[C320-list] antisiphon valves

[Scott Thompson]

The purpose is to to create a "vented loop" above the water line in 
order to prevent a siphon forming when the associated system isn't in use.

The vented loop in the cockpit locker is for the engine cooling system 
and is in a loop between the engine heat exchange and the exhaust elbow. 
  Without this vent it's possible that when you shut down the engine, 
cooling water could continue to flow due to siphon action from the 
exterior of the boat through the raw water pump and heat exchanger into 
the exhaust elbow and muffler.  Without pressure from the engine exhaust 
to clear the muffler, this could eventually cause the muffler to fill 
with water, possibly allowing water to back up through the exhaust elbow 
into the engine itself, which obviously is not a good thing.

The one for the head is intended to prevent flooding the boat from water 
siphoning through the head pump into the bowl and overflowing.  The 
other one in the head cabinet is for the shower sump pump, where water 
normally flows out of the boat, but could reverse due to siphon action.

Scott Thompson
Surprise, 653

harold brown wrote:
> Thank for the information. Mine are now screwed down
> tight they were all open (including the one for the
> engine). Funny the owner's manual maken no mention of
> it. What is the purpose of having the vented valve in
> the first place? Jim Brown
> --- Quentin Murphy <qmurphy at sympatico.ca> wrote:
> 
>> These should be screwed tight.  Some 320s also have
>> another anti-siphon
>> valve (engine) in the main cockpit locker.  Mine
>> loosened last year and
>> caused the aft cabin berth (including the bedding)
>> to get a good soaking.
>> It took months to get the space under the locker dry
>> and every time the boat
>> heeled, it re-wetted the berth.  Not too pleasant!
>>
>> Quentin Murphy
>> Celtic Knot #667
>>
>> -----Original Message-----
>> From: c320-list-bounces at catalina320.com
>> [mailto:c320-list-bounces at catalina320.com]On Behalf
>> Of harold brown
>> Sent: July 4, 2007 3:45 PM
>> To: c320-list at catalina320.com
>> Subject: [C320-list] antisiphon valves
>>
>>
>> Probably a dumb question but are the screw down caps
>> on the 2 antisiphon valves in the head cabinet
>> supposed to be screwed down or left partially open?
>> Jim Brown     Desafinado
>>
>>
>>
>>
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