Heads plumbing arrangement, sanity check please.

[Tranona]

Well I do use the argument for sea cocks. I know from experience of several yachts that it is a potential blockage point. One cannot, sensibly, do away with the valve at the sea cock, so one has to deal with it. One CAN avoid a "Y" junction in the outlet hose from the heads. The bore is NOT really smooth. There is the change in diameter from fitting to pipe for a start. Simply because the fitting sits inside the pipe. So your comment was, in effect, missleading. Then there is the issue of the bend. It is not a straight run. Furthermore, it only takes a slight miss-alignment of the handle to spoil the alignment of the valve itself, within the bore.

For goodness sake! It is 38mm bore - more than double the size of many bilge pump outlets and just pumping water that has come through a strum box with a 5mm screen. It is only for the odd occasion when the bilge needs emptying and in the vanishingly unlikely event of a blockage is not the end of the world.

You are just creating imaginary events which even if they did happen would not impede water!

 

[Daydream believer]

For goodness sake! It is 38mm bore - more than double the size of many bilge pump outlets and just pumping water that has come through a strum box with a 5mm screen. It is only for the odd occasion when the bilge needs emptying and in the vanishingly unlikely event of a blockage is not the end of the world.

You are just creating imaginary events which even if they did happen would not impede water!

But it is not the bilge pump I am thinking of. You are ignoring the heads pump has to pump efluent past the extra "Y" valve. Just try & look at the wider picture will you.
But of course you know better, so perhaps left to the Op to decide, do you not think.