Holding Tank Location

[neil1967]

I intend to fit a holding tank to the mid/aft head on our Oyster 406, as we will be moving her to the Netherlands next year and in the longer term will take her to the Med and probably spend some time in Turkey. I have read as much as I can, including old threads. I have identified 2 possible locations for the tank:

Spare space in the aft cabin - pros: near the heads (1.5m), can use existing seacock, space is currently unused (knee-room under a table); cons: would have to be a custom made, odd shaped tank (expensive), would be below the waterline so installation more complex and would need a pump/maceator

Aft locker - pros: tank would be above waterline (gravity empty), rectangular tank (cheaper), relatively simple installation; cons: linear distance from head to tank would be approx 4m, drop from siphon break to tank would only be 10-15cm, new seacock required in aft locker, which would either need to be electrically operated or some form of mechanical linkage (seacock would normally be 5-10 cm above waterline, in the bottom of the hull, rather than in the transom).

I would be grateful for views on the best location for the tank, and anything else I should take into consideration.

Thanks

Neil

 

[sailorman]

ask on the oyster mail forum. gotta go out & will look it up upon rtn

 

[RupertW]

I like simple systems and a gravity emptying tank which the outlet always goes through is the simplest way I've encountered. If you also have a deck fitting directly above the tank and in line with the outlet at the bottom straight down to the seacock then you can rod all the way from deck to sea. One seacock, no diverter or other valve needed. Not sure you need a siphon either but that may be because the tank vent performs the role.

 

[prv]

I like simple systems and a gravity emptying tank which the outlet always goes through is the simplest way I've encountered. If you also have a deck fitting directly above the tank and in line with the outlet at the bottom straight down to the seacock then you can rod all the way from deck to sea. One seacock, no diverter or other valve needed. Not sure you need a siphon either but that may be because the tank vent performs the role.

I agree with all that. No need for a siphon break - water won't jump from the surface in the tank up to the inlet in the top face, and the tank breather ensures that airspace is present. A cable-operated linkage for the seacock shouldn't be too hard to arrange either (although I wouldn't recommend installing the seacock "5 to 10cm above the waterline" - will make emptying a rather unpleasant process). However, the 4m of hose is not ideal - Jabsco specify 7 pump strokes per metre to clear the hose, so call it 30 in your case. That's a lot of pumping every time, and a lot of extra water chucked into the tank.

Pete

 

[yerffoeg]

Holding tank location

One thing to consider is the breather tube. Go for wide bore; ours is 1.5 inch standard sanitary hose. this allows the contents of the tank to decompose aerobically (no stink) rather than anaerobically (ie major stink).

 

[sailorman]

I intend to fit a holding tank to the mid/aft head on our Oyster 406, as we will be moving her to the Netherlands next year and in the longer term will take her to the Med and probably spend some time in Turkey. I have read as much as I can, including old threads. I have identified 2 possible locations for the tank:

Spare space in the aft cabin - pros: near the heads (1.5m), can use existing seacock, space is currently unused (knee-room under a table); cons: would have to be a custom made, odd shaped tank (expensive), would be below the waterline so installation more complex and would need a pump/maceator

Aft locker - pros: tank would be above waterline (gravity empty), rectangular tank (cheaper), relatively simple installation; cons: linear distance from head to tank would be approx 4m, drop from siphon break to tank would only be 10-15cm, new seacock required in aft locker, which would either need to be electrically operated or some form of mechanical linkage (seacock would normally be 5-10 cm above waterline, in the bottom of the hull, rather than in the transom).

I would be grateful for views on the best location for the tank, and anything else I should take into consideration.

Thanks

Neil

sent PM

 

[neil1967]

Sailorman - thank you, PM received.

Not having a siphon break would make installation easier - I hadn't thought of that!

Neil

 

[RichardS]

If you also have a deck fitting directly above the tank and in line with the outlet at the bottom straight down to the seacock then you can rod all the way from deck to sea.

I can vouch for that being a "lifesaver". I didn't realise that our fittings were vertically in line for a couple of years but once I discovered it, blockage clearing suddenly became so much easier!

Richard