Capacity of black water tank?

[coopec43]

I wonder what the average capacity of a black-water tanks are?

I've looked at previous threads on the capacity and they mention 50/60 gallons . I've checked Hallberg Rassy and Beneteau manuals but they don't give the capacity of their black water tank

Mine is only about 35L (10gal) but if I was in a marina I'd use the marina toilets when possible.

[JimsCAL]

10 gallons is pretty small. I think something around 25 or 30 gallons is a minimum size. Bigger is (usually) better.

[BlueH2Obound]

Our forward black water tank is 204 US gallons. Aft black water tank is much smaller, at only 140 US gallons. We are probably the outliers for tank size though . . .

[Mike OReilly]

Depends on where, and how, one uses their boat.

One of the reasons I switched to a composting head was due to limited black water capacity. I was tired of organizing my cruising around how long I could last before getting a pump out. The composter essentially gives me unlimited range/time.

For the record, my previous boat, which was designed for Great Lakes travel, had a 50 gallon holding tank. My current boat came with a 35 gallon tank. Both were too small for my needs/wants.

[coopec43]

Originally Posted by JimsCAL

10 gallons is pretty small. I think something around 25 or 30 gallons is a minimum size. Bigger is (usually) better.

Thanks for your advice.

I most certainly won't argue with that but I was constrained with the room I had. I didn't want to go for a complicated design as I'm sure that would have led to noisome smells.

I did have plans to install a "compost toilet" in the aft cabin (and that is still a possibility)

Maybe I should go back to see what Peggy has to say but I don't think she likes "compost toilets"

[aqfishing]

Our Leopard 40 has 29 USgal in 2 tanks.

[coopec43]

Originally Posted by BlueH2Obound

Our forward black water tank is 204 US gallons. Aft black water tank is much smaller, at only 140 US gallons. We are probably the outliers for tank size though . . .

Yes, I just looked at the size of your yacht - 50ft


I think my plan to install a compost toilet in the aft cabin is sound. (The one I was looking at sent the urine straight over the side)

[coopec43]

Originally Posted by aqfishing

Our Leopard 40 has 29 USgal in 2 tanks.

Two tanks? Yes that is a distinct possibility. (I was planning to put X3 freshwater tanks in but only put two in so I could use that space. (I plan to install a water-maker)i

[Mike OReilly]

Originally Posted by coopec43

I think my plan to install a compost toilet in the aft cabin is sound. (The one I was looking at sent the urine straight over the side)

A composter solves all your problems (but creates new ones ).

One note though, at least in North American, having the urine plumbed as direct discharge would mean you could not venture into any No Discharge Zone area, nor travel within 3 nm of land. I don't know the laws in Australia.

[leecea]

We'd struggle to live with 10 gals. Ours is 30 gals.

I see the advantages of a composting head but don't understand how we could use one. It must be very dependent on what access you have for disposal. I can't think of a place we've been where we'd be comfortable doing that.

[CSYChip]

I have 2 tanks, one for each head, one is 35 gallons, the other 30. That is good for 2 weeks between pump outs with 2 people on the boat.

[rslifkin]

Our tank is 70 gallons for 2 heads. With 2 of us on board and never using facilities ashore it's comfortably good for 10+ days. If we had more people with us regularly then I might want a bit larger tank.

35 gallons should be a manageable size, but depending on your cruising grounds, bigger can be a convenience. In our case we're typically a few days away from anywhere we can dump the tank overboard. And our tank is big enough that we don't generally have to go searching for a pump out, we'll almost always have an opportunity before the tank is full.

[Mike OReilly]

Originally Posted by leecea

I see the advantages of a composting head but don't understand how we could use one. It must be very dependent on what access you have for disposal. I can't think of a place we've been where we'd be comfortable doing that.

I mostly dispose at sea, or on land in remote places. Occasionally I have used marina garbage bins. This is rare for my cruising grounds, but it's no big deal disposing this way -- just like taking out the trash.

[Dockhead]

120 liters here. Way too small for Great Lakes cruising. Used carefully it will last a few days with 4 or 5 people on board. Which is more or less good enough in areas where you can dump the tank 9 miles off, and/or where there are many pumpouts.

I think for normal cruising areas (not the Great Lakes), the black water tank should be sized to last about as long as the water tankage. For us, that's a week if water is used not that carefully.

Another alternative is LectraSan. We had that on the last boat, and it was brilliant. Can't be used in no-discharge zones though.

[SailingHarmonie]

Originally Posted by coopec43

Yes, I just looked at the size of your yacht - 50ft


I think my plan to install a compost toilet in the aft cabin is sound. (The one I was looking at sent the urine straight over the side)

Do you know that discharge of urine overboard from a marine sanitation device is illegal in the USA coastal waters?

From the EPA Website:

The contents of both the liquid waste container and the compost chamber must be properly disposed of such that no overboard discharge occurs.

See 33 CFR 159.12(a) and 33 CFR 159.53(c) for the relevant statutory language.

We can argue all day if that is a "good" rule or not, but it is the case and the USCG will enforce it.