H34 Holding tank needs cleaning

[Jim Oursler in Rockwall]

I have come to the conclusion that the capacity of my holding tank must be reduced due to years of buildup of stuff. It is the factory original plastic on a Hunter 34. I think that the boat sat unused for 3 yrs by prior owner. Repeated Vacuum pumpouts, refilling and pumping out clean water rinse as well, and still have very low capacity.Short of replacement, What chemical or procedure is recommended to remove the sludge? I have eliminated all source of water entry except the new head, completely closing off the thru hull, and removing pump and vented loop, as this boat is on an inland lake. Replace remaining hoses.. and at least have a good absence of odor.After just a few flushes, I find flushing causes water to come out the thru hull vent just below the rail.. and know it's again time to go to the pumpout station.HELPJim in Dallas

 

[Mark Whitson]

Not an answer, but

You might consider putting an inspection/access hole (6-9" white plastic round hatches that screw in and out) in the top of your holding tank. That way you can see into your tank to verify if you have any problems. My Hunter 30 came with one already in it. Sure makes it nice not to have to remove the 50 some odd screws to lift of the top on the holding tank. My tank is fiberglass, part of the hull in the forepeak. Twice yearly (begining and end of sailing season) I open my inspection port to verify the holding tank is "clean".Good Luck

 

[Peggie Hall/Head Mistress]

First, you need access to the inside of the tank

'Cuz you're only guessing this is the problem. It could be several things...including a fitting boo-boo the previous owners have lived with since the tank was installed. It's even more likely that the pumpout or vent hose has developed a kink that stays open long enough to pump a little out, then collapses, causing the pumpout to pull a vacuum. So before you start dumping nasty chemicals (muriatic acid is the only thing I know of that will dissolve sludge that's turned to 'concrete') down the head, you need to take a look inside the tank to see if it IS full of sludge...and if it's not, inspect the whole system to find the problem.

 

[Jim Oursler in Rockwall]

If plastic holding tank full .. what is the cure?

I have replaced the vent hose. After about 6 trips to the pumpout station over a 10 week period, I think their machine works fine. SO now.. tomorrow I will disconnect the tank inlet and poke around with a stick. If sludge.. is muriatic acid the cure???

 

[Peggie Hall/Head Mistress]

If the sludge is still sludge...

You should be able to add water and stir it up into a pumpable "soup." But if it's hardened into "concrete" I don't know of anything that will dissolve it except muriatic acid...be careful with that stuff!! Follow directions for mixing carefully...and NEVER put it full strength into a metal tank.You might want to read the article in this forum entitled "odor control in holding tanks"...it explains how holding tank chemicals cause sludge and how to maintain the tank so it never happens.