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Old 25-12-2018, 08:00   #1
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Location: New Haven, Connecticut, USA
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Need a third hole for flexible water tank

I have a 52 gal plastimo water tank that Iíve been using for 7 years and very happy with it not leaking or chafing. However it only has an inlet and an outlet, it does not have a vent for overflow of air, which creates a problem because air gets in there and the tank is now bloated with half air half water.

Is it possible to add another hole to it so it can vent? How should I go about cutting it? Inserting a barbed fitting in there and sealing it? Or is there a trick I can do with the inlet to create a vent?
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Old 25-12-2018, 08:51   #2
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Re: Need a third hole for flexible water tank

As water is drawn out of the tank, the tank SHOULD collapse to "hug" what's in it. But if that's not happening, try opening the deck fill cap to let air escape.


p.s. This should works for a water tank because the inlet fitting is (should be) at the top of the tank. It doesn't work for waste tanks because the discharge pickup--fitting or diptube--is at the bottom of the tank.
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Old 25-12-2018, 10:53   #3
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Re: Need a third hole for flexible water tank

We have similar flexible water tanks and do have short vent lines installed in the tops of the tank, fitted with hose-end fittings that have a cap on them. This was the prior owner's solution to air having gotten into the tanks and it does work. As an alternative, however, one can also close the discharge line (which should have a valve in it to isolate the tank) and use a shop vac on the fill line to suction out the air in the tank, which will collapse as it is evacuated. Ideally, one shouldn't need a vent but as air is often dissolved in a turbulent water flow, it will come out of solution within the tank as the water "rests" and one will, eventually, need to evacuate it to maintain the tank capacity.n If, however, you do wish to install a vent, look (click on) here. (Use the small fitting.)

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