Holding Tank not draining

[peghall]

Mike, his system is a bit different from the norm, but not unusual. The tank is installed entirely above the waterline with the discharge fitting IN the bottom of the tank. Dumping at sea only requires opening the thru-hull,which can just remain open while at sea...toilet flushes just pass through the tank and out the thru-hull. This type of system eliminates the need for any y-valves or pumps.



However, it can have a drawback if the discharge thru-hull has to remain closed for any length of time and/or the discharge line isn't a straight shot from the tank to the thru-hull...and sometimes even if it is: sludge fills up the discharge line, resulting in a clog. That's what kaz is dealing with.



--Peggie

[peghall]

Booboo...
Ours blocks regularly and the same on our last boat. For us the problem happens if we try to empty it when its not full enough so there is not enough weight to make enough pressure.

The simple solution: use a washdown pump or whatever works, to add water to the tank before you dump it. It's also a good idea to thoroughly rinse the bottom of the tank regularly...just add several inches of water via the deck pumpout fitting (or inspection port if you have one) 'cuz that sends the water into the tank at the bottom to stir up any sludge and hold it in suspension...and then open the thru-hull to drain the tank. Doing this while there's still only enough sludge to create very dirty water instead of thick mud will cut down on the need to auger the discharge hose. A good dose of muriatic (hydrochloric) acid in the hose will clear out any sea water mineral buildup in it. About a 12% solution left in the hose for 45 min-1 hour every few months should do it.
--Peggie

[ontherocks83]

Just out of curiosity is there any chance a guest may have flushed something down the head that wasn't supposed to be? i.e. a feminine hygiene product or other no no?

[jacktheflyer]

Originally Posted by Takamoana

Had some success with using our deckwash hose extended with a garden hose to force water back up from the hull fitting using the dinghy to get to the fitting. Be prepared for the resulting deluge if you are successful Best of luck....

This was the only method that was successful for me. The tank had a layer of hard scale which had accumulated and broken away from the bottom of the tank and repeatedly block the outlet. Acid was unsuccessful. A probe from the bottom couldn't negotiate the bend in the outlet. The top was inaccessible. After clearing the tank half a dozen times with this method I finally removed the tank and gave it a good clean. When I saw the build up of scale that was in there it was evident this was never going to clear by itself. Haven't had an issue with the second tank yet but am now using an anaerobic bacteria which claims to soften and dissolve hard deposits.
Scrubby

[ontherocks83]

Originally Posted by jacktheflyer

but am now using an anaerobic bacteria which claims to soften and dissolve hard deposits.
Scrubby

Do you have a product name or other description of what you are using?

[jacktheflyer]

Originally Posted by ontherocks83

Do you have a product name or other description of what you are using?

The stuff I use is 'ProPower' probiotic tank treatment. It has largely eliminated the foul odours that emanate from the tank breathers so I am thinking it does what it advertises. There are a number of tank treatments you can use as I'm sure you know and I don't know enough to make a recommendation other than the chemical treatments don't really work.
Scrubby

[KeithB]

We have the same set up and wondered why the previous owner left a couple of bouncy rubber balls on board.
Simples - if tank is blocked push the rubber ball hard agsonst the breather hole pn the outside of the hull, just below the rub rail. Pump the toilet hard to build up pressue in the tank and with any luck the blockage is forced out.
It worked with a manual toilet but haven't had to try it since we converted to electric.

[ontherocks83]

Originally Posted by KeithB

We have the same set up and wondered why the previous owner left a couple of bouncy rubber balls on board.
Simples - if tank is blocked push the rubber ball hard agsonst the breather hole pn the outside of the hull, just below the rub rail. Pump the toilet hard to build up pressue in the tank and with any luck the blockage is forced out.
It worked with a manual toilet but haven't had to try it since we converted to electric.

I know I am being inflammatory so take it as such, but if there is a weak point in your plumbing, just imagine what a pressurized holding tank will do when the weak point lets go. Now that would be entertaining.

[kas_1611]

Originally Posted by ontherocks83

Just out of curiosity is there any chance a guest may have flushed something down the head that wasn't supposed to be? i.e. a feminine hygiene product or other no no?

Good question but a definite NO on that one. Nothing goes through the pipes that hasn't been through our pipes and that includes toilet paper. Nappy bags are a great invention.

[NYSail]

What about a hose on the underwater fitting.... blasting up should clear it I would think.....

Good luck

[kas_1611]

Originally Posted by NYSail

What about a hose on the underwater fitting.... blasting up should clear it I would think.....

Good luck

If you don't mind filling your marina or town harbour with **** then yes probably but I for one do not want to pollute a quiet bay or harbour.

[Kenomac]

Pump it out through the deck fitting then give your boat clear water enemas till clear. Treat the low end blockage and watch what you eat.

Switching your head to a Jabsco electric macerating type will solve your ongoing issue and you won’t need to bag the TP... yuck.

[1paulg]

You can get a commercial product called a drain unblocker which is essentially a flexible cable with a shaped head on it - they are really handy for shoving up the outside exit although depending on the curves your line goes through may struggle but overall are great for this . If you get one stiff enough and have a good access to the holding tank it is possible to get it into the outlet from the inside of the tank although the fuller it is the harder it will be.
I carry one on board always !

[captain465]

Originally Posted by peghall

From your description, I'm guessing that your tank is entirely above the waterline and so it gravity drains through a fitting IN the bottom of the tank. If so, you've just learned the hard way that sludge can build up in the discharge line and pack it solidly if the thru-hull isn't opened fairly frequently to get rid of it and rinse out that line.

There are a couple of products sold here in the US that might work, but have no idea whether they're available in the UK...and they'd take quite a while diluted in full tank if they did work. So about all I can offer is an off-the-wall suggestion--IF it's even possible (I don't think you have any choice but to ignore legality in this circumstance):

If you can dive on the thru-hull with a stick in your hand (broom handles are typically 1" diameter, which should be small enough to stick into the thru-hull), have someone else inside the boat at the ready to open the seacock so you can jab in it into the hose. May require several pokes. Once it's clear, put a few gallons of water into the tank via the deck pumpout fitting--'cuz that sends the water into the tank at the bottom to stir up any remaining sludge and hold it in suspension so it will drain out of the tank.

As I said, that's definitely "off the wall" but I can't think of any other way to clear the drain line from outside of the tank.

And in the future, regularly rinse out the tank using the method I describe to prevent this happening again.

--Peggie

Peggy, could you reccomend a product that would remove the material that sticks to the insides of a poly tank? It is becoming difficult to view the tank level due to "stuff" sticking to the tank walls.

[GordMay]

Originally Posted by Pollux

I've heard someone using an air-horn (the handheld type with a compressed air bottle), holding it to the seacock. The pressure from the air, and the vibrations might work wonders.

Ingenious!