Bill,

You might consider white lithium grease. This comes in a "food grade"
version that is suitable for equipment used in food processing. I've
seen it sold in most hardware and automotive stores as well.

I believe it would be suitable to your application, but you might want
to insure that the particular plastic used in the Y value is compatible.
Also, you may want to make certain that the plastic value is actually
safe for drinking water.

Alternatively, you could simply replace the Y value with two separate
brass gate values and a tee. This would allow you to fill either or
both tanks simultaneously.

Hope this helps.

Robb

p.s. Many Y valves have a retainer clip inside that controls how you can
configure the opening; usually you can only connect the input to tank A
or tank B. One setting that is normally restricted is connecting tank A
directly to tank B and closing off the input. I would strongly urge you
to consider modifying you value to allow this, and leaving it in this
position when you are not actively filling the tanks.

Bill wrote:
I have two freshwater tanks with one filler pipe. I want to put in a Y
valve so that I can fill either one separately.

I looked at several in the ship's store. They all had grease in the plastic
rotating seacock-like valve. I don't want grease in my drinking water.

I guess I could try and clean them up before I install them. Is there
another solution?

Thanks.