Blackwater Options

[TiggerToo]

I am beginning to consider installing a blackwater tank system on Tigger.

I would appreciate general comments/advice.

But also, more specifically, I have been quoted for two options: a 25lt tank and a 60Lt tank. What would peeps say to that? Has anyone here got tanks of this sort of range? If yes, what do you consider adequate? Our use, realistically, would be for short-handed crews (2-3 up). Is 25lt likely to be sufficient? Conversely, would 60Lt be OTT?

 

[tillergirl]

I had a 56 litre (bespoke) tank. Was fine for 4 people for say 3/4 days. 25lt I would suggest is a little small.

 

[pvb]

Go big!

 

[Tranona]

Typical liquid only flush is a minimum of 2l, solids more, so 25l gives less than 10 uses! Modern boats of your size have tanks of between 60-80l but of course they are designed to have tanks. So 60 is a reasonable size if you can fit it preferably as a gravity rather than a pumped system. Gravity is much the better way to go and i would sacrifice a bit of capacity - in my old Bav 37 we managed to fit 45l custom made with a gravity system.

 

[Neeves]

I don't know your rules nor where you sail

But

If you are out in the open sea do you really use a blackwater tank, or simply flush overboard. You only need a 'large' tank if you are sitting in a marina with 2 or 3 people pinned down below and unable to use the facilities provided by the marina. In this case you then need to flush the tank (outside the marina - in the open sea) and not leave the part filled black water tank until you next go to sea, next weekend, next month - so it needs flushed after use.

Its not so much the tank size, I would think, unless you are living on board but the convenience of shore side facilities and how you use the yacht.

Guessing on yacht usage - I'd go for the small tank and set strict rules on usage. Id also consider how you are going to empty and flush the tank.

Jonathan

 

[Boathook]

I would go for the 60 litre. I fitted a 40 litre size and it soon fills up! If possible fit a diverter valve so that only no. 2's go into the tank. Both Leesan and tek tanks have good information on their web sites.

 

[harvey38]

Just had a 200l fitted to a 38 ft MOBO, better to have and not need than need and not have!

 

[BabaYaga]

My choice would definitely be the 60 l tank. If that means a pumped, under water line system, don't be deterred. These can work fine, mine has for 40 years.

 

[Simon 420]

Go big with a diverter valve. We have a 90l tank on our boat which will give us about 7-10 days worth of solid waste capacity, slightly less when we're on the river and discharging fluid waste as well as solid into the tank

Also remember that the air filter elements will need to be changed every year- but do that with an empty tank and the windows open!

 

[johnalison]

Our boat came with a 60l tank which is stainless steel. This is fine for four people for a couple of days but I wouldn’t want anything smaller. The instructions told us not to retain the contents for more than two days. I presume that this is because of the corrosive effect of urine and that a plastic tank wouldn’t have this concern. We have generally stuck to this but a generous helping of seawater probably helps too.

 

[Lee Shaw]

It also depends on whether you have a manual or electric flush. Two of us quickly filled a 45 litre tank on a charter AWB in Greece. The flush was electric and pumped a large volume each time.

 

[TiggerToo]

Thanks guys! This is all extremely valuable information.
I am talking to several installers/yards to see what they come up with, but your (joint) experience is great.