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Old 27-04-2017, 01:59   #1
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cooling intake double use

Hello
Is there anything that stops me from attaching a y-connection to the intake of cooling water for the engine and then take my dishwashing water from the same thru-hull-fitting? Would be very convenient - looking to reorganise my chaotic plumbing...

Kindly
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Old 27-04-2017, 02:13   #2
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Re: cooling intake double use

Ha ha! Perfect! Why not get it to do the washing also? I would just want to be sure that the gauge of the hose was sufficient to take care of the full flow so as not to have pressure in the wrong direction back to your engine
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Old 27-04-2017, 02:40   #3
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Re: cooling intake double use

Not as straight forward as it seems.
Part of the raw water cooling circuit can be low or negative pressure. Specifically from the through hull to the raw water pump.
It may (depending on waterline height) decide its easier to suck air from the dishwasher side rather than cooling water.....
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Old 27-04-2017, 04:23   #4
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Re: cooling intake double use

Thanks for your replies.
I might have mislead you, I am talking about sharing the intake for the engine cooling water with the hose that leads to the manual pump that pumps sea water to my sink. My 1976 OE29 does not have a dishwashing machine onboard.

So, both of the hoses would have negative or no pressure and I'm assuming the membrane pump will not let air through in the wrong direction.

I might just give it a try and be careful.

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Old 27-04-2017, 08:38   #5
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Re: cooling intake double use

The Island Packet 27 has a single seacock for both the the engine raw water intake and the head intake (a simple T), which seems to work well. The only other seacock is the head (now holding tank > macerator) discharge, which I keep closed. I like the idea of limited holes in my hull and only one seacock to regularly worry about.
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Old 27-04-2017, 08:46   #6
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Re: cooling intake double use

As it came from the factory, my IP 38 had both heads drawing water from the engine thru hull, after the strainer, never caused a problem
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Old 27-04-2017, 08:55   #7
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Re: cooling intake double use

Where did you get the idea that there is no water pressure at the through hull? Typically your through hull is a few feet below the waterline. You can measure the pressure by removing in hose, opening the valve and measuring how high the water squirts. Putting a 'y' before your pump might create a condition where your sink hose gets drained forcing you to prime the pump after any engine use and making it inoperable when the engine is running. Possibly a one way valve would avoid the draining but thot the pressure differential.. The pressure pulling the coolant is a lot more than you can create on a manual sink pump. It might avoid the issue if you could place your valve after the engine intake pump but then it only works when the engine is running and you need a faucet not a sink pump. I suspect you will drop the idea or go with a dedicated through hull.
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Old 27-04-2017, 08:58   #8
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Re: cooling intake double use

I've had mine set up that way for over 10 years no problem. I have an 1 1/2" intake with a Y down to 3/4 for the sink. It goes to an electric water pump. Normally don't do dishes under way but have on occasion with no increase in engine temp. It really never runs any length of time just short spurts.
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Old 27-04-2017, 08:58   #9
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Re: cooling intake double use

I did this for an appliance once. I found when the engine was running there were air bubbles being drawn into the engine intake. It made me nervous so I removed it. The problem is you may lose your prime to the engine making the impellor suck a prime every time. It all depends on the levels of things attached I guess.
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Old 27-04-2017, 09:16   #10
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Re: cooling intake double use

Quote:
Originally Posted by Neptune's Gear View Post
Not as straight forward as it seems.
Part of the raw water cooling circuit can be low or negative pressure. Specifically from the through hull to the raw water pump.
It may (depending on waterline height) decide its easier to suck air from the dishwasher side rather than cooling water.....

What he said. If you were going to do this so as not to have another through hull I would put a Y in the line for one or the other but not both at the same time
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Old 27-04-2017, 09:33   #11
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Re: cooling intake double use

The foot pump's intake valve will prevent backward flow, that is unless its busted, you can't pull air back through the hose, but adding a check valve would now double the protection if you desired
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Old 28-04-2017, 03:13   #12
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Re: cooling intake double use

My previous C&C 33 took the wash down intake from the engine inlet after the strainer. I did add a check valve on the wash down side to prevent any pump failure from causing an air leak into the engine, and because the engine suction kept un-priming the wash down side.
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Old 28-04-2017, 03:48   #13
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Re: cooling intake double use

I have the set-up you describe. Sea water foot pump at the sink.


Works fine since 2001. (all year liveaboard )


Never had a problem using the foot pump while the engine was running.


When installing I put a non return valve in the foot pump line just behind the Y.
Proved useless. Non return valves get stuck in seawater after just some days. Small barnacles are living in it.


Do remember that when the 0,7 mm thick membrane of the foot pump breaks the sea will enter your boat. Not a big problem if you are on board, water just trickles.
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Old 28-04-2017, 08:28   #14
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Re: cooling intake double use

Regardless of how many have got away with it, it is generally not a good idea to share an intake of a critical nature, such as engine cooling.
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