holding tank capacity

stiffwind · #1 (**permalink**) 10-20-2010

I am having to replace the original built in fiberglass holding tank (25 yrs old) with a new tank..any experience out there about what should be the acceptable capacity for a new holding tank on a 37'?

St Anna · #2 (**permalink**) 10-20-2010

Hi,
I use a 48L, because it fits into the locker. You can get bladders (I personally dont use) but they can be taylor made or fit intothe bilge.

So, whatever the bigest size that can fit into the space.

Good luck, it is a Pain!

sailingdog · #3 (**permalink**) 10-20-2010

I'd second getting the largest tank that will fit. The size of the boat matters less than how many people will be using the head and for how long.

According to Peggie Hall, the average person uses the head FIVE times a day. If you figure the head uses 1.5 pints per flush, you're looking at 15 pints per day for a couple...or basically TWO gallons per day per couple. So a fifteen gallon tank would last about a week.

remetau · #4 (**permalink**) 10-20-2010

Quote:

Originally Posted by sailingdog

I'd second getting the largest tank that will fit. The size of the boat matters less than how many people will be using the head and for how long.

According to Peggie Hall, the average person uses the head FIVE times a day. If you figure the head uses 1.5 pints per flush, you're looking at 15 pints per day for a couple...or basically TWO gallons per day per couple. So a fifteen gallon tank would last about a week.

That is about right. We have a 15 gal and it lasts the wife and I just over a week.

stiffwind · #5 (**permalink**) 10-20-2010

thanks Don...but I'm curious if you have a manual head, how many pumps do you typically use to flush? The reason for my question is that my system design requires the waste to be flushed above the level of the head thru hose that fishes into the sink cabinent then up to the top of the tank...then tank is emptied then by gravity to thru hull if your offshore. So I'm using 20 pumps to make sure the waste completely empties up and into the tank...but I'm afraid that results in filling the tank too quickly

stiffwind · #6 (**permalink**) 10-20-2010

anyway, it sounds like a 16 gal new tank, the largest non-custom tank that will fit in the space, will be adequate

sailingdog · #7 (**permalink**) 10-20-2010

Stiffwind—

You might want to actually test to see how many pumps it takes to clear the waste from the line... 20 pumps may be overkill. If you can use just the minimum number that clears the waste from the line, then you'll maximize the amount of time between pumpouts.

stiffwind · #8 (**permalink**) 10-20-2010

and that test would be performed how?

remetau · #9 (**permalink**) 10-20-2010

We did have a manual, but now we have an electric.

It usually took about 10 to 12 pumps to clear the hoses, but we would flush for water for a few pumps and then use the dry setting for the remainder.

stiffwind · #10 (**permalink**) 10-20-2010

Are you happy with the electric head v. manual...or it it just another potential maintenance issue? Was the conversion difficult or expensive?