vented loops in toilet pipes

[andyball]

While repairing the heads on a friends boat (nauticat 44)....noted that 'tho the installation is below the waterline, no vented loops/anti-siphon valves are fitted, just a loop well above the waterline.

Jabsco's instructions are clear: you must have an anti-siphon valve in both inlet & outlet if below waterline.

Everyone I ask in person says there's no need-just make sure there's a loop above the w/l.

I can see that in the event of a major problem with the toilet pump/valves, AND the seacocks being left open....(most likely,knowing the boat/owner) the valves might be necessary.

Anyone got an opinion?...are the vented loops o.t.t. in this case, as local "experts" claim?, or vital equipment?.

Concerns are 1: finding room to fit the b.things, & 2: will the one on the outlet not clog up (thus not doing it's job), or smell somewhat?.

TVM for all advice

 

[ccscott49]

I have loops, but no antisyphon holes/valves, I've never had a problem. Is that any help?

 

[Trevor_swfyc]

Andy.
The manufacture does not want any claim for a boat sinking due to syphon back hence the recommendation. Clearly fitting a system against the recommendation would negate any claim against the manufacturer.
Having said this in reality most yacht owners I am sure do not have a syphon break but have a loop which is well above the waterline when the boat is level. When at sea the danger is that this loop may dip below the water level so anything over force 3 I shut the toilet valves. Also ALL valves must be shut when you leave the boat anti-syphon fitted or not.
PS Use low odour white pipe for toilet outlet, well worth the small extra cost.
All the best.
Trevor

 

[vyv_cox]

I have never owned a boat with the toilet below the water line, although all could have been with the boat heeling on the appropriate tack. None had any form of loop in the suction side, all had a non-vented loop to above the possible water line in the discharge side.

However, thinking about it suggests that this is completely the wrong way around. For water to siphon back through the discharge pipework requires the joker valve to have failed. This must be almost the reliable piece of equipment on the boat - did you ever see a failed one? I didn't. If it did fail the toilet would not pump out too well, so it would reveal its failure quite quickly.

On the other hand, water can flow through the inlet valves without hindrance, as the valves close to prevent it from running back. So there is benefit in having an anti-syphon loop and maybe a break in the suction side, or in closing the valve when not in use. I must say that I never do this but I have known the water level in the toilet to increase after a period of heeling.

 

[Mirelle]

I have the usual loop under the deckhead, no syphon break, never had one, never had a problem. This is with Baby Blakes, which do not have a joker valve on the discharge side - they have a weighted flap at the lower end of the pump and a ball valve in the piston. The Baby Blake will leak through the inlet side, under extreme provocation, unless the top gate valve is screwed down.

I do follow the advice given years ago by Don Street - after flushing, keep pumping so that you pump air up the discharge pipe to break any siphon. This seems a sensible precaution.

 

[andyball]

Thanks everyone....very useful.

I'll likely scrap the vented loops, ensuring as high a loop above the w/l as possible...& encourage the owner to use the seacocks more often,esp. under sail/in bad weather.

 

[snowleopard]

always wondered...

how you fit a vented loop to the inlet. as there needs to be suction in the pipe to pull the water in, a vent would break the suction and you'd be flushing with air.

how is it done?

 

[Miker]

Re: always wondered...

No idea, but I fitted them on both the inlet and outlet while installing the loops. They both work despite my worrying whether I would be able to pump the s**t that high.
My toilet is below the water level and despite turning the seacocks off, once when heeled over I found the heads awash. On reflection, it could just have been the water in the bowl being sloshed around if it had not been fully flushed through. I have a rule that the seacocks should be turned off when not in use but I do not want to have to rely on my crew always remembering.

 

[Roberto]

Re: always wondered...

put the vented loop after the pump

 

[hove2]

see extract from The Code of Practise below. Read the rest at http://www.bluemoment.com/codeofpractice/5.html
5.8.2 When an opening is for the purpose of an inlet or discharge below the waterline it should be fitted with a seacock, valve or other effective means of closure which is readily accessible in an emergency.

5.8.3 When an opening is for a log or any other sensor which is capable of being withdrawn it should be fitted in an efficient watertight manner and provided with an effective means of closure when such a fitting is removed.

5.8.4 Inlet and discharge pipes form water closets should be looped up within the hull to the underside of deck and shell fittings provided as required by 5.8.2. When the rim of a toilet is either below or less than 300mm above the deepest waterline of the vessel, anti-syphon measures should be provided.

 

[Miker]

Re: always wondered...

Very true. The Jabsco instructions emphasised that.

 

[charles_reed]

The majority of boats I've come across do NOT have a vented loop - I suspect that the main reasons for this are smell and cost.

I regularly, when under way, turn off both discharge and inlet seacocks - not only does this prevent back-siphonage but it ensures they keep working.

I suspect Jabsco are unique in recommending the necessity for a vented loop with their toilet - perhaps it's a design characteristic of the device.

 

[ccscott49]

I have two jabscos and one blakes victory, onboard, none of them have syphon breaks, never had a problem.

 

[spark]

I have just fitted a Lavac and had bought siphon breaks for both inlet and outlet pipes but, on reading the installation instructions (before starting the installation, I'm very proud to say) it seems that only the inlet pipe needs the siphon break. I think the discharge pump stops any siphon effect at the other end.

 

[jcr]

I have a Blakes Lavac which I re-fitted some years ago. I asked for and received an installation leaflet from Blakes, which I followed. It emphasises the need for a loop above the waterline and a need for an antisyphon break. Their suggestion was to make a small hole on the topside of the top of the loop. I used a 1/16 drill
for this. It has not given any trouble, but now and again I check that it is clear. I wonder if, in fact, many others have this small hole without realising it.