Anti-syphons in the heads

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Independence

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I'm due to replace the heads on a newly purchased boat and have realised there were no anti-syphons fitted when I removed the loo.

Is it good practice to have anti-syphons on both the inlet and outlet pipes?

Thanks
 
Good idea to have on both, but I saw an ASV fitted between the water uptake and the toilet pump recently! Customer couldn't understand WHY his heads wouldn't flush properly!
You have to fit the ASV on a positive-pressure pipe, so you have to put it between the pump and the bowl. Usually toilets have a short bit of hose here, so you'll have to extend it to suit your ASV location.
 
Depends on the type of loo and the installation height. If it is mounted below the WL it is advisable to have one on the inlet loop. However some loos have a "dry bowl" setting and if aways set on this it is not strictly necessary to have one if you always leave it on that setting. The outlet will always be under pressure and should clear to an air break as soon as you stop pumping so should not be necessary. This assumes that there is a loop on both inlet and outlet that is well above the WL on either tack.
 
I depends on how low the toilet is fitted relative to the water level. As the old saying goes, "water will find its own level". It does not flow uphill.

I have fitted a couple of marine toilets but not needed anti-syphon valves on either of them apart from the Lavac which needs an air bleed to function properly.
 
Apart from the functional need in a Lavac - I am not familiar with that very well thought of beast - I thought the main point of a syphon break was to avoid the risk of the sea filling your boat due to back syphoning if you fail to shut the seacocks?

Happy to be corrected and it may not apply on some yachts due to the lay out, but a fellow member found the floorboards awash on his Starlight 35 last summer. He had only popped down by chance to check something mid week so it would have been in big trouble by the weekend. He had never been in the habit of closing seacocks - I gather they were pretty inaccessible - and there was no anti-syphon loop.

There is now.
 
If the toilet goes below the water line either at rest or when heeled then antisyphon loops and valves are a must in both lines . The one in the inlet must be after the pump as another poster mentions. Failure to do this alows water to back flow either through the inlet or outlet if the pump valves or the joker valve starts to leak.
 
[ QUOTE ]
That loo was proberbly a Jabsco with the "Little Lever" left in the wrong position

[/ QUOTE ]

How should it be left ?

However with anti syphon AND seacocks turned off should never be a problem.
 
You speak with great authority and certainty but not much logic.
Pray tell me how the OUTLET, fitted with a large enough loop well above the waterline can syphon back past the valve in the pump? Answer, it can't unless the valve fails. Even if that were to happen the diameter of the pipe would make a syphon very unlikely if it is lead well above the waterline. The inlet on the other hand can if there is no valve closing device on the pump as the valve will naturally open in the inward direction and it is smaller bore pipe , but if there is a dry bowl closer and it is always left shut this can't either. It is good practice to fit one on the inlet regardless but not as I said, strictly necessary with a high enough loop if you have a dry bowl closer.
 
<span style="color:white">. </span>
Your best defense is to keep the seacocks shut when the heads are not in use.

We don't have anti-syphon loops on the inlet or outlet, preferring to shut the seacocks - which are readily accessible. The big advantage is that our outlet pipe is 2" long, meaning easy pumping and no 5ft loop of [--word removed--]-encrusted pipe hanging around.

The inlet is the most dangerous allegedly as the valve on that is not as reliable as the joker valve on the outlet. A good compromise would be a loop with anti-syphon valve on the inlet and a Jabsco twist and lock with no loop at all on the outlet. The twist and lock mechanism means the shaped piston is locked in the outlet acting as a back-up to the joker valve.

However, in the end you need to do what works for you and makes you feel safe.

- W
 
As my Jabsco is below the waterline I fitted new pipe and vented loops according to the installation instructions HERE (2mb PDF)

I wouldn't trust crew members to remember to open/close the sea valves properly.

From the manual:

If the toilet is connected to ANY through-hull fittings, and if the rim
of the bowl falls below the waterline, water may flood in causing the
craft to sink, which may result in loss of life.
Therefore, if the rim of the toilet is less than 20cm (8") above the
waterline when the craft is at rest, or if there is ANY possibility that the
rim of the bowl may be below the waterline at ANY time, a ventilated
anti-syphon loop MUST be fitted in any pipework connected to a
through-hull fitting, irrespective of whether inlet or outlet.
USE VENTED LOOPS!
 
<span style="color:white">. </span>
Yes, I read the manual as well. Of course it says that - Jabsco don't want to be sued when someone's boat sinks because the joker valve is knackered.

However, joker valve failure is generally slow and trickly, not catastrophic - and if you have one of the new twist and lock mechanisms the locked piston is a pretty good backup.

The flap valve on the inlet is less reliable though.

Surely if you tell your crew they will die horribly if they forget to close the seacocks that will get their attention?

Anyway, you are right - for most boats a horrible great loop of sanitary hose is probably the best idea. I won't be fitting one though.

- W
 
Had 3 toilets on boats with no syphon break and all at or below the water-line (all on Benes from 1992ish). never had a problem; just made us remember to shut the sea-cocks when not in use. On one the WL was about 5mm below the toilet rim - guess how we found out!!
 
I have ASV's on both pipes now.

Forgetting to close a sea cock is an accident but not having vented loops as instructed is gross negligence and the insurance may well be void.
 
[ QUOTE ]
. . . not having vented loops as instructed is gross negligence

[/ QUOTE ] Oh no it isn't - and I have that on good authority from the Headsmistress.

And - we only have 3rd party insurance, so unless we hit a submarine on the way to the bottom after going 'down by the heads' we should be alright.

Forgetting to close a seacock is gross negligence. Not fitting vented loops is a choice.


- W
 
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