Creating Venturi/aspirator to remove condensate

[tc0nn]

I'm trying to create a venturi type of pump to remove low-volume condensate. Essentially what I am planning on doing is putting a tee in the hose leading away from my 7000 BTU polar bay air conditioner. The tee will have a super small hose leading to the condensate collection tray. Now the only reason I think this is going to work without adding the restriction in the middle of the tee is because my pump sits just before the water is ejected out of the boat basically creating a vacuum through the entire water system on the boat. My reason for putting the pump last in the series of hoses and devices was that if I ever spring a leak, the worst (I'm hoping) it will do is start sucking air through the leak and stop the AC from being efficient. In the event of a catastrophic leak, the pump would burn up but would allow the water to syphon back into the lake. This is a self-priming pump from Home Depot ($69 I think) so the loss of the pump is minimal compared to a hull filling with water due to a leak after the pump.

Can I get a sanity check? Am I missing something?

Wikipedia describes this sort of venturi pump fairly well:
http://en.wikipedia.org/wiki/Venturi_pump

 

[Don S/V ILLusion]

This won't work because you have the system designed backward. Putting the pump downstream of the venturi will prevent the pump from sucking water up from your thruruhull, through the cooling coils and out the boat. All you will do is such air out the venturi until the pumps burns up.

You are on the right track though. Put a centrifugal pump of sufficient capacity below the waterline on the input side of the A/C. This is the standard system.

On the discharge side of the A/C, mount the venturi with the small side plumbed into the condensate pan. The water pressure out of the A/C will create the desired vacuum pulling anything that collects in the pan out with the cooling water.

This is the equivalent of a product commerically marketed called a "condensator" or solething similar but obvioulsy cheaper and similar to what I have on our A/C on which I installed a similar plastic venturi that came with our son's waterbed to empty it.

Cautions: put it on the side of the discharge hose as it exits the boat lower than the pan; add a shutoff valve as you won't need to suck air in heat mode or simply to preclude backflow when heeling.

 

[Ed Schenck]

Great description Don. And exactly right. I have the Mermaid condensator on my boat, what a great device although overpriced. It was a deal when I bought mine in 2000. But what about his concern that a hose or clamp failure could sink the boat, his reason for having it close to the exit? I never have mine running unless I am on the boat so it was never a concern to me.

 

[Don S/V ILLusion]

Great description Don. And exactly right. I have the Mermaid condensator on my boat, what a great device although overpriced. It was a deal when I bought mine in 2000. But what about his concern that a hose or clamp failure could sink the boat, his reason for having it close to the exit? I never have mine running unless I am on the boat so it was never a concern to me.

If I understand your point, in this case, the pump is useless in the location described regardless of whether or not a hose clamp can fail. Point well taken though. The way I look at it, if a hose clamp fails it will be the one located in the worst possible location regardless of where the pump is located. More important, I'm with you on never leaving it running unless I'm onboard

 

[Hermit Scott]

In the event of a catastrophic leak, the pump would burn up but would allow the water to syphon back into the lake.

Unless the clamp is below the waterline. Then it won't matter where the pump is located.