Holding tank cleaning

[captain465]

I have a boat that is now 27 years old. Have two 15 gallon poly tanks that have been well used. I am sure that there must be a layer of sludge on the bottom that just cannot be removed through pumping out methods. I am thinking that either bleach or hydrogen peroxide added to the tanks will help to break up the sludge and then repeated rinsing / pumping out with fresh water and thus clean out the sludge. Has anyone ever done this, or utilized another method?

[cfarrar]

Do your tanks have inspection ports? The sure way to remove the salt-cake deposit is open the tank, chop up the deposits with a blade-type tool, and remove it with a scoop. An occasional flush of white vinegar through the toilet should maintain the system. Avoid bleach.

[sailorboy1]

I would be cautious with adding peroxide! If you used a high enough concentration and there is a biomass the reaction could result is a pretty high spike in oxygen and you could make a bomb.

Have you tried the basic of just running a garden hose into the tank to break up and then flush out?

[HappyMdRSailor]

I would be cautious with adding peroxide! If you used a high enough concentration and there is a biomass the reaction could result is a pretty high spike in oxygen and you could make a bomb.

Could you imagine the headlines ????

"BOAT OWNER KILLED BY S#%$T BOMB"

Definitely not the most dignified way to move on....