Holding Tank Cleaning, the Easy Way

[O C Diver]

If your holding tank looks like the upper part of this one



and you want it to look like this one



I have the answer.


So, my holding tank was so fouled on the inside, that I couldn't see the liquid level. What started out as a process to just be able to see the level became an obsession to get it completely clean. I read all the postings from the Head Mistress, added to her recommendation, and had an undesirable outcome (not the Head Mistress's fault). So let me explain what did and didn't work for me.

I have an 80 gallon holding tank. Generally, due to the size, 2 gallons of degreaser laundry detergent is recommend. I used 2 gallons of Purex the first time which was a mistake on my part. The second time less than a gallon of Tide (the preferred brand) was used.



Each time I used Sodium Percarbonate, 10 pounds the first time and about 8 pounds the second time. For those not familiar with Sodium Percarbonate, it's the main ingredient in Oxyclean. In a thread on the forum it was also suggested as the main ingredient in one of the popular head plumbing cleaning granular additives (not going to say any more than that). My thought was that this would dramatically improve the cleaning action of the laundry soap. 10 pounds is around $20 on ebay. This was not recommended by the Head Mistress.



To the soap and Sodium Percarbonate you add water and agitate the tank. This is where my first attempt about a year ago went really badly. I flushed the tank out well with fresh water. Then with 150 degree hot water (we all know hot water can accelerate chemical reactions), I poured the 10 pounds of Sodium Percarbonate into the pumpout port for my holding tank (basically a slurry). Next was the 2 gallons of Purex. Finally, I emptied the remainder of my 20 gallon hot water tank into the holding tank and put the cap back on the pumpout port. The plan was to go outside the harbor, roll in the troughs of 2' seas to agitate the concoction until the water heater was ready to add another 20 gallons of water to the holding tank. About a half hour later when the water was hot, I removed the cap for the pumpout port and was greeted with a brown foamy outflow. I won't bore you with the remediation and cleanup processes. Lets just say I returned to the pumpout dock unobserved, emptied the tank and cleaned up the boat.

Incident analysis (it's only an accident if you get caught) determined that the Sodium Percarbonate doesn't dissolve instantly (especially when sitting in a pile in the bottom of the holding tank. Too much of the wrong kind of soap without enough water makes an incredible amount of foam. Hot water really enhances chemical reactions. Apparently rolling a boat is a great way to dissolve the Sodium Percarbonate and trigger one hell of a chemical reaction. The final insult was that the chemical reaction worked, freed some solids, which floated on the foam, eventually plugging the holding tank vent.

You might think after this experience that I would concede defeat and leave well enough alone. Time heals all wounds and egos.

Version 2.0
This time I decided to approach the task in a more restrained manner. I procured another 10 pounds of Sodium Percabonate, a 1.2 gallon jug of Tide and dialed the water temperature back to 100 degrees. This time I mixed batches of cleaning solution. In a 6 gallon bucket I dissolved about 6 ounces (by volume) of Sodium Percabonate in 4 gallons of hot water. It took a couple of minutes of stirring with my hand before there were no granules left on the bottom. Then I added about 5 ounces of Tide which mixed instantly. After waiting several minutes on the first batch to check for adverse reactions, I filled the bowl of my Vacuflush toilet and flushed it. It actually took 2 rounds to flush the 4 gallons into the system. I rinsed the bowl with a little fresh water and repeated the process on the second toilet. After waiting 2 days, I flushed about 10 gallons of fresh water through each toilet, and went to the pumpout dock to empty the holding tank and rinse it.

This picture was taken after cleaning and rinsing the holding tank.



Much of the 8 gallon concoction went right into the holding tank and cleaned it in 2 days.

Armed with this new found knowledge, I went back to my slip and made numerous 4 gallon batches that I pored into the pumpout deck port. About every 4 batches I would check the holding tank for Thermal Nuclear Reactions. I decided to keep the liquid level about an inch below the vent based on previous experience.

This is what the tank looked like before I started:



This is what it looked like 2 hours after filling the tank. Clearly the concoction is dissolving the stuff on the walls.



This is what it looked like 2 days later:



And this is what it looked like after pumping it out:





Conclusion:
Clearly the Tide and Sodium Percarbonate dissolved the residue without any agitation required. Could I use less of each, possibly. Mixing it up in batches was clearly a safer approach. Some of the residue on the walls settled to the bottom while some floated to the top of the liquid. Staying below the tank vent and flushing the vent line afterwards is important!

I liked the idea of cleaning and flushing the toilet plumbing and feel confident that neither of the chemicals will attack the rubber parts based on dilution and duration. Will be heading to the boatyard in a week or so and will probably go through one vacuum pump to check the duck bill valves.

Ted

 

[Bacchus]

Ted
Thanks for posting the + / - of your experiment - good info.
I'm curious - do you use any tank treatment on a regular basis?

I started using the unnamed treatment along with an occasional heavy dose of Oxyclean and found it did a similar job of cleaning up my tank. I do try to do an extra clean and several flushes at / near end of season before we pull for winter. I've read on RV forums that the addition of Calgon water softener helps breakdown and remove the slime / sediment that sticks to the tank & sensors and started using it at/near end of season for the final clean outs.

The above treatments seem to eliminate the hard build up and the flushes remove sediments that don't get removed with the initial pump out.

 

[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.

-Chris

 

[FF]

Is the purpose of this drill to clean the sensors?

Otherwise, why do you do it?

Stuff stuck to the tank walls probably does not reduce holding tank volume enough to measure?

 

[O C Diver]

Is the purpose of this drill to clean the sensors?

Otherwise, why do you do it?

Stuff stuck to the tank walls probably does not reduce holding tank volume enough to measure?

I have no sensors in the tank. As stated in the original post, I couldn't see the liquid level easily, to know when to pump out.

Secondly, I wanted to keep the plumbing clean. Have read a few threads where the sludge buildup in the bottom of the tank inhibited or prevented being able to pump the tank out.

Ted

 

[O C Diver]

Ted
Thanks for posting the + / - of your experiment - good info.
I'm curious - do you use any tank treatment on a regular basis?

I started using the unnamed treatment along with an occasional heavy dose of Oxyclean and found it did a similar job of cleaning up my tank. I do try to do an extra clean and several flushes at / near end of season before we pull for winter. I've read on RV forums that the addition of Calgon water softener helps breakdown and remove the slime / sediment that sticks to the tank & sensors and started using it at/near end of season for the final clean outs.

The above treatments seem to eliminate the hard build up and the flushes remove sediments that don't get removed with the initial pump out.

I don't use any other tank treatment other than to flush a bowl of freshwater through the system daily. I have a large vent line and haven't had an odor problem since replacing the white sanitation hose with the black good stuff.

Ted

 

[O C Diver]

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.

-Chris

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.

Ted

 

[JohnEasley]

Ted,

Thanks for posting the steps you took and their relative successes. Great information and terrific results.

John

 

[Russell Clifton]

OC Diver. Sure you have your colors right?

 

[Cigatoo]

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.

Ted

I think you are on to something here. After reading about Sodium Percarbonate I would guess that it is the active ingredient in other holding tank products. Rapid release of oxygen when it breaks down is key.

Thanks for experimenting and taking the time to post!

 

[Marlinmike]

Thanks for sharing and all the gory details! lol

 

[Bacchus]

I don't use any other tank treatment other than to flush a bowl of freshwater through the system daily. I have a large vent line and haven't had an odor problem since replacing the white sanitation hose with the black good stuff.

Ted

Ted
You might try adding a small dose (TBSP or two?) of the Sodium Percarbonate to the daily flush and see if it keeps the tank clean vs doing the high dose after the build-up - That's the recommendation w/ NoFlex and it seems to keep it clean once it does the initial clean-up.

 

[O C Diver]

OC Diver. Sure you have your colors right?

Not sure which colors you are referring to.

Ted

 

[O C Diver]

Ted
You might try adding a small dose (TBSP or two?) of the Sodium Percarbonate to the daily flush and see if it keeps the tank clean vs doing the high dose after the build-up - That's the recommendation w/ NoFlex and it seems to keep it clean once it does the initial clean-up.

Yes, I'm considering that. I think dwell time will be a factor. My guess is that it needs to be dissolved and sit in the plumbing for a number of hours to be effective. Also wondering how effective it will be in an exponentially greater quantity of poop.

I do annual preventive maintenance on my sanitation system and feel this process will be a great prep before doing the inspection / service.

Ted

 

[sunchaser]

OC
Like FF, I wonder if all this effort was necessary. Part of the fun of boating though is being OC and anal, we all do it in several ways

Given your boat smarts, you could easily come up with a variety of ways to sense holding tank level. As others have suggested, No Flex and other common tank additives seem to do the trick for many of us.

 

[dhays]

OC
Like FF, I wonder if all this effort was necessary. Part of the fun of boating though is being OC and anal, we all do it in several ways

+1

I wish I could just visualize the tank level as OC can.

Now that I don’t use float sensors in my tank, I don’t have the same need to keep the tank as clean. However, I still rinse the tank really well whenever I do a pump out. I also have been using NoFlex regularly which seemed to keep my old float sensors clean anyway.

Even so, I love to read about other’s experiments. I have not heard about the idea of using TSP in addition to NoFlex. It makes sense to me. For decades I always had some TSP around, left over from my window washing business back in my college years. The stuff is pretty toxic though and I’m not sure how easy it is find these days.

 

[O C Diver]

OC
Like FF, I wonder if all this effort was necessary. Part of the fun of boating though is being OC and anal, we all do it in several ways

Given your boat smarts, you could easily come up with a variety of ways to sense holding tank level. As others have suggested, No Flex and other common tank additives seem to do the trick for many of us.

I had considered the other options of tank level monitoring (have a Heart Tank Tender system for all the other tanks). Decided the simplicity and reliability of flashlight against a translucent tank was too reliable to pass by.

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 freely admit to having become obsessed with getting the tank completely clean. I will also admit to having OCD when it comes to preventive maintenance. While there are some here who prefer to fix what's broken while becoming reacquainted with their own poop, I prefer to do PM on a clean system at a time and place of my choosing.

I'm not sure, but I think FF coined the phrase, "Cruising is boat repair in exotic locations ".

Ted

 

[HeadMistress]

Very interesting thread! And I'm not too old yet to learn something new.



I'm not sure, but I think FF coined the phrase, "Cruising is boat repair in exotic locations


It's one of a pair of definitions found in a number of sailing "dictionaries:"

"Cruising: sailing your boat to exotic destinations to work on it.

Yachting: cruising your boat to exotic destinations to pay someone to work on it,"



Others include "Anchor: Any of a number of heavy hookshaped devices that are dropped over the side of a boat on on the end of a length of line and/or chain, and which are designed to hold a vessel securely in place until a) the wind exceeds 2 knots, b) the owner and crew depart, or c) 3 am.


--Peggie

 

[BradC]

Just to add my $0.02; After reading a number of success stories on an RV forum I belonged to I started using Noflex and then later transitioned to just generic sodium percarbonate at the rate of about a teaspoon every flush. I was able to use comfy store bought TP and saved a ton a $$ on both the Marine TP and the NoFlex and never had a clog with easy pumpouts. 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.

My understanding is the sodium percarbonate oxidizes and creates a good aerobic environment, destroys anaerobic bacteria (and the associated smell) and then becomes an inert environmentally friendly concoction. In the process it breaks down paper and solid wastes so the only thing left in your tank is liquid, which is easily pumped.

The key is persistent and regular use to be effective because, my guess; the oxidation process required is time limited due to the reaction process.

 

[Symphony]

thanks for the complete write-up with pictures and the very valuable parts that did NOT work. we always learn more from failed experiments.

You never know what is enough until you have too much - William Blake

 

[timb7734]

Steel tank and sodium percarbonate

Will this chemical eat the metal in steel tanks, of which mine are built into the hull?

 

[O C Diver]

Will this chemical eat the metal in steel tanks, of which mine are built into the hull?

Are they steel or stainless steel. Hard to imagine a steel tank used for sanitation that is built into the hull.

Ted

 

[HeadMistress]

Will this chemical eat the metal in steel tanks, of which mine are built into the hull?

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

 

[porman]

What Peggie said. A friend lost the use of his Hunter sailboat for the whole summer because the built in aluminum holding tank started to leak in June. The repair was just completed last week.

 

[rslifkin]

I just replaced an aluminum tank this summer. Amazingly, the thing made it 33 years and was just starting to weep at 2 of the lower corners. Came out in 1 piece and the rest of the tank externally looked fine (didn't look at the inside). Made from .090" wall 5052 aluminum according to the data plate on it. And that tank had salt water flushes feeding into it for all but the last few weeks of its life.

New tank is plastic, of course, as I have no idea how that aluminum tank lasted as long as it did and that's not a job I want to do twice.

 

[Comodave]

Maybe it was never or rarely used to last that long.

 

[rslifkin]

Maybe it was never or rarely used to last that long.

If you're referring to mine, the boat has been in the family for 32 of those 33 years, so I can confirm the tank has definitely had consistent use for its whole life, although considering a few family members' flushing habits, the contents were likely a bit more diluted than some would experience.

 

[Comodave]

Then that is pretty amazing.

 

[rslifkin]

Then that is pretty amazing.

When I found the first signs of leakage and went in to replace it, I was half expecting the thing to break apart when I went to move it. I was shocked at how intact it still was. And that the wood supports under it were still in good shape and could be re-used for the new tank.

 

[Flybull]

very interesting thread! And i'm not too old yet to learn something new.



i'm not sure, but i think ff coined the phrase, "cruising is boat repair in exotic locations


it's one of a pair of definitions found in a number of sailing "dictionaries:"

"cruising: Sailing your boat to exotic destinations to work on it.

Yachting: Cruising your boat to exotic destinations to pay someone to work on it,"



others include "anchor: Any of a number of heavy hookshaped devices that are dropped over the side of a boat on on the end of a length of line and/or chain, and which are designed to hold a vessel securely in place until... all necessary repairs are made.


--peggie

fify