We just got this Pilothouse. Both the 50 gallon holding tank and the maserator pump are under the owner cabin sole and are below the water line. The discharge of the holding tank is also below the waterline, but only by about 3 to 4 inches. Working backwards, the discharge hose from the thru hull valve goes up vertically about 3 feet with a vented loop, then back down to the holding tank. The problem is that water sometimes syphons back to the holding tank and fills it if the valve is not closed. I know the valve should be closed and I do close it when not on the boat. It is in a location that is a real PITA. My guess is the vent in the vented loop is not working. Your expert opinion is greatly appreciated.
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That's easy...keep the thru-hull closed
except when you're actually dumping the tank. The vented loop is working just fine. The only thing a vented loop can do is prevent a siphon from occurring. It will not stop a phenomenon known as "ram water"--water forced up a hose by the pressure of the hull against the water while the boat is underway. It may be a PITA to keep the seacock closed, but that's the breaks. ALL seacocks should ALWAYS be kept closed except when actually in use. That boat builders make that so difficult as to be impossible is indeed a problem. The solution is a shut-off valve inline that IS accessible. Btw, this is not just a powerboat problem.
except when you're actually dumping the tank. The vented loop is working just fine. The only thing a vented loop can do is prevent a siphon from occurring. It will not stop a phenomenon known as "ram water"--water forced up a hose by the pressure of the hull against the water while the boat is underway. It may be a PITA to keep the seacock closed, but that's the breaks. ALL seacocks should ALWAYS be kept closed except when actually in use. That boat builders make that so difficult as to be impossible is indeed a problem. The solution is a shut-off valve inline that IS accessible. Btw, this is not just a powerboat problem.
RAM WATER ENEMA
As the new captain of a 190' research vessel in the Gulf of Mexico I experienced the phenomenon of ram water. Upon an orientation of the vessel with the departing captain I was shown a great number of things,when we passed the head the captain said to me "don't use the head in bad weather" and continued the tour.After a few weeks aboard we got into some pretty bad weather, one thing led to another and I had to use the head.The procedure was to open a valve, sit down do your thing, flush and close the valve again.As I sat there reading boats and harbors deep in thought,a wave slapped the hull and I received a 40 degree salt water enema!! Getting the crap scared out of me took on a new meaning!! True story! ED.
As the new captain of a 190' research vessel in the Gulf of Mexico I experienced the phenomenon of ram water. Upon an orientation of the vessel with the departing captain I was shown a great number of things,when we passed the head the captain said to me "don't use the head in bad weather" and continued the tour.After a few weeks aboard we got into some pretty bad weather, one thing led to another and I had to use the head.The procedure was to open a valve, sit down do your thing, flush and close the valve again.As I sat there reading boats and harbors deep in thought,a wave slapped the hull and I received a 40 degree salt water enema!! Getting the crap scared out of me took on a new meaning!! True story! ED.
It ain't ram water....
when the boat is tied to the dock. How do you check to see if the vented loop is working?
when the boat is tied to the dock. How do you check to see if the vented loop is working?
If the loop is above the waterline...
It would be highly unusual for a siphon to start when the boat is at rest, whether the air valve in the loop is working or not. If the air valve isn't working, it would only happen if ram water had already started the siphon, and in a 1.5" hose it would fill the tank pretty rapidly. If you're paying ANY attention at all, you'd almost certainly see your tank overflowing out the tank vent while you're aboard if you spend the night, and you'd see that before you'd see water backing up into the bowl. So I suspect the problem may be at the other end of the system--the head intake. Water outside the boat will always do its best to seek its own level inside the boat whenever it can find an opening that will let it. If the toilet bowl or any part of it is the below the waterline, and if there's no loop in the head intake, it's not uncommon for water to fill the tank through the toilet if you leave the head intake thru-hull open. It'll definitely fill the bowl to the waterline...and if the rate of seepage out of the toilet is slower than the rate the water is rising, it can overflow the bowl. In fact, leaving head seacocks open while away from the boat is the #1 cause of boats sinking in their slips. Before I can tell you how to fix that, I need know what kind of toilet--manual or electric. In answer to your question about how to know whether the air valve is working...remove it and inspect it. Air valves can get clogged up with salt and waste and need periodic cleaning. If it's beyond cleaning, replace it.
It would be highly unusual for a siphon to start when the boat is at rest, whether the air valve in the loop is working or not. If the air valve isn't working, it would only happen if ram water had already started the siphon, and in a 1.5" hose it would fill the tank pretty rapidly. If you're paying ANY attention at all, you'd almost certainly see your tank overflowing out the tank vent while you're aboard if you spend the night, and you'd see that before you'd see water backing up into the bowl. So I suspect the problem may be at the other end of the system--the head intake. Water outside the boat will always do its best to seek its own level inside the boat whenever it can find an opening that will let it. If the toilet bowl or any part of it is the below the waterline, and if there's no loop in the head intake, it's not uncommon for water to fill the tank through the toilet if you leave the head intake thru-hull open. It'll definitely fill the bowl to the waterline...and if the rate of seepage out of the toilet is slower than the rate the water is rising, it can overflow the bowl. In fact, leaving head seacocks open while away from the boat is the #1 cause of boats sinking in their slips. Before I can tell you how to fix that, I need know what kind of toilet--manual or electric. In answer to your question about how to know whether the air valve is working...remove it and inspect it. Air valves can get clogged up with salt and waste and need periodic cleaning. If it's beyond cleaning, replace it.
it's a Raritan electric, but.....
I don't remember what model it is (the boat is new to me). It has a valve so it can flush with fresh or salt water. It is currently set for fresh water flush. Even when the tank indicator (the one that has lights, empty, half and full) shows full, the bowl is not full.
I don't remember what model it is (the boat is new to me). It has a valve so it can flush with fresh or salt water. It is currently set for fresh water flush. Even when the tank indicator (the one that has lights, empty, half and full) shows full, the bowl is not full.
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