So thanks to watching the Mother Ship Adrift YouTube channel I learnt that legislation in Turkey means that we would not be able to visit with our current seacock plans,
Basically, they have banned discharging both grey and black waste and enforce it through inspections and documentation. See this RYA page for a summary of what countries currently allow, However, we want to follow best practice and we don’t want to do the minimum we can get away with now only to need to change it in a few years.
We know (and are very happy) that discharges of black tanks (toilet waste) are being banned or severely restricted in many places. We hadn’t realised that the same was becoming true for grey water (although again we fully support putting less pollution in the sea).
So we need to make another set of changes to our seacock plans. Fortunately, this will bring us to a more “normal” system. In particular they will keep the number of seacocks down without having to do anything unusual (like our idea to connect basins/sinks to the cockpit drains).
So now we have to work out how many grey water tanks, where we put them and how big they are.
One big tank makes it easier to monitor and get inspected, installing a deck pump out for emptying is easy. However, getting both basins and the galley sink to drain by gravity might be challenging with potential for grey water to surge back into basins when heeling and pitching. With all the hoses routing along the boat a problem at any point could empty grey water all over the cabin.
On the other hand separate tanks are simpler to connect to the basins, much easier to ensure gravity drainage into the them. But they will need emptying separately and there isn’t a lot of space in the heads or galley for them. So easy install but not very convenient when living aboard. It would be a pity to have to go to harbours with emptying facilities every few days.
So I’m wondering about a hybrid system. A smallish tank under each sink/basin. That will mean anyone can simply empty a basin/sink by taking the plug out. Then a larger tank somewhere else that the smaller tanks can be pumped into. That larger tank is the only one that needs to be pumped off the boat. The pumps could be either electric or manual. I’m drawn to a non-automatic system which might seem less convenient but with valves at each end the chances of a hose failure causing lots of water to end up around the boat is minimised. It also allows us to make progress a bit at a time. So we can start with a waste jerry can under each basin/sink and move towards sophistication later.
The shower is a slightly special case. The water drains into the bottom of the boat so it will always need pumping out to somewhere. Probably not something that we will get around to this winter.