Pumping Out A Holding Tank

[Emjaytoo]

Our new boat came with a holding tank as standard, complete with deck pump out point. Although our marina has a pump out facility it is difficult to access and so we have not yet pumped the tank out from the deck access point.

What experience do forumite have of pumping out?

When I look at the hose at the marina it looks too big to go in the pump out deck fitting (the deck fitting looks the same size as the water & diesel deck fittings), also the hose from the deck fitting down to the bottom of the holding tank has several tight bends in it.

 

[boatsRus]

Pumping out your holding tank should not be a major drama. Your marina should be able to lend you an adaptor to fit your deck outlet - if not, your local Chandler should be able to sell you one. Also worth buying a box of disposable plastic gloves - for obvious reasons. The ease of emptying your tank will depend on how well maintained the pump-out facility is - if it isn't capable of creating enough of a vacuum to suck the contents out of the tank, it isn't much use. Once I have got my holding tank as empty as possible, I normally refill it with fresh or salt water through the pump-out hole, and then pump out again. Total time - about 10 minutes. The alternative, of course, is to go well out to sea and empty through the hull valve - unavoidable sometimes, but not very pleasant.

 

[Dyflin]

AFAIK, the nozzle only has to cover the tank access/deck point onboard to form an airtight seal. The machine builds up a vacuum (it takes about 1 minute), the valve is opened and hey presto, [--word removed--] goes out.

There should also be a hose to fill the tank with water afterwards to rinse it out. Please don't be tempted to top up any other tanks with this hose... /forums/images/graemlins/grin.gif

 

[Emjaytoo]

If you rely on creating a vacuum to suck out the contents, how do you equalise the negative pressure in the holding tank? Surely it would collapse!

 

[Dyflin]

There must be a vent somewhere? Poo goes in, air goes out, poo goes out, air goes in.

 

[Emjaytoo]

[ QUOTE ]
the valve is opened and hey presto

[/ QUOTE ]

I don't think I have a valve to open. I have two seacocks for the heads - water in and holding tank out. The heads pump emptys through the holding tank, unless you shut the cock, in which case it backs up in the holding tank until such time as you empty it, either by opening up the cock (out at sea) or pumping out through the deck fitting.

 

[oldsaltoz]

have pumped out in several marinas, they had a collection of hoses of all sizes.
As mentioned above flush it after first pump out.

Avagoodweekend......

 

[Dyflin]

The valve is on the pump out nozzle. It's really very simple and nothing to get troubled about, the marina staff will know exactly what to do (at least they do in my marina!).

 

[Emjaytoo]

Just to the right of where it says "CRUISER" there is a S/S fitting not dissimilar to the one on the transom that spewed diesel out the first time I filled up with fuel, so that must be the breather? I've never noticed any smell on the starboard side of the boat tho'.

 

[pvb]

Big vent is needed...

Holding tanks need a big air vent - 38mm diameter is often quoted - in order to stop the tank collapsing under the pump-out vacuum. A big vent also helps ensure that enough air can get to the tank in normal usage (smells start occurring when there isn't enough oxygen in the tank).

 

[Andrew_Fanner]

Re: Big vent is needed...

Probably daft but; how do you know the tank is pretty much full? Can't pump into it or something else? I have no gauge.