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Old 01-03-2013, 09:41   #1
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Siphon Break Needed?

I have a Siphon break (Scot Pump VL 10) mounted way above waterline , between our Raw water strainer and our water pump">raw water pump; for the Heat exchanger/ cooling system.
Have heard from a few people this is not needed. Our stainless siphon break is starting to weep and I either need to replace it or eliminate it.

The Forespar Marelon ones are more for sanitation and need a pump before them. The type I have are not easy to find, but if not neeeded then why replace it , I could just bypass.
Any advice would be great!
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Old 01-03-2013, 09:44   #2
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Re: Siphon Break Needed?

I did not think you are supposed to have a siphon break before the engine just after.
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Old 01-03-2013, 10:04   #3
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Re: Siphon Break Needed?

Here's how it should be set up!





OR........

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Old 01-03-2013, 10:11   #4
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Re: Siphon Break Needed?

A siphon break (vented loop) should not be used in a suction hose as it is designed to let air into the line. This reduces the ability of the pump to create a vacuum and suck water. Siphon breaks should only be used on the discharge side of a pump.
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Old 01-03-2013, 11:00   #5
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Re: Siphon Break Needed?

Quote:
Originally Posted by HopCar View Post
A siphon break (vented loop) should not be used in a suction hose as it is designed to let air into the line. This reduces the ability of the pump to create a vacuum and suck water. Siphon breaks should only be used on the discharge side of a pump.
This is what I thought, I couldnt understand why there is one where it is. Our exhaust elbow, and most of the hose is above waterline, so there is no suction or vented loop on that side, could that make a difference? I cant see how it would?
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Old 01-03-2013, 18:06   #6
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Re: Siphon Break Needed?

I think I would have a siphon break if there was even a question about the exhaust going downhill from the engine. In big seas who knows what angle your exhaust might be. I cannot think what disadvantage a siphon break could have in the heat exchanger output line. As for the the snifter valve clogging, leave it out. Run a small hose ovbd. Incidentally, if you place the thru hull for the vented overboard loop in a nice place, it lets you check on your water temp etc. with your fingers, very nice feature.
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Old 01-03-2013, 18:16   #7
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Re: Siphon Break Needed?

Quote:
Originally Posted by Dulcesuenos View Post
I have a Siphon break (Scot Pump VL 10) mounted way above waterline , between our Raw water strainer and our raw water pump; for the Heat exchanger/ cooling system.
Have heard from a few people this is not needed. Our stainless siphon break is starting to weep and I either need to replace it or eliminate it.

The Forespar Marelon ones are more for sanitation and need a pump before them. The type I have are not easy to find, but if not neeeded then why replace it , I could just bypass.
Any advice would be great!
The preferred position for a siphon break in a raw water feed circuit is between the raw water pump and the heat exchanger. Works every time.

FWIW...
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Old 01-03-2013, 18:24   #8
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Re: Siphon Break Needed?

I think to have a vented loop before the heat exchanger it would to have been in the original design of the engine. In something like a Perkins say, the cooling water plumbing does not become accessible until after the heat exchanger. It does sound like a better system though, maybe.
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Old 01-03-2013, 19:22   #9
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My PO did that on the head intake: siphon break before the pump. But because that caused the head to not flush he simply plugged the little leak in the siphon break. Hilarious.
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