blockage in holding tank - how to clear it ? chemical or prodder

[PaulR]

heads wouldn't pump clear this weekend - instead once bowl dry and left some gradual liguid flow back into bowl over period of hours and a nasty niff!

pump seems fine so suspect blockage in holding tank outlet - no pump out facility from deck just the main out pipe from head into stainless tank which has vent and outlet leading to through hull seacock - managed to remove out hose from seacock and seacock clear but blockage in hose upstream- have attempted clearing using dinghy foot pump and limited success- some liguid and waste come throught (ugh) but not convinced all is clear - 2 key questions please for the experts,

1. Is there any chemical I can pump through the heads into the tank that will dissolve/liquify blockages so that I don't have to adopt a more invasive approach?
2 If answer to 1 is no or is unsuccesfull - is there any bit of kit or technigue that others have found works interms of passing something up pipe (on or off seacock but more likely off as boatis afloat) to dislodge blockage?

boat is from 92 - and this is the second time in 5 years it has blocked - previous time after some prodding with hose disconnected it all cleared in a dramatic rush!!

guidance gratefully received and very happy to have been in long shower since getting home!!

 

[Sans Bateau]

Phew, time to sell the boat!

 

[Anonymous]

Don't know the name but I have a long stainless plumbers clearing thing about 5m long made of coiled steel.

As for chemicals, you have a problem with a stainless tank. Indeed, stainless tend to corrode through from the inside from the soil anyway often after only a few years. Maybe it is time to replace the tank for a plastic one with all new fittings or you might have a problem mid-cruise and that would be very unforgettable /forums/images/graemlins/frown.gif

 

[TonyS]

I cleared mine once by putting a hose up the outlet (the outlet wasn't far under the boat - arms length lying in the dinghy alongside). High pressure mains water cleared it in no time. The other time I put the hose in the air vent which also worked, and is easier, but runs the risk of blowing off a connection with a horrible mess to clear up! Both assume you are in a marina with mains water.

 

[theforeman]

2 things occur - should you be cleaning out a holding tank in a marina and should you be sticking a drinking water hosepipe up your loo discharge ? /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif

 

[jimbaerselman]

Two probable causes. Long term calcareous deposits breaking up and blocking crucial bends, or a special present from a visitor who wasn't aquainted properly with heads etiquette.

The former is more likely (specially after such a long time!) Unfortunately, with a stainless holding tank, you really should not use hydrochloric acid, probably the easiest cure for calcium salt blockages, since it seems to attack the protective oxide skin. Other acids are pretty weak for the job unless they're part of your annual routine.

Do a bit of diagnosis first, to determine where the block is. If it's en route to the tank, the pressure build will not be relieved by vents. If it's post tank, the vents will blow pressure off.

Almost always the best course is to do the grotty job of disconnecting the pipe, pulling it out, bashing the deposits out by banging the whole thing against the quay side, and re-installing. There's been a thread about this on 'live aboard' forum. I left a nice picture on there showing what happens to heads pipes in warm climates . . .

 

[Birdseye]

First check the simple and inexpensive. first thing to look at is the flap valve in the toilet itself. If you have 2 toilets into the same holding tank and only one is leaking back then it must be the bog not the tank that is the problem.

Flap valves get leeaky when some crud builds on the seat etc.

If it really is the tank then I would be inclined to put a healthy does of some bio digester type product in there to munch up the poo. pump out through the greather usinf a diaghpram type pump, flush with fresh water and again pump out, then try some drain unblocker. Its usually caustic soda but there are some domestic sink unblockers that are a bit less nasty. see your local Tesco.

One tip from a flotilla holiday and used long term on my old boat. Dont put anything that hasnt gone through you down the bog. Instead have a waste bin to take the toilet paper etc. It doesnt smell, is hygenic and you will never ever have a holding tank blockage. OK for the squeamish brits it takes a lilttle bit of getting used to but in other countries its commonplace

 

[nedmin]

I dont know why other boat makers dont follow the design of my Pedro. the holding tank has a large outlet pipe at about 45deg. to the hull, so that when you go above 4knts the venturi action lowers the level in the tank,as soon as you stop it refills with fresh water there is a sea cock for marina use, but as ducks dont have holding tanks I dont bother.I always use good quality toilet paper,the type that disintegrates in water. An old salt told me to always pump at least 15 times to keep pipes clean.

 

[Habebty]

explosives

 

[Bilgediver]

HAve you checked the air vent. Not just the hose but also the end fittings.

Is the tank full????? This should be possible to check by tapping it as it will sound different above and below crud line.

You need some of the Headmistresses formulas however the nearest thing available in the UK is to be found in the B and Q larger warehouse stores and sold for septic tanks. These chemicals will break down the contents.

John

 

[jimbaerselman]

[ QUOTE ]
first thing to look at is the flap valve in the toilet itself.

[/ QUOTE ] You're quite right. If there's trickle back into the toilet, the joker valve, duckbill valve or flap valve (depending on loo type) at the bowl outlet is not closing properly, and need to be cleaned or replaced. As such, this trickle back is not an indication of blockage.

I had assumed that since the OP talked about 'blockage', he'd actually met a pressure build up while pumping as well. That implies a blockage en route to the holding tank, or a blocked vent from the holding tank (whether it's full or not!) with the seaside outlet closed. A blockage downstream from the tank would only be detectable when the tank outlet is open AND the vent is blocked.

I could tell you a lovely story about our polyester holding tank who's vent blocked while it was in 'retain' mode . . . the user said 'this pump is stiff!' . . . shortly after there was this big bang . . .