Sailors, I have a stupid question. How does the water drain from a sink through the hull is there a type of ball valve that lets water out but not in what is this called?
sink drain through hull
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Standard through-hull
On my boat the galley sink through-hull is larger than the others (1-3/4" inner diameter). I assume that is to let food particles out without clogging the drain. Other than that it is a normal straight-though through-hull. The water will only come in as far as the waterline, again on my boat this is less than a couple of feet. The sink is several feet above the waterline. I imagine the venturi effect of moving in the water would actually suck out any water in the line while the boat is in motion.
On my boat the galley sink through-hull is larger than the others (1-3/4" inner diameter). I assume that is to let food particles out without clogging the drain. Other than that it is a normal straight-though through-hull. The water will only come in as far as the waterline, again on my boat this is less than a couple of feet. The sink is several feet above the waterline. I imagine the venturi effect of moving in the water would actually suck out any water in the line while the boat is in motion.
Lets it in
I am pretty sure it just lets the water in, thus the need for double hose clamps on any of these through hulls. Pull the hose and open the through hull and see - just make sure you can shut it again before it sinks the boat. I guess you could install a backflow preventer...
I am pretty sure it just lets the water in, thus the need for double hose clamps on any of these through hulls. Pull the hose and open the through hull and see - just make sure you can shut it again before it sinks the boat. I guess you could install a backflow preventer...
Don't install a one way valve
The drain is not a pressurized system and relies on the 6"-12" of sink drain to waterline distance to force the water out of the boat. That is less than 0.5 psi with the sink completely full. A one way valve will not open under that low a pressure so you will have no valve at all.
The drain is not a pressurized system and relies on the 6"-12" of sink drain to waterline distance to force the water out of the boat. That is less than 0.5 psi with the sink completely full. A one way valve will not open under that low a pressure so you will have no valve at all.
Gravity and Suction.
The through the hull opening is usually under the water line and any water draining down will seek that line. Now when the boat is in motion the water rushing across the opening of the through the hull creates suction which will help it drain. You will also find that water can come up the drain, when the boat sinks down into a wave the water level will rise. We sail with our drain open and you can hear it gargle as the boat moves up and down. as far as your question any type of check valve that would limit the direction of water flow should not be used in a sink drain as it would quickly become clogged. Make sure your drain hose is good and that you have double clamps in them. If you are going to be away from the boat for an extended time just close the valve. Have a story about drain valves. In 2004 as I was getting our h27 cherubini ready for a hurricane heading our way I went to close the drain valve and it just crumbled in my hands. It was an original gate valve and the worm just came out with the gate and all. Needless to say water was pouring in. I placed the gate back in the valve and pushed it in by hand until the water slowed to a trickle. I was now in a pickle as the nearest haulout facility was 12 nm away and it was like 5:00 PM and the storm was getting closer. I scraped at the top of the valve and the rest of the pieces started coming out. I realized the body of the valve was sound and the top thread was good so I took a measurement and ran down to Home Depot where I got a PVC plumbing plug of similar size. I stuffed the gate into the valve and placed a plstic bag behind it and threaded the cap on. The following day after the storm had gone through went to check on the boat and it was dry as a bone. Actually that cap stayed there for a couple of months afterwards.
The through the hull opening is usually under the water line and any water draining down will seek that line. Now when the boat is in motion the water rushing across the opening of the through the hull creates suction which will help it drain. You will also find that water can come up the drain, when the boat sinks down into a wave the water level will rise. We sail with our drain open and you can hear it gargle as the boat moves up and down. as far as your question any type of check valve that would limit the direction of water flow should not be used in a sink drain as it would quickly become clogged. Make sure your drain hose is good and that you have double clamps in them. If you are going to be away from the boat for an extended time just close the valve. Have a story about drain valves. In 2004 as I was getting our h27 cherubini ready for a hurricane heading our way I went to close the drain valve and it just crumbled in my hands. It was an original gate valve and the worm just came out with the gate and all. Needless to say water was pouring in. I placed the gate back in the valve and pushed it in by hand until the water slowed to a trickle. I was now in a pickle as the nearest haulout facility was 12 nm away and it was like 5:00 PM and the storm was getting closer. I scraped at the top of the valve and the rest of the pieces started coming out. I realized the body of the valve was sound and the top thread was good so I took a measurement and ran down to Home Depot where I got a PVC plumbing plug of similar size. I stuffed the gate into the valve and placed a plstic bag behind it and threaded the cap on. The following day after the storm had gone through went to check on the boat and it was dry as a bone. Actually that cap stayed there for a couple of months afterwards.
Backflow preventor
Although the sink drain does not incorporate one (as per previous posts) to answer your question a one way valve is called a backflow preventor or check valve
Although the sink drain does not incorporate one (as per previous posts) to answer your question a one way valve is called a backflow preventor or check valve
The galley sink drain on our boat is ...
directly connected to a seacock. I always close it when away from the boat, but leave it open while cruising. It is well above the water line in most all heel points except when greater than about 60 degrees.
Terry
directly connected to a seacock. I always close it when away from the boat, but leave it open while cruising. It is well above the water line in most all heel points except when greater than about 60 degrees.
Terry- Status