Desludging the blackwater tank

[rwaldrop13]

Good afternoon -

Anyone had to deal with de-sludging or removing buildup from their blackwater/holding tank? I was pretty aggressive with this for the first 3-4 months we owned our boat, and gradually moved to a regular routine pumping twice a week while our adult children lived aboard with us. They moved out about 3 weeks ago, and Friday morning I noticed that the heads were acting like the tank was full even though I pumped out on Wednesday. I found the vent filter was clogged and replaced it, along with backwashing the vent hose into the tank while pumpout running, only to have same issue recur today.

I was wondering if anyone had tried Rid-X or a similar product to reduce or liquify sludge in the tank, since I believe it is still a buildup issue. My plan for this week is to backwash thru the vent line while running pumpout tomorrow, Wednesday and Friday, repeating for at least 2 weeks.

 

[guy with a boat]

This topic has seen a lot of discussion in the past. Do a search for past threads and you’ll be busy reading for days. People have tried a lot of methods and some are very effective.

 

[Bacchus]

2 schools of thought -
- vent filter stops odors from escaping ( but can be problematic if it gets wet / clogged etc) prevents adequate air into tank, guarantees anaerobic breakdown and smelly tank
- No filter, provide adequate air to support aerobic breakdown and eliminate holding tank smell

Get and read Peggie's ( TF Head Mistress) book and follow her recomnendations.
I / and many have had very good luck with Sodium Percarbonate / NoFkex at preventing odors and breaking down solids. I'm sold on providing adequate air. See "Bacchus" website " Projects" for our holding tank bubbler system. I continue to use SPC / NoFlex and have finally found a way to add an adequate vent (most factory OEM are inadequate.

 

[Comodave]

I would get rid of the vent filter. It blocks air flow into and out of the tank. Aerobic bacteria are your friends. Anerobic bacteria isn’t your friends. I added 2 1.5” vents to the tank in our current boat. It has the factory vent filter waaay up out of possible human reach so it looks like the original factory filter, currently 24 years old. I left it in place simply because I can’t get to it. Read Peggie Halls posts about holding tanks, she it the guru. Het user name is The Head Mistress.

Some people have been using Zaal products to clean a caked up holding tank. Don’t remember the product name right now. Do a search.

 

[HeadMistress]

If the toilets are acting like the tank is full, but the tank isn't overflowing out the vent, that's a strong indication that the tank vent is blocked, pressurizing the tank and creating back pressure that's preventing the toilets from flushing anything into it. If you're lucky only the filter was clogged...replacing it should have solved that problem. If it didn't, the first thing you need to do is clear the vent. Don't try to pump out until the vent is clear...'cuz without a source of air to replace contents as they're pulled out, the pump will pull a vacuum that won't let it pull out more than a gallon or two.

The two most common locations for a vent blockage are the vent thru-hull and the other end of the vent line--that end of the hose and the vent fitting on the tank. Start by cleaning out the thru-hull...use a screwdriver blade, ice pick--whatever works. If that doesn't result in a spew out the vent, you'll need to relieve the pressure before removing the vent line from the tank to clean them out...so open the deck pumpout fitting VERY CAREFULLY with a hose at the ready. Be sure you're UPwind of it! Scrape out that end of the vent line and the vent fitting on the tank...reconnect the vent line. Now you should be able to pump out the tank.

After you've done all that, if the sludge is still soft mud, there's a way to flush it out using only water: Add 4-6 inches of water to the tank via the deck pumpout fitting--'cuz that sends the water into the tank at the bottom to stir up the sludge so it can be pumped out...do so. Repeat, repeat, repeat until you're pumping out clean water.

If you can take the boat offshore far enough to legally dump the tank, you can do this using a washdown pump and your macerator pump. Use the washdown pump to add water to the tank, then turn on the macerator pump and let it run while you continue to add water to the tank. When the discharge from the macerator pump is no longer brown, the tank is clean.

I appreciate the recommendations to buy my book (see link in my signature below). It's title (my publisher's idea) is a bit misleading...'cuz although it does deal with every source of odor on a boat and how to cure, or better yet PREVENT 'em, it's actually a comprehensive "marine toilets and sanitation systems 101" manual that explains the laws, describes all the types of systems and how they work, and will help you learn how to operate and maintain your system to prevent 99% of problems instead of having to cure 'em. 'Cuz you get to do any preventive maintenance on your terms when it's convenient...the need to cure a problem never happens when it is! And I'm always glad to answer any questions it doesn't and also many that it does.

--Peggie

 

[O C Diver]

https://www.trawlerforum.com/forums/s31/holding-tank-cleaning-easy-way-46357.html

Ted

 

[backinblue]

Thanks to Peggie, I have been using no-flex digestor for a couple years on a new holding tank and I think everything is fine. The question I have never seen completely answered, is can I just use generic sodium percarbonate instead of the no-flex? The no-flex is very expensive, so I tend to use it rather sparingly. If the sodium percarboante works nearly as good and is muc less expensive, I'd happily use more. So I guess the bottom line question is, is it better to use small amounts of No-Flex, or larger and more frequent amounts of S.P.?

 

[Bacchus]

Thanks to Peggie, I have been using no-flex digestor for a couple years on a new holding tank and I think everything is fine. The question I have never seen completely answered, is can I just use generic sodium percarbonate instead of the no-flex? The no-flex is very expensive, so I tend to use it rather sparingly. If the sodium percarboante works nearly as good and is muc less expensive, I'd happily use more. So I guess the bottom line question is, is it better to use small amounts of No-Flex, or larger and more frequent amounts of S.P.?

Just one opinion and I havent run and documented experiments as Ted has but I have been very satisfied w using NoFlex but do plan on switching to generic SPC when I've exhausted my supply. I do think regular use is a key to keeping the system clean and odor free.
I have not compared tank before & after starting but I do notice the clear section of pumpout discharge hose shows much cleaner effluent than before I started using the NF. I do add some Calgon and detergent near the end of the season to do an extra cleaning accompanied by several rinses. I have noticed that it doesn't take many rinses to get clean clear water discharge

 

[porman]

Our boat has two holding tanks. I went with the SCAD system for measuring how full they are, removed the old floating level senders, and put caps on the old openings. I recently stuck a spray nozzle on a garden hose in the openings and sprayed all around the inside of the tank with a portable pump-out running at the same time. That removed a lot of the crud inside the tanks. Now I can use a flashlight on the sides of the tanks and actually see how full they are, and I think I got a couple more gallons of usable space. I got tired of waiting for the NoFlex to work and this gave me more instant gratification, but a bit smelly.

 

[rslifkin]

I've been using generic sodium percarbonate this year and it seems to work pretty much the same as Noflex. There may be some difference but not enough to be worth caring about in my experience.

 

[rwaldrop13]

I've been using generic dishwasher powder with good results but it wasn't aggressive on the residual sludge. A friend recommended this, said it got his tank scrubbed out and also someone on Hatteras forum.
Septic Tank Treatment - 1 Year Supply of Dissolvable Easy Flush Live Bacteria Packets (12 Count) - Best Way to Prevent Expensive Sewage Backups - Made in USA https://a.co/d/6swfVsa

 

[sailormike]

In the RV world I encounter sludged up mounded up tanks all the time. The nature of the beast is on an rv toilet it is easy to not add enough water and people will leave valves pulled. I found a sewer jetter that goes on a pressure washer. I hook it to a little electric portable pressure washer and it works great. you can take a hose or fitting loose and run it in and jet while pumping out and it will clean you right up. I posted the link below for a kit.

https://www.amazon.com/Hourleey-Pre...pY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU&th=1

 

[Comodave]

In our RV I put one of these in the holding tank. I would drain the tank then hook a garden hose to this flusher. It would spin around and spray the tank. Then drain the tank again. You mount it into the tank permanently. I got it at Camping World.

Tornado Permanent Tank Rinser with Remote Connection

 

[Hippocampus]

I’m big Peggie believer. From her thinking try to add nothing to tanks or heads. Aerobic bacteria are your friend. Many chemicals and cleaning agents kill them. Agree with mechanical cleaning of vents and hoses or replacement. Believe in supplying air even if this means a bubbler. On a prior boat with two tanks and two elegances had troubles with sludge. Being in the Caribbean the through hulls were left open. Sludge would build up from splatter around the entrance. Then break off and clog the exit hose or through hull. To fix it fill the tank a bit and use a plumbers helper from the outside. The compression and suction would clear it with a gush . (Shower after and swim trunks in the laundry).
Think to both treat and prevent sludge having a good aerobic environment is key. Think occasionally going out past the 3 mile limit on a bumpy day with half full tanks then opening the through hull(s) is very helpful. If not possible on a weekday when the pump out isn’t busy doing a pump out then fresh water fill. Then second pump out is helpful as well.
No chemicals. No bacteria killing detergents or cleaning agents.
Think sludge is a particular problem when boats sit with partially filled tanks. Good to hit the pump out before the slip if your boat is used occasionally even when you have residual capacity in the tanks.

 

[backinblue]

Just one opinion and I havent run and documented experiments as Ted has but I have been very satisfied w using NoFlex but do plan on switching to generic SPC when I've exhausted my supply. I do think regular use is a key to keeping the system clean and odor free.
I have not compared tank before & after starting but I do notice the clear section of pumpout discharge hose shows much cleaner effluent than before I started using the NF. I do add some Calgon and detergent near the end of the season to do an extra cleaning accompanied by several rinses. I have noticed that it doesn't take many rinses to get clean clear water discharge

Since my tank needed replacing when I bought it, I want to keep the new one as clean as possible. I've been using NF and it looks like mostly clear water during pumpout. However, I am going to try some generic SPC because I will likely use more of it since it's a lot cheaper.

 

[Comodave]

I’m big Peggie believer. From her thinking try to add nothing to tanks or heads. Aerobic bacteria are your friend. Many chemicals and cleaning agents kill them. Agree with mechanical cleaning of vents and hoses or replacement. Believe in supplying air even if this means a bubbler. On a prior boat with two tanks and two elegances had troubles with sludge. Being in the Caribbean the through hulls were left open. Sludge would build up from splatter around the entrance. Then break off and clog the exit hose or through hull. To fix it fill the tank a bit and use a plumbers helper from the outside. The compression and suction would clear it with a gush . (Shower after and swim trunks in the laundry).
Think to both treat and prevent sludge having a good aerobic environment is key. Think occasionally going out past the 3 mile limit on a bumpy day with half full tanks then opening the through hull(s) is very helpful. If not possible on a weekday when the pump out isn’t busy doing a pump out then fresh water fill. Then second pump out is helpful as well.
No chemicals. No bacteria killing detergents or cleaning agents.
Think sludge is a particular problem when boats sit with partially filled tanks. Good to hit the pump out before the slip if your boat is used occasionally even when you have residual capacity in the tanks.

Yes, she is awesome. I put a Grock Sweetank in a previous boat on her recommendation. I never put any chemicals in the tank for the next 8 years that I owned the boat. And no more stink either.

 

[Shrew]

I found the vent filter was clogged and replaced it, along with backwashing the vent hose into the tank while pumpout running

You can't backflush the vent line with a vent filter in place. This will fill the vent filter with water and block the vent. Did you back flush the vent line BEFORE you replace the inline vent filter??

Also you are reporting unrelated issues. The head fills the tank from the top. The pump and macerator discharges pull from the bottom. Both will require an open vent line to work properly.

 

[Comodave]

I would get rid of the filter. Agree that you can’t backflush the vent if you have a filter. Filters block airflow and that is a bad thing. Also a clogged vent or filter can cause the holding tank to collapse when pumping it out due to no air getting in to replace the poop being sucked out. A collapsed holding tank can be your worst nightmare.

 

[Cigatoo]

Defender has the Noflex for $19.00. Close to what I remember paying for SP. The Noflex worked better for me. Just use a tablespoon or so per person per day.

 

[rslifkin]

I think the cheapest I've found Noflex recently is about $16 / lb. Earlier this year I picked up a 9lb container of sodium percarbonate for $40. Even if I use 2 - 3 times as much as I do with Noflex it's still cheaper.

 

[backinblue]

NoFlex is about $35 on Amazon for a 1 lb container where SPC is about half that much for a 2 lb container, so NoFlex is roughly 4x the price. At the lower price, I'll be more likely to add a scoop more often, especially with a solid flush.

 

[ranger58sb]

The pump and macerator discharges pull from the bottom.

Maybe. Some installations use a dip tube for that...

NoFlex is about $35 on Amazon for a 1 lb container where SPC is about half that much for a 2 lb container, so NoFlex is roughly 4x the price. At the lower price, I'll be more likely to add a scoop more often, especially with a solid flush.

Good grief!

Fisheries Supply has NoFlex for $18.19/bottle if you buy 6 at a time. I think marinesan has similar prices...

FWIW, our tank doesn't need a "scoop" -- more like a tablespoon every day we're aboard.

Not an argument in favor of NoFlex over sodium percarbonate... just some NoFlex cost and dosage observations

-Chris

 

[Dwk]

SPC convert from NOFLEX

We have been using Sodium Percarbonate since O C Divers thread in 2019. The holding tank gets a dose (TBS) every day when cruising,so far no odors, blockage or sludge build up. I flush with MANY gallons of water after each pumpout,so far so good.

 

[backinblue]

Maybe. Some installations use a dip tube for that...





Good grief!

Fisheries Supply has NoFlex for $18.19/bottle if you buy 6 at a time. I think marinesan has similar prices...

FWIW, our tank doesn't need a "scoop" -- more like a tablespoon every day we're aboard.

Not an argument in favor of NoFlex over sodium percarbonate... just some NoFlex cost and dosage observations

-Chris

The "scoop" that comes with No Flex is probably a tablespoon, so that's what I was referring to. $18 is not too bad, but still about twice the price of SPC and not needing to buy 6 at a time. I didn't shop extensively, but $35 for a 1 lb container is what I paid and seems excessive. Hoping Peggy will weigh in again, because I'm still not 100% sure that they are equally effective.

 

[CaptTom]

Defender has the Noflex for $19.00.

It's $19.99, so really $20.

And Defender won't show you the shipping cost until you enter all your contact AND credit card information.

Nope. I'll buy from someone who gives me an honest price up front.

(Disclaimer: I used to buy from Defender all the time, and sing their praises to anyone who would listen. How times have changed!)

 

[CaoAlcan]

I sought rid of the entire black water tank and put in a Separett toilet. The “Tiny” is about the same size as a simple marine head. We empty the liquid tank every five days and the solid waste every 10 days. One couple using it, solid waste is closed up in a compostable bag. It has a small computer size fan that vents outside and runs off a 12 volt system. There is never any odour. I paid around $1,000 Canadian for mine. But, I don’t have to find and pay for pumpouts.
Wow, never thought my first post would be about this topic. Lol

 

[RickyD]

I think the cheapest I've found Noflex recently is about $16 / lb. Earlier this year I picked up a 9lb container of sodium percarbonate for $40. Even if I use 2 - 3 times as much as I do with Noflex it's still cheaper.

I'm getting Sodium percarbonate for about $3.30 a pound. I usually buy 20lbs at a time and it lasts seemingly forever. I also leave some at home for the laundry.

 

[ranger58sb]

The "scoop" that comes with No Flex is probably a tablespoon, so that's what I was referring to.

Haven't ever seen a scoop with NoFlex.

If that's what comes from the Amazon seller, maybe the scoop is why their product is so expensive.

It's $19.99, so really $20.

And Defender won't show you the shipping cost until you enter all your contact AND credit card information.

Nope. I'll buy from someone who gives me an honest price up front.

FWIW, the Fisherman's price I posted above includes free shipping... if you buy 6 or more bottles at a time.

-Chris

 

[backinblue]

I don't think the scoop is specific to Amazon. Lots of sites show it, here is a pic from Walmart. (also about $35). The high price is puzzeling. I found some SPC on Amazon, but are there other good sources?

 

[Comodave]

I have always received a scoop with Noflex.