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E30+, how do you tell when the holding tank is full?

light24bulbs

E30+ 1984, San Juan Island, Wa
I made the mistake of using the toilet one too many times and had some effluent come out of the air vent. Not a disaster but not great.

The tank is super black, the hoses are super opaque, and I can't figure out how to check the level. Am I missing something obvious? This is my first boat big enough to have a holding tank. The tank is on the port side under the V birth bunk.

They're overpriced and require me to run power, but I do see some external meters designed to stick on the side. I guess they're capacitive. I'd really rather keep an eye on the level than not know.
 

Frank Langer

1984 Ericson 30+, Nanaimo, BC
Hi,
Other than the external meters that one can put on the side of the holding tank, I'm not aware of any other way to monitor the level. Our holding tank holds 15 gallons, and after many years of owning our boat, I know how long I can go before emptying the tank, depending on how many people are on board. When my wife and I are on board during a cruise we empty the holding tank daily to avoid problems.
In your case, ensure that the air vent is now clean and not plugged with any residue, as that can also cause other problems.
Frank
 

driftless

Member III
Blogs Author
I installed one of the external meters. Fairly easy to install, and works very well. The calibration process is a bit convoluted. They're low power so wiring isn't too burdensome. But my holding tank is in the cockpit locker, so a shorter run to power. For me it was worth the price of knowing.
 

peaman

Sustaining Member
Reliable level monitoring of black water is more challenging than other usual fluids, but there is one system I installed several years ago which is pretty interesting. Hart Systems "Tank Tender" has a monitoring panel with a precision pressure gauge, a tiny manually operated air pump, and buttons to select which tank to check (it can serve multiple tanks). A small vinyl hose runs from the monitor panel to the top of each tank and connects to a small nylon (?) tube which extends down into the fluid to be be measured. To check the fluid level, the small pump on the panel is operated, which sends air through the tubing into the tank until bubbles escape. The pressure gauge can then be read, which will indicate the number of inches of fluid in the tank. The system is super simple, non-electric, and as reliable as one could want.

I don't know about availability or cost, as it was some time since I installed and used that system, but I wanted to share it, since it is about as good as it gets for measuring black water.
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
If possible, empty the tank before the question of level comes up. Effluent "held" has few pluses. I know that's easier said than done in some locations, but it's essential not to leave stuff in the holding tank for weeks or months. Not designed for that.
 

G Kiba

Sustaining Member
I have an older version of the SCAD system and it works great. Power is only applied when checking the level by pressing a button.
Wish I had the two tank version. It would be nice to know the level of the fresh water tank as well.
 

paul culver

Member III
I suppose you could DIY a sight tube on the outside of the tank, but it might get clogged. Dip stick would work but who wants to check it? One great advantage of a flexible bladder holding tank -- you can tell how full it is by looking at it.

It helps to have a Plan B for dealing with waste when the system fails. Trash can liners.
 

william.haas

1990 Ericson 28-2
This will not help you with your current setup but tuck the idea away for the future. When I rebuilt my entire marine sanitation system I also replaced the holding tank (the project is a blog post I never got around to finishing). I purchased the exact same tank from Ronco, except that I specified an opaque white color as opposed to the black. This way I can slide the cover/panel slightly off, hold a flashlight against the tank, and see the fluid level.

I also strongly agree with @Christian Williams comment - holding tanks are just that and not storage tanks. While timing may not allow for a pump out after every evening sail on a school night, we try to pump out as frequently as possible.
 
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