EXTRA SIPHON BREAK

[MAURICE]

Hi
I am thinking of adding a second siphon break in the raw water cooling pipe. At the moment i have a Volvo anti siphon break and wish to install a second vetus type as an extra precaution.
Does any one foresee a problem with this

 

[pvb]

Why??

Extra precaution against what? If you check/clean the Volvo one regularly, you won't have any problems. It's not rocket science! Who says the Vetus one wouldn't fail? Whatever next - maybe a second engine as an extra precaution?

 

[MAURICE]

Re: Why??

The reason is that ive had water get back into the engine which was very costly not to mention inconvenient. The device failed within a year which is volvo recomended service interval. All it needs is a small bit of grit to get stuck and the device is useless. At least with a second you have a second chance. It seems that a reliable diesel engine is dependant on a small rubber flap with a hole in it. Apparently this problem is more common than we are led to believe. In Spain this year 17 boats have suffered the same problem.

 

[ccscott49]

Re: Why??

I have a vetus water trap on both my engines, with a high rise water injection manifold and a high bend from outlet to water trap, never had a problem, nor have I heard of any problems lately, I would have a close look at how the system is configured, rather than putting another water trap in, or "anti syphon device", not really sure about this, as the pipe would have to be full of water to cause a syphon, (which it isn't) as in a toilet for instance, I've never come across ths type of thing before and I guess you really mean a water trap. IMHO

 

[philip_stevens]

Re: Why??

If you are worried that the Volvo one will or may fail again, fit the Vetus type that has a small tell-tale "pee" over the side.
Fit it relatively high up (so there is no chance of water being syphoned back in) and when the engine is switched off, the pee-ing stops and water drains out of the tell-tale pipe from the syphon break to the overside outlet.
I fitted one to my last boat, and never had a problem with water getting back to the engine. I also fitted a Vetus water trap and swan neck.

regards,
Philip

 

[david_bagshaw]

you could always convert the existing syphon break to a pee over the side type, muchmore reliaable anyway, wont get stuck, or drip inside.

David
<A target="_blank" HREF=http://www.euroboating.net>http://www.euroboating.net</A>

 

[andy_wilson]

Must remember...

... to fit my first one.

 

[dickh]

Re: Why??

I replaced a bunged up anti-syphon trap with a Vetus with the 'valve' as this was recommended for sailing boats, the 'pee' type was for motor boats - why I'm not sure, perhaps because there is more water flow? I also repositioned it as high as possible in an accessible place - before I did not even know it existed apart from the dribble from the valve...
It's fitted in the pipe from the Jabsco pump to the engine, other people say it should be in the pipe from the seacock to the pump - which is right?

dickh
I'd rather be sailing...

 

[ccscott49]

Re: Why??

The jabsco pump iks a one way valve anyway, the water cannot get through it without it turning, what does this anti syphon valve do, stop the water syphoning into the engine, exhaust or what, I don't understand, sorry. I dont have any. I thought we were talking about water coming back up the exhaust.

 

[dickh]

Re: Why??

I understand it is to stop water being syphoned into the engine when sailing and heeled, it will syphon past? the jabsco pump and fill up the water trap and then back into the engine - as I say mine is fitted after the pump, some seem to be fitted before the pump(which makes more sense), there was an article in one of the mags recently about this, it is a problem on modern shallow hulled craft where the water injection elbow is too low and is below the heeled waterline - cured by fitting a riser to the exhaust. I'll try and find out more tonight. It is certainly a recommendation by V**v*...

dickh
I'd rather be sailing...

 

[pvb]

Volvo\'s recommendation...

Volvo recommend that the vacuum valve should be fitted between the seawater pump and the heat exchanger. (This was part of the rules for the Volvo Ocean Race apparently). The valve is designed to prevent water being siphoned into the exhaust when the engine isn't running - it is possible for water to bypass the impeller in the seawater pump.

The Volvo vacuum valve is inherently a very simple and reliable device. If it's properly assembled (ie with the rubber disc and the metal washer in their correct positions) it's difficult to see how it could fail. However, to assemble it properly, it's best to turn it upside down. Most people can't be bothered to dismount it to do this, so problems do sometimes occur.

 

[JerryHawkins]

Correct position

The anti-siphon valve should be fitted after the water pump, so that it is in the pressure side of the system. The valve-type (rather than the "pee-overiside" type)relies on pressure to keep it closed. If you fit it before the pump it will be on the suction side and the valve will open and draw in air! It should only open when the pressure drops (i.e the engine stops) to cut any siphoning action.

Cheers,

Jerry

 

[Strathglass]

Re: Correct position

I have fitted the Vetus "pee-overside" type in the exhaust bend. I then have a T in the vent pipe.
One rises about 7 inches then gradually tapers down about 10 inches and comes out in the cockpit just 3 inches above one of the two 60mm cockpit drain ports.
The second outlet from the T is taken directly to the deep sea seal. This then provides automatic bleeding of the deep sea seal when launching when launching and lubrication of the seal when the engine is running. This gives me a minimum maintainence system.
Iain