Fill the holding tank before pump out?

[Dr. D]

I regularly pump out my boat's holding tank. This occurred to me the last time: Would it be beneficial to fill the holding tank with fresh (or raw) water just before the pump out? That would disturb all the stuff in the tank and dilute it. Or will that only make the time for complete pump out longer?

[rslifkin]

It certainly won't hurt anything to fill it up first. Every few pumpouts it's a good idea to pump the tank, refill at least partially with water and then pump it again to mitigate sludge buildup in the tank.

[S/V Illusion]

Or even better, pump out the crap, fill with clean water and then pump out again. The theory being you aren’t going to get much agitation by putting clean water in a partially full tank

[CrispyCringle]

Agree with Illusion.

[peghall]

There's a better way: pump out the tank, then add about 6" of water to the tank via the deck pumpout fitting 'cuz that sends the water into the tank at the bottom to stir up any sludge and hold it in suspension long enough to pump that out. Repeat, repeat till you're pumping out only clean water. If you have an overboard discharge pump add water one more time and turn on the pump to rinse it and its dedicated plumbing to rinse them out. Not necessary to do that every time you pumpout...2-3x/season or every 2-3 months if you use your boat year round and especially in preparation for winterizing or other extended layup.



--Peggie

[Dr. D]

Thanks, Peggie.

[GordMay]

Originally Posted by S/V Illusion

Or even better, pump out the crap, fill with clean water and then pump out again...

What I did. (wash & rinse)