Vetus Anti Syphon on Heads - Help

[shaunksb]

I fitted, a few months ago, an anti syphon loop as I replaced the loo on the new boat.

I gave it a "dry run" at the weekend to check it was working by pouring some water down, opened the cocks and pumped away.

To my embarrassment it spurted water out from the top outlet which consists of a threaded plastic nut with a hole in the top.

The one circled in the pic.

I know I am being a numpty and something basic must be wrong but I'm not sure what to do. The "instruction" for what little they contained are in the bin by now & I can't find a manual on the Vetus site.

Should it have a washer in? I have seen them with an overflow pipe fitted to the top but don't want to go down this route in the Heads.

Can someone help before I turn the boat into a dirty protest cell?



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[CharlesSwallow]

That is the "air introduction valve" and it breaks a syphon when the engine is stopped and the sea water pump stops pumping. YES! it is intended for use in an engine cooling system. Using one in a toilet outlet will result in all sorts of problems due to the constantly varying pressure in the outlet pipe as you pump. Furthermore, deliberately introducing ANY obstructive "ridge" within the outlet is just asking for toilet paper to become jammed , giving you a future of repeated nasty unblockings to look forward to.A better idea for an anti-syphoning loop in a toilet is to simply install enough outlet pipe so that it can be looped up above sea level. This is usually done inside a locker adjacent to the loo. The syphon is broken when the bowl is emptied and a few further pumps introduces air into the outlet which of course goes to the top of the loop.

Chas

 

[VicS]

Yes it should have a one way valve in the top which opens to allow air to enter in order to break the syphon.

 

[shaunksb]

That is the "air introduction valve" and it breaks a syphon when the engine is stopped and the sea water pump stops pumping. YES! it is intended for use in an engine cooling system. Using one in a toilet outlet will result in all sorts of problems...

Presumably an "air introducion valve" is also a "smell exhaust valve" ?

I thought these were a fairly typical fit but on reflection I may be better just taking the thing out.



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[shaunksb]

Yes it should have a one way valve in the top which opens to allow air to enter in order to break the syphon.

This seems to be missing



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[VicS]

This seems to be missing



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Another ( minor) good reason to have a Lavac ... they don't have antisyphon valves ... just a little air bleed on the inlet pipe

As suggested you'd probably get away without but you'd be relying on the outlet valve and the joker valve to prevent back syphoning unless you shut the seacock.

 

[rob2]

I don't think this is an engine anti-syphon valve - the size of hose is totally different. Vetus (and others) do recommend fitting these even where the loop is well above heeled waterline, although I've always had a plain loop and (so far, fingers crossed) no trouble. The basics are that it should be at the top of the loop on the outlet - the water pressure as you pump should close the valve whereas any suction will draw in air, thus not supporting a syphon. On the inlet side a similar valve is available although it is important that it is fitted between the pump and bowl, not between seacock and pump, so that it is in a pressurised line, not one with suction on it.

It is quite possible that the valve has stuck in the open position if it has been in stock for too long. Perhaps others can advise on how to strip it down and get it working, although you should be able to return it for replacement, surely?

Rob.

 

[CharlesSwallow]

I don't think this is an engine anti-syphon valve - the size of hose is totally different. Vetus (and others) do recommend fitting these even where the loop is well above heeled waterline, although I've always had a plain loop and (so far, fingers crossed) no trouble. The basics are that it should be at the top of the loop on the outlet - the water pressure as you pump should close the valve whereas any suction will draw in air, thus not supporting a syphon. On the inlet side a similar valve is available although it is important that it is fitted between the pump and bowl, not between seacock and pump, so that it is in a pressurised line, not one with suction on it.

It is quite possible that the valve has stuck in the open position if it has been in stock for too long. Perhaps others can advise on how to strip it down and get it working, although you should be able to return it for replacement, surely?

Rob.

Don't see how you can tell the diameter from the picture.

With the simple pump of a typical sealoo you cannot expect JUST pressure; there will be some albiet small suction created due to the lack of precision in the valve configuration and the effects of normal wear.

Vetus will of course "recommend" anything they sell! I would not use one since it is unecessary if you always "Dry Bowl", loop the outlet hose sufficiently above the waterline and I certainly DO NOT wish to encourage a habit in the crew of leaving the seacocks open when the loo is not in use - JABSCO recommend NOT doing that!. Then there is the matter of deliberately introducing an obstruction, not to mention the (common) problem that the OP is having. Vetus, in their current catalogue, (which does not contain the product shown, incidentally) advise regular cleaning "to avoid salt build-up which will clog the device".

So why complicate matters and give yourself the possibility of blockages, leakages and seized seacocks due to lack of use?

Chas

 

[rob2]

Don't see how you can tell the diameter from the picture.

Just a question of relative size of hose barb against screw hole... On my engine there wouldn't be room for a panel pin!

I agree, I don't like unneccessary valves - they will always leak at some time. They shouldn't encourage leaving seacocks open, either. I need a drink to get rid of the image of a syphon ocurring whilst sat with three layers incl. oilies around the ankles... an inescapable enema!

Rob.

 

[shaunksb]

Just a question of relative size of hose barb against screw hole... On my engine there wouldn't be room for a panel pin!

I agree, I don't like unneccessary valves - they will always leak at some time. They shouldn't encourage leaving seacocks open, either. I need a drink to get rid of the image of a syphon ocurring whilst sat with three layers incl. oilies around the ankles... an inescapable enema!

Rob.

So the consensus seems to be not to bother with one.

I didn't have one one my last boat for 6 years but I thought as I was replacing the loo, the stopcocks and the hose I might as well go for the belt and braces approach.

It seems I have either lost or not fitted the valve as, as far as I can see, there is just the nut with the hole in it over an exit to the loop. It looks like you could fit a nipple into this set up to take a breather pipe off (as i have seen on one photo) or possibly push a valve into it but without checking with someone who has a "working" version I'm struggling to find what I have missing.

Anyway thanks for the help so far.



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[oceanpilgrim]

vented loop

that is a toilet vented loop, NOT an engine type,there should be a black plastic cap that screws on and in side there is a white rubber valve this sounds like is that is missing,hose size is 1"1/4 or 3/4,try a phone call thay may put one in the post for you

 

[pappaecho]

The survey on Silver Song ( 30 years old) noted that it had not been fitted with an anti siphon loop.
In 30 years never siphoned, hence no loop

 

[NorthUp]

There are two different types of vented loop in the Vetus catalogue, the one you have requires a small bore vent pipe to be connected, discharging overboard (ADS38H), and the one you require (ASD38V) has a non- return valve fitted, which will admit air into the bend and thus break the syphon.

Page 136 of the Vetus catalogue which Google will find for you.

 

[VicS]

Or just click this link Vetus antisyphon valve and then click on it again to enlarge it

 

[CharlesSwallow]

There are two different types of vented loop in the Vetus catalogue, the one you have requires a small bore vent pipe to be connected, discharging overboard (ADS38H), and the one you require (ASD38V) has a non- return valve fitted, which will admit air into the bend and thus break the syphon.

Page 136 of the Vetus catalogue which Google will find for you.

The one shown on page 136 is a different product altogether from the one in the OP.

Chas

 

[Adamastor]

VETUS have got two models of anti-syphon-valve/ vented loop. It's just the style of valve that differs between the models. IMHO, and not just because I'm from the trade (sorry), you need an ASV, but just between the pump and the bowl in the inlet side of the line. That way the syphon is broken, even if the pump is switched to "dry".
I have seen Jabsco valve plates deformed from long-term "dry"setting, and they occasionally fail. Next time you service your heads pump have a look at what happens when you switch between modes: the little rubber and brass megaftah is all that stops vast quantities of (insert choice of Ocean here) flooding up the pipe.

 

[CharlesSwallow]

VETUS have got two models of anti-syphon-valve/ vented loop. It's just the style of valve that differs between the models. IMHO, and not just because I'm from the trade (sorry), you need an ASV, but just between the pump and the bowl in the inlet side of the line. That way the syphon is broken, even if the pump is switched to "dry".
I have seen Jabsco valve plates deformed from long-term "dry"setting, and they occasionally fail. Next time you service your heads pump have a look at what happens when you switch between modes: the little rubber and brass megaftah is all that stops vast quantities of (insert choice of Ocean here) flooding up the pipe.

So what is wrong with turning off the bloody seacocks?

Chas

 

[NorthUp]

The one shown on page 136 is a different product altogether from the one in the OP.

Chas

Correct.....


quote: "I can't find a manual on the Vetus site."

what did the OP do with the one that came out of the vetus box?

 

[VicS]

So what is wrong with turning off the bloody seacocks?

Chas

Nothing is wrong with turning off the seacocks.
it when they are not turned off that the problems can occur.

I know a couple whose boat almost sank during the night while the family were all on board and asleep.
One of the children had used the toilet but had not properly closed one of the seacocks. It is very unlikely that vented loops would have been fitted.

Early the following morning when the owner woke their cool box floated past him. That was when he realised there was a problem.

 

[Tranona]

That is not an engine cooling system anti syphon valve, but a Jabsco toilet hose vent loop. If it is 1 1/2" then it is intended to be at the top of the oultet loop if the loo is below the water line. Also available in 3/4" for in between the inlet pump and the toilet bowl, again if loo is below the waterline.

The instructions on installing a Jabsco toilet will explain how and why they are used. Nothing clever about them.