I know that on the standard bottle of RV antifreeze, it says DO NOT DILUTE.  I cannot get all the water out of my fresh tank. The outlet is about an inch and a half above the bottom, which leaves about an inch and a half of water still in the tank.  Is there a type of antifreeze that requires dilution?  That way I could make use of that stupid leftover water.

Amanda

If you add some RV anti freeze to the water, it will offer some protection against freezing, even in a diluted form. It's doubtful that a small amount of water in the bottom of a open vented tank, will cause any damage if it were to freeze.

The type of antifreeze you use in the RV purging process is important to know. The RV antifreeze has a base ingredient of propylene glycol and is considered to be non toxic for humans. It is usually applied full strength from the container.

Ethylene glycol is used in machinery for freezing protection and is toxic for mammals. It should not be used in any potable water system. It can be diluted and is often used in a 50 to 50 ratio. This type of anti freeze should not be used in your LQ, or any vicinity where animals may be attracted to its sweet taste. It is deadly, and will kill painfully, over a long period of time.

Buy the anti freeze marked "RV", use it straight or diluted, and you shouldn't have any problems.

Gard

I only put the RV antifreeze into the lines. I don't put it into the tank.  Too hard to get it all removed. Whereeas  any antifreeze in the hoses, is pretty easily pushed on through when I'm ready to use the system.

Even if it freezes, A litte ice in the bottom of a big empty tank shouldn't be a problem. It has vacant space to expand into.