Battery and waste tank monitors

Got the new monitors installed as well as the "stinky" sensor. The new sensor works good and I verified operation with a bucket of water before I installed it. Because (you know) the less time you spend around an open poop tank the better -



The battery monitor went in where the old tank monitor (full light only) existed. Needed to open up the hole a little and will build a little frame around it to hide the discoloration caused by the old flange. The tank monitor was much easier, just popped it in the vent hole and trimmed the vent to match.

I need to instruct the marina to pump the tank empty. I think they missed a previous request and I found the tank full before I started the sensor replacement. I mean full as when I patted the top it was like patting the side of a doughboy pool. So they pumped it, but when I removed the float switch I saw the brown water an inch and a half from the top of a 13 inch deep tank. Which is good enough to put the sensor in but not for the bubbler. I think maybe they are afraid of imploding tanks? I used to know when they pumped it as the water would be gone in the toilets. The 2 Marine Elegance heads will easily pull air through the duck bills, so the tank is never in danger of crushing. Need to explain this to them so they can put a good hard suck on the tank -

Anyway, I set the "full" calibration to where it is now, but I have room for about 5 more gallons which is good to know as it takes about a week for them to do after you file the pump request.

You installed the tank level sensor in the holding tank vent thru-hull??? There's no way that enough air can be pulled in through any toilet to prevent the pumpout from pulling a vacuum that'll prevent it from pulling out more than gallon or two! And just as bad if not worse, if air displaced by incoming waste can't escape through the vent, the tank will become pressurized, creating back pressure that not only prevents the toilet from flushing but can result in a geyser from the bowl or, if you're lucky, one out the deck pumpout fitting when the cap is removed, which can be one way to "pump out" a tank, but not one that's recommended!

Get rid of that internal tank level sensor that's supposed to be inserted through the top of the tank and buy one that uses sensors designed to attached to the outside of the tank. SCAD are top rated, reasonably priced, easy to install, and available from a number of retailers including Amazon. And also replace the "vent" thru-hull with an open bulkhead fitting that'll allow enough air exchange to provide enough oxygen to prevent odor and also let you put a hose nozzle against it to backflush the vent line often enough to prevent anything from setting up housekeeping in it.

--Peggie

No, the tank vent is still there and still works as that is what's venting the stink when we flush. Not touched during new sensor install. New sensor is rod style solid state capacitive same principal as the outside foil type, but I have no access to the sides of the tank, only the top.

That the pumpout isn't able remove but a gallon or two is a strong indication of a blocked vent. So if "I just popped it in the vent hole and trimmed the vent to match" and you're convinced that the pumpout should be able to pull enough air in through the toilet doesn't mean you put it in the vent thru-hull, where exactly DID you put it??? 'Cuz something has to be blocking the vent, maybe not entirely but enough to cause problems.
The two most common locations for a vent blockage are the "vent" thru-hull and the other end of the vent--that end of the hose and the vent fitting on the tank. ...and anything inserted into the vent line, including a filter.
This is a problem that needs to be solved and I'll be glad to help you do it, 'cuz relying entirely on the amount of air that can be pulled in from the toilet isn't gonna work and can damage the toilet.

-Peggie

I trimmed the hole that the display fits in. The display is in the saloon.

The sensor is in the poop tank. The vent works. The vent has always worked.

Thanks for clarifying! "Vent" thru-hulls are actually designed to keep sea water out of the fueI and water tanks...they seriously restrict the amount of air exchange to and from holding tanks, but boat builders use them any way because it costs them less to use the same thing on all vents than using different one for holding tanks, and "vent" thru-hulls are the most common location for blockages. I suggest you replace the "vent" thru-hull with an open bulkhead (aka "mushroom") fitting that lets the pumpout pull in enough air to empty the tank. An open thru-hull also has another advantage: you can prevent vent blockages by putting a hose nozzle against it to backflush the vent line every time you wash the boat and/or pump out (NOT during pumpout but before or after) to send anything that's trying to set up housekeeping in it into the tank.

--Peggie

Yes, I agree!

The current vent hose is 1/2" , yeah, I know, pitiful. Also connects to top of tank with 90 degree elbow. No easy way to access the outside vents (clamshell), so I'm considering a hole saw to make a larger hole and then using a mushroom with a HDPE flange that I can screw on. The hole will allow me to poke the new hose through from the outside which is much easier than the rear of the engine room. Will require much measuring from known locations both inside and outside to find a spot where the hose can pass easily by the fuel tanks.

Delta Riverat said:

Also connects to top of tank with 90 degree elbow.

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I am approaching this same upgrade. Is it worth replacing the elbow with a tee topped with a ball valve? The benefit would be to allow entry to measure tank level with a dip stick. My SCAD sensor has been completely reliable, but a second and nearly foolproof way to validate the SCAD level sounds worth the small cost of the extra fittings.

Delta RiverRat:
How long is your vent line, how straight is it and how much does it rise?
Ideally (which is rarely possible) vent lines should be only about 5' long, straight as an arrow and not rise more sharply than 45 degrees
If yours is waay off that rule-of-thumb, a new 1" vent thru-hull closer to the tank may be the best solution. You should be able to find stainless steel bulkhead fittings.

--Peggie

HeadedToTexas said:

I am approaching this same upgrade. Is it worth replacing the elbow with a tee topped with a ball valve? The benefit would be to allow entry to measure tank level with a dip stick. My SCAD sensor has been completely reliable, but a second and nearly foolproof way to validate the SCAD level sounds worth the small cost of the extra fittings.

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It's not worth doing. USCG regs only require that there be a means of determining when the tank is 3/4 full. If the location of the tank and the tank material allow visual inspection of the tank contents level, this is acceptable. A tank level monitor is only required if visual inspection is impossible. However the convenience of knowing the contents level without the need to inspect the tank makes a tank monitor worth the expense. I'd just wait till it "breaks" before doing anything more to "fix" it than having a replacement for any part on hand.

--Peggie

HeadMistress said:

If the location of the tank and the tank material allow visual inspection of the tank contents level, this is acceptable.

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While I can see the whole aft side of my holding tank and about half of the top, the tank is fiberglass and completely opaque. The only clue I have to its volume is the display on the SCAD. Again, it has been very trustworthy but I will soon be capping the old ½" vent and installing a new 1" vent in a Uniseal. Using a tee instead an elbow and adding a ball valve to the top of the tee would be virtually free as I already have the parts.

Was out to the boat cleaning up a bit after these projects but more importantly, file another pump out request. I thanked them for the pump before as it allowed the sensor replacement but added that the tank was still 80% full and to please pump empty this time. That got her attention as another boat on my dock reported the same. She was thinking that the suction on the vacuum system might be low and going to advise the owner.