Black water tank capacity.

[Mudisox]

I am aware that the probable answer is as large as possible but for two people, and possibly occasional guests- what is the minimal size?

50l,75l, 100l ?

 

[silver-fox]

I have read you should allow 1.5l per visit and flush. So all you need to decide is how many visits and how long before you empty the tank!.

 

[Tranona]

There are just too many variables - particularly the number of days you want to be independent. 50 or 60 litres is typical in something like a production 35' boat which might give 3-4 days for a couple. Once you get above that sort of capacity you have serious space problems in many boats so your decision really revolves around how much space you have available, or are prepared to sacrifice.

 

[vyv_cox]

My tank is much as Tranona says, 52 litres I think, two people, 35 ft boat. This gives us about three days but there is a big difference if you can divert flow from the toilet to either the tank or overboard. This allows you to put liquids straight out while putting solids into the tank. With our previous 25 litre tank that had this facility we could manage easily for four days without pumping out.

 

[duncan99210]

We have a 90 litre tank plus the ability to easily shift between tank and straight to sea. Just using it for solids we've never been constrained by capacity; we rarely stay more than a week or so in a place.

 

[jordanbasset]

We have a 90 litre tank plus the ability to easily shift between tank and straight to sea. Just using it for solids we've never been constrained by capacity; we rarely stay more than a week or so in a place.

That is the system we had, only had a 50l tank but never had a problem with it being full, seldom stayed more than 5 days or so in any one place.

 

[charles_reed]

25litre saddle-tank, lasts 2 people about 3 days - providing you don't flush too much.

 

[Mudisox]

Many thanks to all for the personal hygeine knowledge imparted.
60l tank ordered and diverting of my own age related night visits!

 

[keithgdg]

I am fitting two 85l tanks in my bilge, indeed they're in situ now, but I have a long encased keel so have the space. I went as big as I could get in there, allowing for the access hole size. Suggest you make up some cardboard templates and see what you can get. Bigger is better!!!!!