Black water holding tanks

[Peter]

I’m fitting my yacht out for long distance cruising. Part of the work is installing a black water tank. What I am finding difficulty in is what is a reasonable size for one of these items. Based on 2 people, with what would be a good size? Any ideas on materials, fittings for pumping out, location, or any other info on black water tanks etc. Thanks for any help

Peter

 

[Guest]

The size required depends on what you aim to do. No tank will last very long so if you plan to spend weeks or months in a harbour it will not be of much use (many harbours still do not have any facility for pumping out so you have to go off-shore to do that. Hopefully this will improve with time). I think mine is 40 litres, which is good for 3-4 days maximum with two kids.

For the tank, use stainless steel if possible. I had a rubber tank once, and there was always a smell around it. Use ducts of the highers possible quality for the same reason. And place the tank, if possible, in a locker which is ventilated.

To avoid clogging, use a high-effect Whale-pump or similar for emptying at sea. The deck fitting for emptying with a suction pump is standard size, similar to the fitting for diesel or fresh water (but a different colour code !).

Andreas

 

[gunnarsilins]

I have installed.....

....one in plastic of Vetus make. I had it for two seasons and I cannot detect any smell. Emptying is by a simple Plastimo (membrane type) pump.
The size is 100 litres and with two persons onboard we can stretch its capacity up to most 6 days, when both doing all business onboard and with no visits to stays or toilets ashore.
The toilets are Lavac Popular. I assume different types of toilets uses different amounts of flushing water.

 

[Sirus]

I did read that the average person produces between 6 to 12 litres of waste a day seems a bit high,maybe this was after 15 pints and a good curry.

 

[jtwebb]

I found 30 Imperial Galls took 20 man days of 'input'. This was accompanied by the comment to a reluctant crew that when it was full we had to go sailing as there was no pump out! Hence, care was taken over the amount of flush water.

J Webb

 

[tomboy352]

We have a s/s tank (15ltr) mounted in the locker immediately behind and above the w.c. With three p.o.b. we have to be careful with the quantity of flushing water used but can just squeeze 36 hours. After that it is back to sea or keep your legs crossed.

 

[Guest]

I find that our 20 gall tank lasts 2/3 days for self and wife.

Would strongly recommend piping up as much as poss of the system in solid ABS piping. You can buy it from B&Q, and Marley make bsp end fittings which will connect with hose tails from Lee sanitation allowing you to easily connect 41mm ABS pipe to flexible. Apart from saving lots money, the ABS will tolerate standing sewage without niffing. Flexible will not since the process that makes it flexible also makes it slightly porous on a microscopic scale. Ask Lee sanitaytion if you want confirmation of this.