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Old 22-12-2013, 09:53   #1
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De-sludging holding tanks ? Advice ?

The boat is new to me and has been in storage for the past 3 years.

I think the holding tanks are all gummed up with sludge.

Symptoms are -

- Tank indicators have failed on both.

- After numerous flushings and pump outs - the water being extracted by the pump out system is "crystal" clear with no solids being extracted.

- One tank with rated capacity of 30 gallons appears to hold only about 10 gallons - it overflows fairly rapidly when being filled by a hose through the deck fitting.

- Tanks are aluminum and seem to be in good condition, boat is 6 years old but has not been used much at all. Yes, yes yes... I know that metal tanks are a big No No... but I'm stuck with it until it fails.


I really, really don't want to remove the tank and open it up for cleaning.

Is there any magic chemical which I can add to the tank to de-sludge it and wont dissolve the aluminum tanks?

I have been trying nitrates with not much joy so far. Not sure how long they take to work.

Any Advice to cheer me up for Christmas?
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Old 22-12-2013, 10:36   #2
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Re: De-sludging holding tanks? Advice?

Take her out in rough water with the tanks half filled with water? Works for RV's, may work on a boat.
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Old 22-12-2013, 10:55   #3
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Re: De-sludging holding tanks? Advice?

One method, if possible, pass a semi flexible piece of plastic pipe down into the tank and blow a good volume of compressed air down the line at the same time twisting the pipe back and forward, generally trying to move it around in the tank bottom to agitate any sludge and pumping away any waste matter. Alternatively some pressure washer suppliers sell a retro jet for a few bucks for cleaning drains, these can also be very effective. Followed by a session as suggested by a64pilot.
Good luck.
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Old 22-12-2013, 11:45   #4
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Take her out and fill the tanks half way with ice. I did this in my Rv and it works very well.
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Old 22-12-2013, 13:03   #5
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Re: De-sludging holding tanks? Advice?

We did the rough passage thing - although without intending to. Nothing loosened up in the holding tanks. Although the potable water tanks released huge amounts of gunge which closely resembled the stuff they wrap sushi with - and tasted as bad. Nori? I think they call it.

After Xmas, I'll take Irish Ramblers advice and see if I can source a pressure washer accessory to poke down the deck pump out fitting and see if I can loosen things up.

But would have preferred a passive solution using a chemical or bacterial agent to do the work for me.
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Old 22-12-2013, 13:12   #6
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Re: De-sludging holding tanks? Advice?

It sounds like your problem is well beyond the usual holding tank challenge.

I'd contact these guys (or someone like them) to see if this is safe with aluminum.

Septic Shock - Instant Power Septic System Treatment
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Old 22-12-2013, 13:39   #7
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Re: De-sludging holding tanks? Advice?

Make sure that Septic Shock wont harm the aluminum tank. If it is unsafe then use Calgon and some HE laundry detergent. Let it work in the tank for a week and then try the power wash. To be sure the tank holds what you think it should be easy enough to estimate the measurements to work out the volume.
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Old 22-12-2013, 13:39   #8
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Re: De-sludging holding tanks? Advice?

Not sure what it is called, but there is a brass thing about 3/4" around the looks like a bullet and has holes that water discharge from the face rearward. It's put on a pressure washer hose and it's used to unclog sewer pipes, the water jets push the thing forward and of course the high pressure water breaks up any sludge, you can rent thewhole thing at a tool rental place.
I think the ice thing is an excellent idea as well, you get the chunks of ice to work like like gravel to bust things up, but of course since ice melts, you don't have to deal with removing gravel
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Old 22-12-2013, 13:47   #9
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Re: De-sludging holding tanks? Advice?

Quote:
Originally Posted by neelie View Post
Any Advice to cheer me up for Christmas?
Yes, leave it well alone until after Christmas. The memory of exploding pooh tanks won't make for a good day on the 25th.


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Old 22-12-2013, 13:53   #10
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Re: De-sludging holding tanks? Advice?

Neelie,

Be careful what you use to clean the tanks. High pH detergent cleaners can cause corrosion and pitting of the aluminum. If you use such products, make sure not to let them sit in the tanks; rinse thouroughly.
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Old 22-12-2013, 14:12   #11
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Re: De-sludging holding tanks? Advice?

Thanks all...

I just read through the Septic Shock website - I think this may be the ticket!. Thanks for the tip. Looks like they have some sort of poo munching enzyme. I just need to ensure the byproducts are not corrosive.

Hud,... I have so far resisted using strong reagents in the Al tanks. Just nitrates which are meant to "feed" the bacteria. It seems my bacteria are somewhat anorexic - they're not doing much munching.

Forgot to mention that I am presently in South Florida - the ice cube solution will be too much of a challenge.

Anyhow, thanks everyone for your advice. I will try all the suggestions.

Wishing you all a very Merry Christmas.
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Old 22-12-2013, 14:56   #12
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Re: De-sludging holding tanks? Advice?

I am a motorhoming wannabe sailor and follow several motorhome forums. There was a lengthy discussion about what is called variously the "black mountain" or "pooh pyramid" in black water tanks last August. Some good information in there that I think will be helpful.
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Old 22-12-2013, 15:29   #13
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Re: De-sludging holding tanks? Advice?

The bacterial cultures sold by hardware stores to clean septic tanks and leech lines worked great for our holding tanks.
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Old 22-12-2013, 15:42   #14
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Re: De-sludging holding tanks? Advice?

I assume your problem is dry up human waste totally cake the surface of the tank. Use detergent with OxiClean to re-hydrate the solid matter and then pump it out. I guess you may need to have to soak for a week or so.

Alternatively is to use a sand blaster to blast as much as you can, fill with H2O and vacuum it out, repeat unit clean.

Good luck.
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Old 22-12-2013, 16:41   #15
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Re: De-sludging holding tanks ? Advice ?

Just went through the same. I have an integral fiberglass tank on a 1989 that has never been cleaned. I filled it with a few gallons of vinegar and beat 1800 miles from Florida to the Caribbean. Opened the top when I arrived and the tank was literally spotless. Not sure what distance you need but a good vinegar soak and a solid beat will do the trick.
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