Slow drain?

[Bigjim]

Originally Posted by ilCigno

The problem with small hoses is often air, not foul. At rest, the hose is full of air above the waterline. When draining your sink, the water tries to push the air column down, which fails of course. The air cannot escape upwards towards the sink because the diameter of the hose is fully filled with water. It's an air lock. Only bubbles of air can escape at a time and thus be replaced by water from the sink. Only when the whole hose is completely filled with water (after a long wait) a modest stream can pass thru. But by then your sink is probably already quite empty. Been there...

Apart from keeping it as clean as possible, only larger diameter (say 1" / 25mm inside) hose and fittings offers a real solution.

Absolutely correct. I'm revising the design right now. Have to find all the fittings. The Ts are kind of necessary due to two sinks and a bilge pump connection. I'm going to up the sizes to at least 1" and see if I can eliminate some of the connections.

It all worked when I was just pouring water down the drain. Once food particles got into the mix, it started to slow down. Thanks!

[Bigjim]

Originally Posted by Bobby Lex

Bigger hoses won't fix anything if they bottleneck at a seacock that's the same size as the hoses in your photo.

Bob

The seacock has at least a 1" hole. But I had to get a fitting that fit the 1/2" hose. So, if I swap out the hose barb with a larger one, I can use 1" hoses.

[Bigjim]

Originally Posted by NYSail

How far below the water line is the fitting and how close is the sink bottom to water line?

The seacock is about 12-15" below the waterline. The sink is about the same above the waterline.

[Gudgeon]

If you can use Y fittings going with the flow, T fitting disturb the flow and can cause lower flow.

[AKA-None]

This may help explain the issue

https://neutrium.net/fluid-flow/pres...length-method/

[ilCigno]

Originally Posted by Bigjim

The seacock is about 12-15" below the waterline. The sink is about the same above the waterline.

The depth of the seacock has no influence on the water flow. The column of water inside the tube is always nicely balanced to the depth of the outside water.

[Cheechako]

Are you sure your sink is 12-15" above the water line? Is it a raised galley?
Most boats are not. Seems like the problem is your sink level isn't much above sea level. Things drain super slow when that's the case.

I was on a custom aluminum boat once that would sit at the dock with 1/2-1" of water in the cockpit for a long time after a good rain. The owner couldn't come aboard and go into the cabin as he would track water all over. The boat was built with a cockpit floor too low. The cockpit was only 1-2" above waterline as best we could tell. The cockpit had two 1.5" drains. The water never seemed to leave the cockpit. You could hose 2" into the cockpit and it would just sit there. An hour later it might be down to 1/2".

Your drain hoses are small, but if you had any head above them they would drain fine.