Full Holding Tank?

[WanderingStar]

How do you know? I see electronic monitoring systems for them, but it seems overkill for an accessible tank. Do you just estimate? Or does everyone (else) have a monitor? I'm installing a tank in a cabinet in the head, I'll be able to access the side of the tank. What do you do?

[k1vsk]

Well, if it's a translucent poly tank, you can see the water level if the walls are clean and there is sufficient light. Otherwise, you already mentioned the alternative. The exterior capacitive monitors are the most reliable as well as easiest to install.

[CalebD]

John,
I'm not the Head Mistress or Master but I will tell you what I think I know.
K1vsk is correct that the translucent tanks can give you an idea of how full is 'full'. If all the plumbing is done correctly you will see and/or smell brown fluid coming out of your holding tank vents when someone uses the head and the tank is full.
The best advice I think I can give is to use a pump out station as soon as you can once someone has made a 'deposit'. The other advice I will use is to use your nose and discern if there is a nasty sulphurous smell to the air in your cabin. This kind of smell does not allow me to sleep to readily but your mileage may vary.
I'd advise using the Raritan holding tank treatment called 'KO' only and not using bleach or strong chemicals as per Peggy Hall's book "Eliminating Boat Odors".
I think the same rule that applies to reefing the sails applies to the holding tank; reef early and often. The more you keep it pumped out the less crap can sit in there and cause you problems later. The biggest problem I have with all of this is that the folks who leave the 'deposits' behind are not the ones who will have to clean it out later. Pump out early and often and you wont need to use the brown sludge coming out of the vent lines as an indicator that the tank is full.
This is perhaps the dark under belly of the sailing life as I think I know it. Pumping out the tank ain't all that charming but if you do it often enough and it is convenient then it is just part of the life.
Peggy Hall's book available at SBO is worth the investment.

[mitiempo]

You should either have a translucent tank or a tank monitor. ABYC requires there to be a way to know when the tank is 3/4 full. I would think that in some places filling it until it comes out the vent is the same as pumping out and subject to the same fines.

[Nautichthys]

Over time the inside of the poly tanks gets stained and coated, making it very hard to see through even with a six volt handheld spotlight. I keep the the tank monitor fixed and operationg but still tap the tank regularly just to make sure it's working.

If you have the same crew on a routine schedule you quickly figure out how often you need to pump. It's easier to get caught with your pants down when people are on and off your boat all the time.

The conventional float and reed switch systems that fit into the top of the tank need to be accessible as they will eventually get gummed up with toilet paper or dried crud. At this point an external capacitive sensor sounds real attractive. (Guess what I need to remove and clean next week...)

[WanderingStar]

Thanks. The tank is poly, I'll use it as is for now, add an exterior monitor later if necessary. I have been reading the head threads on the forum, as I'm also replacing hose. I don't intend to use chemicals, bacteria seems better.