Enzyme cleaners for tanks and blackwater pipes

Oct 26, 2026
1
Hallberg Rassy 55 Cowes
I've read a number of threads on this forum regarding using enzyme cleaners for holding tanks and pipes, but I'm cruising outside the US and haven't found any of the enzyme cleaning products referenced. I have a stainless steel holding tank, fresh water flush and no toilet paper gets flushed. In order to clean the accumulated waste in the tank and pipes that I assume must be there after 14 years of use, I'm looking at using enzyme tablets available from a janitorial supplies company in the UK (BioHygiene - Urinal & Toilet Cleaner) i.e not made specifically for boats. Is this a bad idea? Thanks for your advice!
 
Jan 11, 2014
14,267
Sabre 362 113 Fair Haven, NY
The issues with household and commercial toilet cleaners is their negative affect on the rubber and plastic parts in most sanitation systems.

I've not tried it yet, however, dishwasher detergent may be an option since is its designed to loosen dried grease and food debris from dishes. Throw some in the tank and go sailing letting the boats motion agitate the cleaning solution.
 
Jan 19, 2010
13,083
Hobie 16 & Rhodes 22 Skeeter Charleston
I like @dlochner 's idea about a strong detergent. I have also wondered about using products designed for septic systems. I'm thinking about something like RidX liquid
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I don't have ANY experience using this on a boat but I have used it a lot. I raised a family of 4 kids (6 of us in total) in a house on a septic system. I was very diligent about using this once a month. After 15 years we had the septic guy come out to pump the tank and he said it didn't really need it. Everything was still open and flowing. This is enzymes plus "good" bacteria. I can't imagine how it could hurt to try it.
 

colemj

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Jul 13, 2004
1,175
Dolphin Catamaran Dolphin 460 Mystic, CT
Enzyme tablets won't do much good for the pipes, as that buildup tends to be inorganic salts. If you have 14yrs of crud on the bottom of the tank, enzymes might not help much there either, as that tends to be compacted and hard.

Enzyme treatment works best as a regular maintenance thing, and not a problem solver.

Do you know you really have a problem with crud and salt buildup?

Mark
 
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MFD

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Jun 23, 2016
303
Hunter 41DS Pacific NW USA
Sodium percarbonate mixture will create oxygen similar to Noflex Digester and oxygenate the existing good bacteria and also naturally loosen/emulsify crud as part of its own process of breaking down.
Citric acid mixture for hard scale (like the hoses). Will also help somewhat with the bottom/sides of the tank if it is hardened up.


Both are common for the restaurant industry and should be able to found anywhere in the world. Sodium percarbonate as a cleaning agent, and citric acid as a food additive.
Both come as granules/powder, so easy to store what is leftover on the boat. The citric acid in particular can be useful for other boat maintenance things.

Do NOT do both at the same time.
Do NOT use if you have an aluminum holding tank (which you do not).

Be cautious/safe with the mixture ratios and how long you leave it in - find from different Internet sources, then guesstimate :) - and do it multiple times rather than trying to overdo each in one shot.

If there is lots of crud in the bottom of the tank - put ice cubes in along with the cleaning mixture and go sailing in some bumpy water. Highly recommend this step (at least the sailing part) even if there is not a lot of crud in the tank.
 
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colemj

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Jul 13, 2004
1,175
Dolphin Catamaran Dolphin 460 Mystic, CT
I think ice cubes would melt almost as soon as you got the sails up.