Theere seems to be a pressure build up in the holding tank (82 H27). It has been diagnosed as a plugged vent. What is the easiest way to open the vent? Andy s/v Barogue
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Peggie Hall/Head Mistress
Check the thru-hull first
That's usually where the clog is. If not, try putting an air horn over the thru-hull and blasting it. That's been known to blow any obstruction out the vent hose. If neither of the above works, you'll have to remove the hose. If that's necessary, I'd just replace the vent hose rather than try to clear it.
That's usually where the clog is. If not, try putting an air horn over the thru-hull and blasting it. That's been known to blow any obstruction out the vent hose. If neither of the above works, you'll have to remove the hose. If that's necessary, I'd just replace the vent hose rather than try to clear it.
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Ed Schenck
Thru-hull.
I guess you mean that little chrome thing Peggy? About six inches below the toerail? I use a piece of wire and almost always find "stuff" in there. But won't the vacuum from the pump-out suck the vent line clear? What about water pressure from your washdown hose?
I guess you mean that little chrome thing Peggy? About six inches below the toerail? I use a piece of wire and almost always find "stuff" in there. But won't the vacuum from the pump-out suck the vent line clear? What about water pressure from your washdown hose?
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Peggie Hall/Head Mistress
No, the pumpout will not clear a blockage
in the vent line or thru-hull. But a blockage will cause the tank to pressurize when you flush the toilet, and the suction from a particularly strong pumpout can implode the tank. (And yes, I do mean "that little chrome thing." It's absolutely essential that the holding tank vent line and thru-hull be kept clear at all times. I doubt if a washdown pump has enough pressure to clear a blocked vent, but if there's enough pressure on the dock, a hose with a nozzle attached MIGHT clear it. Certainly backflushing with a hose each time the tank is pumped will help to prevent a blockage. My advice: replace "that little chrome thing" with an open bulkhead fitting and replace the vent line too.
in the vent line or thru-hull. But a blockage will cause the tank to pressurize when you flush the toilet, and the suction from a particularly strong pumpout can implode the tank. (And yes, I do mean "that little chrome thing." It's absolutely essential that the holding tank vent line and thru-hull be kept clear at all times. I doubt if a washdown pump has enough pressure to clear a blocked vent, but if there's enough pressure on the dock, a hose with a nozzle attached MIGHT clear it. Certainly backflushing with a hose each time the tank is pumped will help to prevent a blockage. My advice: replace "that little chrome thing" with an open bulkhead fitting and replace the vent line too.
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Andy
follow up to Ed and Peggy
I tried a wire (would not go very far) and the dock hose with no luck. I will use a nozzle that will give me a bit more pressure this weekend. I was wondering about compressed air. Can you use too much force? Andy
I tried a wire (would not go very far) and the dock hose with no luck. I will use a nozzle that will give me a bit more pressure this weekend. I was wondering about compressed air. Can you use too much force? Andy
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Peggie Hall/Head Mistress
An air horn sometimes works
It's worth trying, anyway. However, as mentioned previously, the "little stainless thing" that all the boat builders use for vent thru-hulls should all be replaced with open bulkhead thru-hulls. Those stainless thru-hulls are a "universal" thru-hull fitted so they can be used to vent gas tanks--with just a slit to prevent water from contaminated fuel and a screen that acts as a spark arrester. They cause more problems than they solve when used for holding tank vents, because the slit gets clogged very easily, the screen rusts and becomes a trap for dirt, dust, pollen and anything else that gets near 'em. They also contribute to odor because the slit is so small. I hate 'em...but boat builders use 'em on everything--gas, diesel, water and holding tanks.
It's worth trying, anyway. However, as mentioned previously, the "little stainless thing" that all the boat builders use for vent thru-hulls should all be replaced with open bulkhead thru-hulls. Those stainless thru-hulls are a "universal" thru-hull fitted so they can be used to vent gas tanks--with just a slit to prevent water from contaminated fuel and a screen that acts as a spark arrester. They cause more problems than they solve when used for holding tank vents, because the slit gets clogged very easily, the screen rusts and becomes a trap for dirt, dust, pollen and anything else that gets near 'em. They also contribute to odor because the slit is so small. I hate 'em...but boat builders use 'em on everything--gas, diesel, water and holding tanks.
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Bob Miller
More...
My vent has only plugged up once, but I just assumed that it would be the nature of the beast for it to plug up every 5 years or so ( it is now plugged again for the second time in 14 years. I like the idea of replacing the "little chrome thing" but that is not what plugged, in my case. The blockage in my case was the elbow fitting on the tank where the hose connects. It was blocked with corrosion type stuff. I had to take the hose off and clean it out with a screwdriver. Any comment on that, Peggie?
My vent has only plugged up once, but I just assumed that it would be the nature of the beast for it to plug up every 5 years or so ( it is now plugged again for the second time in 14 years. I like the idea of replacing the "little chrome thing" but that is not what plugged, in my case. The blockage in my case was the elbow fitting on the tank where the hose connects. It was blocked with corrosion type stuff. I had to take the hose off and clean it out with a screwdriver. Any comment on that, Peggie?
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