Holding Tank Cleaning, the Easy Way

[timb7734]

Steel holding tank

This boat was built in 1998, so it’s 20 years old, tank is 250 gallons as designed and part of the steel hull, as are the fuel, water, and grey water. Last year we epoxied the water tanks with a food grade paint. No evidence of either odor or leaks.

 

[ranger58sb]

FWIW, Dave says his NoFlex Digestor will clean a tank so the sidewalls are clean like that end result.

We replaced our original tank with new, so the old one is outside our house just now... looking much like your starting situation. I'm tempted to experiment with NoFlex, but evacuation of the tank would be sort of a pain so I haven't been quick to jump into that kind of test.

I originally thought about trying to clean the tank with NoFlex and Tide. Based on the cost and recommended volume, I decided to try the Sodium Percarbonate first.

While I was aware of NoFlex, had acquired it and used it as directed, I found no evidence after 2 years that it was cleaning my tank walls. It may perform in the same way as my concoction with a tank full of water, but I think a tank full of poop would probably over power it, at least for a remediation process. Anyway, at the time and since, I haven't seen any documents suggesting to use it as I used my concoction.

I finally got off my... er... duff... and began to address our old take-out tank. There was enough "leftover" in there that sunlight was beginning to cause too much of a methane (I think?) build-up, a little tank bulge, etc. Once I could vent that in cooler morning temps, at least the bulge went away...

But there's also some sludge on what was the bottom, and what is now the new bottom since it's been stored in a different, more upright, position.

First was to empty the thing into the outside sewer clean-out at our house; not too hard. Then some hose water to move at least some of the sludge off the old and new bottom... followed by another empty... rinse and repeat a number of times...

There was about a 2" layer of sludge covering the original bottom... enough so I could hear the whole mess sliding toward the drain fitting as I tipped the tank.... and this is after several (4? 5?) years of daily NoFlex treatment when we're aboard.

Given we confirmed our discharge hose from toilet to holding tank has a belly in it, and it's about 10' in length... I think what's been happening is that our NoFlex treatment, applied by flushing through the toilet, just doesn't really get to the tank -- unless we flush enough water to force it all the way through that hose. Possibly the 2" of sludge in the old tank confirms that. Flushing that much water wouldn't be such a great way to conserve holding tank volume, so I suspect it'll be better if we add NoFlex or whatever from the pump-out fitting, with maybe just a tad of water to get it all the way down into the tank.

The tank will clean up; think I'll probably first just pour some Oxyclean down in there and see if that's good enough. I don't need it pristine, given I'll probably just offer it up to anyone who needs a tank... but experimenting with the various cheap cleaning stuff (OxyClean, Tide, sodium percarbonate, etc.) a little bit at a time may be instructive.

-Chris

 

[firehoser75]

Check Duckbills??

Ted,
Did you get around to having a look for any adverse reaction on the duckbills (or other components) from using your "concoction"?

Thanks,
Tom

 

[O C Diver]

Boat is on the hard now. Busy with annual maintenance and a number of change orders. Hopefully this week I'll be doing sanitation maintenance (can't believe I wrote that).

Ted

 

[slowgoesit]

I occasionally added the GEO mixture for mental OCD supression(about once a month). I started doing this on a Watkins 33 I owned and now on my newest aquistion of the Trawler variety.

Actually, it's CDO, not OCD. Same meaning, but the letters are in correct alphabetical order.

 

[RickyD]

I'm amazed that your holding tank is metal 'cuz urine will turn any metal tank, even 316 stainless, into a colander in an average of about 10 years. Exceptionally thick walls and/or coating the interior of the tank with epoxy will add a few years, but as epoxy ages it develops cracks that expose the metal to the tank contents and even inch thick walls will start to leak sooner or later.

It won't be a catastrophic failure...you'll start to experience odor from the compartment where the tank is--a leak, typically at a weld at a seam or a fitting. You may be able to patch it with something like JB Weld, but that's the time to start planning to replace it with a top quality plastic tank...'cuz the first leak in any metal holding tank is ONLY the FIRST leak. (I once knew a houseboat owner who'd patched his aluminum holding tank with JB Weld in so many places it was close to turning into a tank made entirely of JB Weld!)

To answer your question though...a combination of sodium percarbonate and detergent shouldn't do any harm to the tank.

--Peggie

We all know that there are exceptions to every rule. I was concerned about my aluminum holding tank. It is now 30 years old and still holding. I hope that by writing this I haven't jinxed the situation and tomorrow it will start leaking. Me and my big keyboard.

 

[FF]

If the tank top can be accessed the RV solution to "standing soldiers" might be simplest.


Empty the tank , feed in 20+ lbs of ice cubes and go for a ride.

 

[Chuck in WA]

I know this is an older thread, but I just have to say THANK YOU to Ted for posting it! I completed "The Ted Treatment" early this summer, and was amazed at how quickly it worked. In my case, my goal wasn't to necessarily clean the tank walls (I can't even see the tank), but rather to get rid of the God-awful smell that came out of the vent after flushing, a problem I've been putting up with for a few years. My vent is located near the bow of the boat, and of course we (and our guests) relax on the aft sundeck. 99% of our time is spent on a mooring or at anchor vs. dockside, so of course we're always sitting downwind of the vent. It got to the point where my wife was so embarrassed by the smell, she would make everyone walk up to the bow of the boat and, once in position, she would go and make the flush. Then she'd circle the sundeck, give the "all clear", and only then could we go back and sit down, lol.
I didn't use nearly the volume of "concoction" that Ted did, but I mixed it in the same way. I added maybe 10 gallons of the stuff through the pumpout port to my empty tank. I let it sit for about 2 weeks while I was away, and I was shocked to find the flush smell completely gone the next time I returned to the boat! I hadn't even pumped the remaining slurry out yet! Since then, I add about a Tbs of the Sodium Percarbonate down the Vaccuflush each day we use the boat, and so far this summer - no smell at all! I mean NO smell! I'm amazed (and thankful).
As I ordered 25 pounds of the SP, I have a lot leftover. I recently purchased a bulk pack of 1 pint Rubbermaid containers with a spout. I keep one in each bathroom filled with the SP, and have started giving the others away as gifts to boating friends, lol.

 

[O C Diver]

Glad to hear you had success with it. Will be cleaning mine and replacing the duck bill valves later this month. Will be reducing the amount of chemicals by 75% to see how little I can use.

Ted

 

[catalinajack]

The active ingredient in NoFlex Digestor.

I know this is an older thread, but I just have to say THANK YOU to Ted for posting it! I completed "The Ted Treatment" early this summer, and was amazed at how quickly it worked. In my case, my goal wasn't to necessarily clean the tank walls (I can't even see the tank), but rather to get rid of the God-awful smell that came out of the vent after flushing, a problem I've been putting up with for a few years. My vent is located near the bow of the boat, and of course we (and our guests) relax on the aft sundeck. 99% of our time is spent on a mooring or at anchor vs. dockside, so of course we're always sitting downwind of the vent. It got to the point where my wife was so embarrassed by the smell, she would make everyone walk up to the bow of the boat and, once in position, she would go and make the flush. Then she'd circle the sundeck, give the "all clear", and only then could we go back and sit down, lol.
I didn't use nearly the volume of "concoction" that Ted did, but I mixed it in the same way. I added maybe 10 gallons of the stuff through the pumpout port to my empty tank. I let it sit for about 2 weeks while I was away, and I was shocked to find the flush smell completely gone the next time I returned to the boat! I hadn't even pumped the remaining slurry out yet! Since then, I add about a Tbs of the Sodium Percarbonate down the Vaccuflush each day we use the boat, and so far this summer - no smell at all! I mean NO smell! I'm amazed (and thankful).
As I ordered 25 pounds of the SP, I have a lot leftover. I recently purchased a bulk pack of 1 pint Rubbermaid containers with a spout. I keep one in each bathroom filled with the SP, and have started giving the others away as gifts to boating friends, lol.

 

[O C Diver]

An Update:

It was time to head to the boatyard and annual service on the head systems. There weren't many trips this summer and August was spent rebuilding the steering system. The holding tank hadn't been pumped since July. So I pump the tank and refilled it with freshwater followed by another pumpout. Did this a couple more times till the pumpout water was clear.

Hears what the tank looked like:


The plan was to reduce the amount of SP and Tide and hopefully still clean the tank. I decided to mix the same batch ratios but eventually top the tank with fresh water. Mixed 2 batches and ran one into each head. Waited 2 days. Mixed 2 more batches and ran them into each head and waited 2 more days. Then kept flushing buckets of warm water into each head until the tank was full. Waited 5 days and pumped out the holding tank several times with freshwater refills in between.

Here are the results:


The ratio of cleaning concoction in the tank went down to between 20 and 25%. Was mostly happy with the results. More time may have been better, a higher percentage may have done more. Going for a beam roll in seas before pumping out might also help.

How this effected the Vacuflush:

It's been 5 years since I replaced the vacuum pump accordion plungers. I decided my maintenance schedule would be to replace them every 5 years and the duck bill valves annually. I decided last year to change one pump's valves and let the other ride another year to see if there was any noticeable increase in deterioration from the SP and Tide.

The cleaning solution works perfectly in prepping for the rebuild. No residue or smell anywhere in the system. The valves were indistinguishable from each other and almost like new. Imo, the SP and Tide seem to have no effect on them based on the exposure time. The plunger and orings were also unaffected.

Had some amount of Struvite in parts of the pump from some water conservation while in Lake Superior in 2017. Soaking the plastic parts in white vinegar overnight desolved all but the bottom of the pump housing. 20 minutes of muriatic acid cleaned the housing nicely. Both pumps rebuilt nicely and other than valve changes, should be good for another 5 years.

Ted

 

[RickyD]

I'm amazed that your holding tank is metal 'cuz urine will turn any metal tank, even 316 stainless, into a colander in an average of about 10 years. Exceptionally thick walls and/or coating the interior of the tank with epoxy will add a few years, but as epoxy ages it develops cracks that expose the metal to the tank contents and even inch thick walls will start to leak sooner or later.

It won't be a catastrophic failure...you'll start to experience odor from the compartment where the tank is--a leak, typically at a weld at a seam or a fitting. You may be able to patch it with something like JB Weld, but that's the time to start planning to replace it with a top quality plastic tank...'cuz the first leak in any metal holding tank is ONLY the FIRST leak. (I once knew a houseboat owner who'd patched his aluminum holding tank with JB Weld in so many places it was close to turning into a tank made entirely of JB Weld!)

To answer your question though...a combination of sodium percarbonate and detergent shouldn't do any harm to the tank.

--Peggie

I guess I'm really lucky. The 80 gal forward holding tank on my boat was built in 1991. It is thick aluminum and still holding. Conversely the aft aluminum holding tank was replaced with plastic before I bought the boat in 2018. I know it is just a matter of time but so far so good.