High 'anti-siphon' loop required with a 'piddle tube'?

[Bilgediver]

I'm still genuine confused as to why such a large height above w/l (Beta's 50cm vs 30cm) is needed where a loop vents high up elsewhere. But if it is simply a matter of headroom added as a caution when a valve/vent is involved, I'd take that!

The bottom of the antisyphon loop where the piddle pipe connection is must be at a height where it is above seawater level even in a damaged boat situation also while listing even. Something amateurs ignore. The piddle pipe has to be on top of that and is part of the antisyphon loop. Without it the antisyphon loop will continue to Syphon so is no longer an antisyphon loop and serves no function.

These became necessary on many boats when lower height Nanni Beta and newer Volvo engines went into boats replacing the other old Volvo's and Bukh. The whole system has to be studied from engine to transom. One boat here fitted the water trap high up behind the engine not realising the danger.

The anti Syphon piddle pipe does not perform that function without the antisyphon loop. They go together like peaches and cream. Attached to the engine it becomes just an indicator . You are doing the best thing by making your own judgement as only you can find the relative heights of the components in relation to the normal and highest expected sea water level and judge the best solution.

 

[PaulRainbow]

The first diagram really deals with the question ”can I get away with installing no AS device at all?”

The OP has already stated "Bear in mind also have a high rise exhaust mixer" so he's subject to the 30cm, not 50cm.

 

[dankilb]

Thanks all. It's not top of the jobs list yet - but in a couple of weeks, I should have an update.

I'm now weighing my options between a '30cm+' setup mounted aft or replacing the full-height loop under the bridgedeck. If I can get something neat like @alahol2's mounted aft, with enough height as a safety margin for extreme conditions, I'd be happy.

But the advice seems to be, unless you're 100% confident you'll be in the Beta 30cm 'figure 15' category, there's a need for both a siphon break and some sort of loop to achieve a 'safe' height (whether 50cm or not!).

 

[BabaYaga]

The OP has already stated "Bear in mind also have a high rise exhaust mixer" so he's subject to the 30cm, not 50cm.

The OP is subject to the 30 cm guide line if he wants to avoid having to install a vented loop. But he doesn’t meet the required height between WL and injection point, he only has 10 cm.
Therefore he must install a vented loop and so he becomes, in principal, subject also to the 50 cm guide line. The fact that he has a high rise exhaust bend makes no difference. (How do I know? In my boat I have a Beta engine with a high rise bend. I also have a vented loop, which was a necessary installation).
Another question, open for discussion, is if the OP really has to meet the full 50 cm requirement, given his specific installation, as already mentioned upthread.

 

[Lucy52]

I suppose you could ask Beta Marine, I guess they might know.

 

[Daydream believer]

I suppose you could ask Beta Marine, I guess they might know.

But then Beta would have to come & ask the forum for the answer