under the kitchen sink likely was leaking, and the
last guy who had this house silicone caulked the OUTSIDE of all the
joints. He must have been an interesting guy...we have been undoing his
work for 5 years

There is a small leak we can't find...but sometimes the floor is wet
and it always smells damp and funky under there.

Rip it all out and start over? It has to wait for money available. I*s
there a dye or something we can use in the drain to see where it is
leaking?

The 2 sinks are joined by PVC pipes coming from the sinks to a right
angle fitting, run about a foot of level pipe, and meet in the middle
at another rt angle fitting and go down a common drain. It was clogged
up badly...one sink water level would rise when I plunged the other. I
fixed it by using 2 plungers...one in each sink, with a helper, and
plunging the he** out of it. Now it runs free.
The dishwasher drain is plumbed into one of the pipes so close to the
sink that it shoots up into the sink, fills it, and the DW fills with
water after running if the sink is slow draining
It's one of the worst setups I have ever seen, but we need to live with
it for a while.

Any thoughts?
Debi.
Is a one-way valve a good idea for the DW?