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Old 11-14-2013
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Dumb question about holding tank structure

I have always ignored the mechanics of how the tank gets emptied. Just open deck plate and insert pump-out nozzle, or turn on macerator and let it pump, assume it works fine What i am curious about is the piping, or lack thereof inside the tank. The fittings for both the deck pump-out and the macerator (I have one of each on the tank) are on the top of the tank. Is there an interior pipe that reaches down towards the bottom of the tank to pick up the lower levels off luid, or is it emptied just with pure suction applied at the top opening? Inquiring minds finally want to know.
Mike sullivan
1985 Marshall 22 catboat
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Old 11-14-2013
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Re: Dumb question about holding tank structure

Yes, if the pump-out fitting is at the top then you have an internal dip tube to suck it out from the bottom. Sealand makes a popular kit for this.

It's my personal preference for how to do it, then you never have a flexible hose with sewage sitting in it.
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Old 11-14-2013
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Re: Dumb question about holding tank structure


One other thing you should know about your holding tank is how the vent is plumbed. It is very important to keep the vent clear or the emptying process could damage the tank and spill nasties all over your boat.
Tim R.
Out cruising
1997 Caliber 40LRC

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