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Keeping bags from auto-draining through vent lines


Intense

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As title says, how are you guys prevent auto-drain.

My set-up now is just a straight section of tube from the top of the bag to the thru-hull on the side of the boat. No loops, check valves, or other doo-hickeys.

Although, I don't see how either would help. The loop would be completely horizontal by the time the bag was full. And a check valve would only slow down the auto-draining, but not stop it....

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Run the vent and drain lines to the opposite side thru hull. My vent and drain lines are teed on the same side of the boat so that only one line is run to the opposite side. Works perfectly.

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As title says, how are you guys prevent auto-drain.

My set-up now is just a straight section of tube from the top of the bag to the thru-hull on the side of the boat. No loops, check valves, or other doo-hickeys.

Although, I don't see how either would help. The loop would be completely horizontal by the time the bag was full. And a check valve would only slow down the auto-draining, but not stop it....

We have great success with a check valve in the vent line, to stop passive draining. The next best thing, is to replace a straight thru-hull with a 90 thru-hull, which we use when building a ballast install from scratch.

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Are you sure the water is draining from your vent lines? I just had the same issue with my rear bags draining. My issue was the drain lines, not the vents. I have verified this by putting a couple of ball

valves on each drain line. When these are closed the bags do not drain. I bought a couple of cheapish plastic ones from Lowes that work great. My vent lines are ran just like yours...straight from top of bag to

vent thru hull. Double check to make sure if it's your vents causing the issue. Someone suggested plugging the thru hulls with corks which would make it easy to find the culprit.

Good luck.

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Are you auto-draining when listing the boat or when the boat is flat.

If when listing, just vent to the opposite side of the boat. Check valve isn't going to help you, since either it will keep you from venting at all or only keep air/water from coming back in the vent line.

If draining while flat (assuming rear locker bags), you can:

- Make sure the top of the vent line sits higher than the top of the bag when full

- Vent towards the front of the boat, as it will be sitting higher up there.

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How would a check valve on the vent line prevent draining?

The right style of check valve will require a slight amount of pressure to off seat and allow flow. That pressure is present when the sac is filling. When the fill flow stops, the pressure in the sac drops, and the check valve seats. The force of the passive draining is not enough to foo seat the check valve.

Crossing the vent lines work just fine, but requires both sides to be done in order to have a fee thru-hull for each side to cross to. The cost of the hose needed to cross both sides, is about the same 2 check valves.

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