Holding tank capacity

[relamb]

Last season I had the slip closest to the bathroom at the marina.  This year, we have the slip farthest from the bathroom, so we decided to use the head for the first time a couple of months ago.  It's the original 1988 CP27 tank and system as far as I can tell, and seems to work perfectly.  Used it maybe 5-6 times this summer for "emergencies" with no leak or smell, and getting ready to do the first pump-out soon.

I'm guessing maybe it fills the tank 1/2 gallon per use, so there must be 3 gallons of waste in there now, plus a gallon of RV antifreeze I flushed in last winter just in case there may have been something in it from the prior owner.

So the questions are a) How do you tell how full the tank is, or when it's completely filled?  and b) how many "uses" do you typically get per gallon of tank capacity -is my half gallon estimate correct?
Rick

[relamb]

Ok, further web research suggests that people who try to use the head sparingly fill the tank at a rate of about 1 gallon per day, per person.  Sound right?

[Allure2sail]

HI:
Sounds about right. I switched over to a larger holding tank, 10 or 12 gallons and get a week of cruising with an occasional guest. My new tank is plastic so I can readily see the waste level inside.
Bruce
S/V Allure
Swansea, MA