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Old 07-30-2021, 10:42 AM   #1
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Holding tank crud

Good morning :-)

Sorry for the gross subject matter... But I'm not sure how to describe this stuff at the bottom of our holding tank but it's some sort of fairly hard crud about 2" thick. How can you get rid of this crud?

Long story short, the holding tank was left full for about 4 years. We were able to pump out this week about 80% of the tank. We went in this morning through a small sensor opening with a wood stick to measure what was in there. It's about 2" of crusty crud at the bottom and maybe 3" of wet soft mud type sludge over it. Right now, we put another 10" of water over it. Tank is about 24" deep and is made out of fiberglass (about 60 gallons). We're going for a ride tomorrow and hope that the water slushing in a half full tank will help dissolve some of it but I doubt it will get the harder crud out. We also put several doses of Aqua-Kem Toss-Ins hoping it would help liquify waste.

Thanks for your help
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Old 07-30-2021, 11:16 AM   #2
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A half full tank of water sloshing around in the tank won't accomplish much 'cuz what little sludge you stir up will just settle to the bottom again....and the Aqua-Kem won't accomplish anything.

Try this instead: at the pumpout dock put enough water into the tank via the deck pumpout fitting 'cuz that sends the water into the tank at the bottom to stir up the sludge and hold it in suspension so it can be pumped out. Pump that out and repeat till you've removed all the sludge. If there's a layer of "concrete" under the sludge that this method doesn't remove, you may be stuck with it 'cuz I don't know of anything that can dissolve it that won't also damage the tank or the plumbing.

--Peggie
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Old 07-30-2021, 11:21 AM   #3
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Some members have used Noflex to help break up the hard stuff. No idea if it will help or not but maybe worth a shot.
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Old 07-30-2021, 11:27 AM   #4
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A half full tank of water sloshing around in the tank won't accomplish much 'cuz what little sludge you stir up will just settle to the bottom again....and the Aqua-Kem won't accomplish anything.

Try this instead: at the pumpout dock put enough water into the tank via the deck pumpout fitting 'cuz that sends the water into the tank at the bottom to stir up the sludge and hold it in suspension so it can be pumped out. Pump that out and repeat till you've removed all the sludge. If there's a layer of "concrete" under the sludge that this method doesn't remove, you may be stuck with it 'cuz I don't know of anything that can dissolve it that won't also damage the tank or the plumbing.

--Peggie
Thank you Peggie for the tips. Can you describe what you mean by "concrete" ? I'm able to break appart with a wood stick that crud stuff so it's not as hard as concrete but it seems to be coming off in pieces. Is that what you describe as concrete or is it really something that I wouldn't be able to break appart with a small wood stick?
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Old 07-30-2021, 11:29 AM   #5
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Maybe dumping some very hot water down the deck fill after emptying the tank as much as possible?
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Old 07-30-2021, 11:30 AM   #6
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You may be able to use that stick to break up the crud and then pump it out.

Or, get yourself an access fitting six to eight inches in diameter, cut a hole in the top of the tank to fit the fitting, clean out the tank with whatever works (probably a scraper with a long handle), rinse it well and then install the access fitting.

And yes, I have done exactly what I described.
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Old 07-30-2021, 11:41 AM   #7
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If you can break them up small enough maybe a shop vac will suck them out. Then buy a new shop vacÖ
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Old 07-30-2021, 12:30 PM   #8
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Previous posting:

https://www.trawlerforum.com/forums/...way-46357.html

If you have that level of solids then your tank pump suction is probably plugged. Cleaning will take multiple fill and pump out sessions. Unless you have easy access to a pump out station one way is to get largish diaphragm pump and pump from the top. I have used a Whale Gusher Urchin Manual Bilge Pump with a 1 1/2Ē corrugated suction hose and garden hose discharge. This was through a 4Ē top fitting. Also used a garden hose with a jet stream nozzle for agitation.

As you can imagine this could be messy but if you think it through, have rags and buckets, leak checked fittings, and plastic sheeting it works. Our tank is under our bunk and I have done it several times without spillage.
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Old 07-30-2021, 01:12 PM   #9
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I'm a user / believer of NoFlex or the generic equivalent sodium percarbonate available in bulk.
I have also periodically (end of season) used Calgon water softener and believe it helped but it seems more difficult to find in stores recently.
If you have access a pressure washer or garden hose w straight nozzle help break things up so repeated pump outs clean it up.
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Old 07-30-2021, 01:48 PM   #10
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If you break up hard chunks and try to pump out right away you may clog the pump out line. Break it up and let it soften. It would probably be better to take big chunks out whole.
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Old 07-30-2021, 02:11 PM   #11
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Quote:
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If you break up hard chunks and try to pump out right away you may clog the pump out line. Break it up and let it soften. It would probably be better to take big chunks out whole.


Thatís what I was worried about. Clogging the pumpout pickup tube/hose with large chunks. Iíll let it soak/pump/repeat for a while and see if it gets better. If not, Iíll have to make a hole on the top of the tank and clean it the hard way. Itís fairly easy with fiberglass tank and I have very good access to the top of the tank.
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Old 07-30-2021, 02:30 PM   #12
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If you have that level of solids then your tank pump suction is probably plugged

He said in his first post that he'd been able to pump out about 80% of the tank contents...that would not have been possible if either the tank discharge outlet or the tank vent were blocked.

There should be no chunks of any size in any sludge that can be stirred up and held in suspension using a hose with a nozzle on it to generate some pressure down the pumpout line.

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Old 07-30-2021, 03:11 PM   #13
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Quote:
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Thatís what I was worried about. Clogging the pumpout pickup tube/hose with large chunks. Iíll let it soak/pump/repeat for a while and see if it gets better. If not, Iíll have to make a hole on the top of the tank and clean it the hard way. Itís fairly easy with fiberglass tank and I have very good access to the top of the tank.
I'd buy 10 - 20 lbs of sodium per carbonate. Its about $3.50 per pound in bulk. Take a cup or two partially dissolved in a gallon of hot water poured down the extraction port. Follow with another couple gallons of hot water and maybe some laundry detergent as well. Repeat until successful. Then used the balance to keep it nice. A little down the toilet daily works for us. NoFlex is 80% sodium per carbonate.
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Old 07-30-2021, 03:33 PM   #14
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Another one here for Noflex Digester.........
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Noflex__77968.1610389527.jpg  
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Old 07-30-2021, 03:36 PM   #15
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I think the key is what Peggie recommended at the beginning. When you pump out, make it a habit of flushing the tank with fresh water.

I have gotten lazy recently and will have a pump-out boat pump my tank fairly frequently. However, I make sure I do it myself periodically so I can flush the tank well. I pump out the tank, then using a hose, fill up the tank via the pump out fitting, then pump out again, and repeat until what I pump out is essentially clear. That short length of clear pipe in the pump out hose is very handy. It will take several times of doing to to get it pretty clear. I try to make sure I do this at a time when the pump-out doesnít have any boats waiting.

BTW, another suggestion is to back flush your holding tank vent when you pump out. This helps keep the vent line free. I just direct a stream of water to the vent opening as Iím pumping the tank. You only need to get enough water through the vent line to flush it.

No-flex or sodium percarbonate used regularly over time may help with any remaining deposits but once you get the sludge out, any remaining deposits arenít likely to be an issue.

If you have good venting of the tank, you can get Peggieís thoughts on using K.O rather than the sodium percarbonate.
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Old 07-30-2021, 03:58 PM   #16
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Good morning :-)

Sorry for the gross subject matter... But I'm not sure how to describe this stuff at the bottom of our holding tank but it's some sort of fairly hard crud about 2" thick. How can you get rid of this crud?

Long story short, the holding tank was left full for about 4 years. We were able to pump out this week about 80% of the tank. We went in this morning through a small sensor opening with a wood stick to measure what was in there. It's about 2" of crusty crud at the bottom and maybe 3" of wet soft mud type sludge over it. Right now, we put another 10" of water over it. Tank is about 24" deep and is made out of fiberglass (about 60 gallons). We're going for a ride tomorrow and hope that the water slushing in a half full tank will help dissolve some of it but I doubt it will get the harder crud out. We also put several doses of Aqua-Kem Toss-Ins hoping it would help liquify waste.

Thanks for your help



I have a hose with a tip on it that is made for jetting sewer lines. you can get a rotary tip or just a straight tip. At work we have problems with some stuff called iron bacteria that make a sludge that clogs up our fresh waterlines from our well. We use this hooked to our pressure washer and it cleans them right up. the Hose it is about 3/8s of an inch you would be able to put it in the tank hooked to a small electric pressure washer will you are pumping out and that should help fix you right up.
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Old 07-30-2021, 04:17 PM   #17
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I think we've already decided that any solution will be gross, so how about this? A plumbing snake. As long as there is no float sensor or anything for it to catch on, it can only work through crud. It's a blind approach as there is no way to actually direct the end once it is in the tank, but maybe with enough penetrations it would loosen up the crud.

They make basic ones that are inexpensive.
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Old 07-30-2021, 05:16 PM   #18
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You may also want to check out RV supply places like Campers World. They sell long plastic tubes that attach to a hose to go deep into holding tanks to mix things around.
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Old 07-30-2021, 05:40 PM   #19
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the snake will be hard to control in the tank and i would be worried about being too aggressive and doing more damage.


this is just one example of the tip i was talking about



https://www.amazon.com/XZT-3000psi-R...93244242&psc=1



http://https://www.amazon.com/Rotati...8NQ1444P&psc=1


Quote:
Originally Posted by Marco Flamingo View Post
I think we've already decided that any solution will be gross, so how about this? A plumbing snake. As long as there is no float sensor or anything for it to catch on, it can only work through crud. It's a blind approach as there is no way to actually direct the end once it is in the tank, but maybe with enough penetrations it would loosen up the crud.

They make basic ones that are inexpensive.
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Old 07-30-2021, 05:53 PM   #20
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In dairy manure tanks, the pump can either pump out or operate a nozzle near the tank bottom. It breaks down solids and gets them back in suspension. Ideally a round tank, but it will get most of the corners on a rectangular tank. They way it's plumbed the nozzle can turn about 180į.
The longer manure sits in a tank, the more it compresses. A full tank is putting all its weight on the stuff at the bottom, compressing the liquid out of the sludge, compacting it.
One of the main reasons I have Incinolet toilets. Id never have a marine toilet again after having Incinolets. My oldest is 10 years old, daily use, no failures, no holding tank, no brown fingers.
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