Anti siphon valve.

[Bongo]

Could you help me with this please...
In the removable top part, there is a rubber disc, what do I do with it ? is it replaceable and should I be able to blow throu' it both ways ? Boat is Oceanis 350. Penta 2003.
Removed it as it was dribbling. ( ! ) I have read the threads on this but am not enlightened. I await your comments, thanks to all.

Hope pic. uploads...

 

[pvb]

The way it works is like this - when the engine's running, the pressure of the cooling water forces the rubber disc upwards, sealing off the little bleed hole. When the engine stops, the rubber disc can fall back down, opening up the bleed hole, allowing air in to the pipe to break the syphon effect.

The rubber disc is replaceable. You shouldn't be able to blow through it both ways.

Ideally, you should service the valve every year. The instructions are in the Volvo Penta operating manual - see below for an extract. The instructions aren't particularly clear; where it says "Reassemble the valve in the upright position", it actually means upside down (ie 180 degrees different from its normal mounting position).

 

[VicS]

The Volvo ones always dribble dont they?
At least while its dribbling you know that it is not blocked or stuck shut!

 

[pvb]

The Volvo ones always dribble dont they?

Often, but not always!

 

[West Coast]

For me - always!

Replaced it with a vetus unit a couple of years ago - very expensive but works well

 

[Quandary]

Volvo anti syphon valve

It needs to be very clean, assembled very carefully , you must not trap the flap, and not screwed up too tight, it is a bit of a hit and miss operation, but if you persevere you will get it to function perfectly without dripping.

The Vetus ones are a really silly price for a bit of moulded plastic.

 

[Bongo]

Thanks to PVB and all, for the info. My valve has an additional pipe brazed to it, Vetus may be the way to go..more money..at least it's a lovely dry, hot August...to justify the cost.

 

[colvic987]

.at least it's a lovely dry, hot August...to justify the cost.

If only that was true up this way. people have been flooded out this week. 'A country of two halves', comes to mind.

 

[DaveS]

Often, but not always!

When I bought my current boat about 12 years ago the valve dribbled quite a lot. I cleaned it out that and each following winter following Volvo's instructions and it's never leaked since. I think the key point is not to over tighten the nut.