Somebody ‘splain me this?

[Leadfree]

The below video is of a sink leak. I’m trying to figure out how the sink would drain to begin with. Please enlighten me…

[PippaB]

Presumably the bottom of your sink is at, or just barely above your waterline. Water finds its own level, so when you get water in the sink it will drain down until it reaches the level of your waterline. Given the leak, that is somewhere in the basket you just installed. If your sink drains entirely then the waterline is below the sink bottom, and above the threads where your drain elbow connects (and it changes when you heel). That's only an inch or two range, but an inch of head pressure is plenty to bring in a fair amount of water through a hose that size.

[VChild]

When my boat is fully loaded, I have the same issue with the waterline being just barely below the bottom of the sink. It causes several problems. The sink drains a little slower and the gray water has a tendency to hang around and stagnate right at the level of the drain, causing a noticeable smell after a while. Also, the seawater is in constant contact with the stainless steel drain fitting rather than just the hose and causes corrosion there, not unlike what is seen in the above video. The solution I used was to put a Y-valve on the sink drain hose with one outlet going to the normal drain seacock. The other outlet goes to a Rule shower sump pump box I mounted under the sink. It automatically pumps through a check valve to an above waterline thru-hull. I can use either drain route to drain the sink. To keep stagnant gray water or seawater from being right at the drain level, I turn the Y-valve to isolate the underwater seacock and direct the gray water to the sump instead. With it in that position, there is no standing water level in the drain or hose so the sink drains very quickly. When done using the sink for a while, I run a little fresh water to rinse and all goes to the sump and then pumped overboard. Then there is a clean drain and hose with no water sitting in it. No smell, no corrosion of the drain. If using the sink constantly, I save wear and tear on the sump pump and turn the Y-valve the other way. But when done, I switch it back again to rinse and empty it.

[Ken Fry]

Originally Posted by VChild

When my boat is fully loaded, I have the same issue with the waterline being just barely below the bottom of the sink. It causes several problems. The sink drains a little slower and the gray water has a tendency to hang around and stagnate right at the level of the drain, causing a noticeable smell after a while. Also, the seawater is in constant contact with the stainless steel drain fitting rather than just the hose and causes corrosion there, not unlike what is seen in the above video. The solution I used was to put a Y-valve on the sink drain hose with one outlet going to the normal drain seacock. The other outlet goes to a Rule shower sump pump box I mounted under the sink. It automatically pumps through a check valve to an above waterline thru-hull. I can use either drain route to drain the sink. To keep stagnant gray water or seawater from being right at the drain level, I turn the Y-valve to isolate the underwater seacock and direct the gray water to the sump instead. With it in that position, there is no standing water level in the drain or hose so the sink drains very quickly. When done using the sink for a while, I run a little fresh water to rinse and all goes to the sump and then pumped overboard. Then there is a clean drain and hose with no water sitting in it. No smell, no corrosion of the drain. If using the sink constantly, I save wear and tear on the sump pump and turn the Y-valve the other way. But when done, I switch it back again to rinse and empty it.

Sounds like a great system!

[Leadfree]

Thank you, vchild. You describe what I thought would happen: stagnant standing awa a leak point.

The video is emphatically NOT me nor my boat. My sink is well above waterline and I have no experience with how monohull systems work, therefor the question.