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post #1 of 8 Old 09-18-2011 Thread Starter
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vented loop question

I have a Groco bronze anti-siphon vented loop on the raw water line of my exhaust cooling system on the Yanmar. (See image below)

The other day I saw that a little water was tricking out of the small hole on the top of the bronze cap. I removed the vented loop to clean it as best I could, but it now leaks even more. I can't find a replacement part in Brazil, so I'm left with 2 options if I want to use the boat over the next months (as I wait for a replacement from abroad):

1) Repair the vented loop. Does anyone know how to service these things? Any advice for me? I tried to clean the rubber diaphragm, but it doesn't look like one can take the whole thing apart to get at the guts inside to effect a proper repair.

2) Remove the bronze cap and anti-siphon diaphragm on the top of the vented loop and attach a hose to vent overboard. This is what Groco says: "Cap is threaded 1/2" NPT to accept a barb fitting if you wish to vent overboard.". Also, my Nigel Calder book mentions the same option of attaching a hose to the top of the vented loop and bringing the hose to a place well above the waterline to vent. Calder seems to say that you remove the diaphragm before attaching the hose. This option seems the best for me as it should be the most reliable way to get a siphon break without all the fussy problems of delicate diaphragms and valves. Is it as simple as it seems to be? Do I just unscrew the top, pull out the guts and screw in a bronze hose barb and run a hose to a higher location to vent? How high above the waterline does it have to be and does it have to exit the boat or can the hose terminate inside a locker?

Thanks in advance,

Mark
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post #2 of 8 Old 09-18-2011
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Yes its as simple as you descibe. But you need to vent overboard as water (and exhaust gas!!) can flow out of the vent and you don't want that running into a locker.
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post #3 of 8 Old 09-18-2011
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sounds like a bad flapper or maybe an uneven sealing surface

for service or help

http://www.groco.net/SVC-MAN-07/Sec1...nted-Loops.pdf

there is a phone number at the bottom of the page
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post #4 of 8 Old 09-18-2011 Thread Starter
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Thanks very much for the replies. I'll see if I can service the vented loop before going the vent hose route (which involves routing to an exit hole in the cockpit).

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post #5 of 8 Old 09-18-2011
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I agree with JimsCal that it needs to be vented overboard. Mine is vented to a thru-hull just below the toerail and at cruising rpm will weep a little water occasionally.
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post #6 of 8 Old 09-18-2011
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On our previous boat the vented loop was run into a cockpit drain line/thruhull above the waterline.. I imagine it weeped a bit all the time but we never noticed, of course. In any event this arrangement should still function as an anti-syphon and avoids external weeping and any staining that may eventually result.

Ron

1984 Fast/Nicholson 345 "FastForward"

".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
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post #7 of 8 Old 09-18-2011
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On some boats the vent is placed in the cockpit over a drain so as to act as a visible telltale that cooling water is flowing. I believe Calder mentions this as well. Strikes me as a good idea.
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post #8 of 8 Old 09-28-2011 Thread Starter
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Just a quick update in case someone else finds him/herself in the same position. I called the Groco people (thanks Cruisingdream) and bought the repair kit for the vented loop. They sell the diaphragm assembly (rubber parts). It's a bit spendy at 25 bucks, but it should bring the bronze vented loop back to new.

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