Plumbing for Heads - Vented loops - necessary?

[Kevhillyer]

I have a 12 year old yacht which has stainless steel waste tanks which have corroded in the corners. I am about to replace with plastic tanks, and will replace the heads pipes at the same time.

The pipes and seacocks in the heads are probably the original and despite reading all about fitting vented loops to pipework above the heeled waterline I have questions as to whether this is really necessary. I have previously helped in a yacht club and when we took delivery of new bavarias and beneteaus and had to "code" them for charter, I remember the vented loop issue also had to be addressed - seemingly the boat manufacturers do not provide for this.

1) Are these pipes really necessary given that this yacht (and presumably most supplied without vented loops) has been sailing for 12 years without a problem from the pipe arrangement.

2) I am struggling to find a way to unobtrusively fix a vented loop high enough. Is even a small loop better than no loop. I assume it HAS to be vented else it would just syphon - but I am slightly concerned that venting will lead to other potential leaks or smells.

Any views or insight into how others have upgraded their installations would be gratefully received

Thank you

 

[BabaYaga]

I think a lot depends on which routines you follow.
My boat has no vented loops, it has been fine for over 30 years.
But I make sure that the toilet outlet seacock (ball valve) is closed after EVERY use and the same goes for the valve in the inlet pipe. On leaving the boat, ALL seacocks get closed, except for the cockpit drains.
Some people seem to leave their seacocks open most of the time. They need vented loops IMHO.

 

[Tranona]

And vent should not be necessary if all your waste goes through the holding tank as that will be vented to atmosphere. If you do have a direct overboard bypassing the tank a vent loop may be necessary if you experience any syphoning back through the waste outlet. Guess if you have not experienced it in 12 years it is not an issue.

 

[VicS]

What BY says is basically it.

Vented loops on the inlet and discharge pipe work or shut the sea cocks every time. If toilet not above heeled water line

Loops must go above the heeled water line. Vents allow air to enter, not escape, so should not cause smells.

Joker valve on a direct to sea discharge will limit an inflow but without a vented loop on the inlet nothing ( apart from the secock) to stop an inflow.

Arrangements with holding tanks will depend on the set up


essential on chartered boats I guess 'cos youd not be able to rely on people closing the seacocks every time Esp children ... Infact i know of someone whose boat nearly sank overnight with the whole family on board because one of the chidren had left a seacock open. Water up to the level of the bunks by the early hours.

luckily club rally so lots of help to wash and dry everything at local campsite laundry

 

[Kevhillyer]

Thanks for the replies, all helpful

It is true that there has been no problem so far. I always close seacocks when leaving but generally leave them open whilst sailing.

Presumably for the inlet water to syphon into the boat, there would need to be a defect in the heads which somehow meant the water kept filling ?

I had not considered how the vent in the holding tank would help - I am thinking of keeping one holding tank for one of the heads, but the other I plan to make a direct discharge only - and replace the waste tank with an additional fresh water tank instead.

Appreciate the advice

Kevin

 

[garvellachs]

Vented loops are just another safety thing. The odds are that they will not be needed on any individual boat, nor will the carbon monoxide alarm, the fire blanket, the epirb, the dsc mayday button, etc etc. And the odds are that I will never need my airbags on the car, nor even my seatbelt I suppose. But on the other hand, across all boats (and cars) such safety measures save damage, injury and even lives every year?

A sea toilet mounted below the waterline, joined to underwater thru-hulls with open sea-cocks, relies on the valves in the toilet to keep sea water from flowing in. Unfortunately valves in sea toilets are affected by paper and waste and deposits that affect their efficiency sooner or later. Hence the safety measure.

 

[prv]

A sea toilet mounted below the waterline, joined to underwater thru-hulls with open sea-cocks, relies on the valves in the toilet to keep sea water from flowing in.

There's a couple of valves which will do that on the outlet, though I wouldn't want to rely on them. But on the inlet of the typical Jabsco, there is no valve holding the sea out. Both valves open in the inwards direction, and indeed if you leave the lever in the "dry" position (as many people mistakenly do) then you disable one of the valves leaving just the other.

Pete

 

[KellysEye]

The previous owner hadn't fitted a vented loop nor did I and never had a problem by turning off the inlet after flushing.

 

[prv]

The previous owner hadn't fitted a vented loop nor did I and never had a problem by turning off the inlet after flushing.

Sure - but a system where you can flood the boat by forgetting to do something (or having someone else on board who doesn't know or forgets) is a defective system in my book, even if you can work around it. Wherever feasible, systems should always be designed to fail safe, and "simply remember to close the seacock after every use" does not fulfil that. For the price of a couple of metres of hose and a twenty quid plastic fitting you can eliminate the possibility completely. It seems crazy to me not to.

Pete

 

[affinite]

The vented loop on the outlet does significantly increase the effort and number of pumps required to empty the bog. ie pumping everything uphill for an extra metre
I do have V.loops on both heads but sometimes (after the 20th pump) wonder about removing them and locking the diverter valves in the holding tank position
My brothers boat (Sadler 32) has no holding tanks and no vented loops and his pump out is a doddle by comparison

 

[Niffler]

Perfectly possible for the little plastic duck valve in a vented loop to fail - be honest, how often do you test yours? If you don't test it daily then each night you're trusting your boat to a little plastic valve you might have fitted five years ago and is now blocked. Just like I trust the two outlet and one inlet valves on my loo, together with a very small regular loop - no vent - that means that water would have to really try hard to get there unaided. I know because I can take the pipe off the loo with the seacock open and nothing comes out. I hate the ugly mess of snakes festooned around some people's loos.

 

[laika]

Vented loops on the inlet and discharge pipe work or shut the sea cocks every time. If toilet not above heeled water line

I suspect that by "inlet" VicS means the pipe between the pump and the bowl. You *don't* want a loop on the inlet pipe from the seacock to the pump.

Replacing thousands of pounds worth of vacuflush kit with a couple of manual twist-n-locks was my first task when I bought my current boat and me being me I researched and observed a lot. AWBs never have vented loops although it's not always easy to judge the waterline from inside at a boat show. Nauticats and Najads *always* have correct vented loops on the outlet and between pump and bowl. Obviously when you go big and high-end it's all electric.

I asked a guy from Jabsco (who seemed particularly clued up) whether the vented loop thing was just @r$£ covering or if it was really worth doing. He assured me he wouldn't NOT fit them to his boat. But as the OP points out, plenty of boats don't have them.

FWIW the 19mm vented loops (for the lop between pump and bowl) will sit neatly within the arc of the 38mm vented loops for the outlet so you can mount them on the same vertical surface one within the other. I did fit them, even though it required drilling additional holes for the pump to bowl loop: Westerly's original toilets obviously did't use them.

 

[Niffler]

I suspect that by "inlet" VicS means the pipe between the pump and the bowl. You *don't* want a loop on the inlet pipe from the seacock to the pump.

Westerly's original toilets obviously did't use them.

Just about every installation of vented loops that I've seen has the vent on the wrong inlet pipe - the one from the seacock, though I did see a picture of a loo with vents on all three pipes - the most awful mess imaginable.

As for Westerley's not having them, they are in the majority, most new builds have never had them. It's a funny thing to trust, a little plastic valve you can't see and never test, but perversely you'd not trust the valves in the toilet, which whilst you also can't see them, you test every time you use the loo. A vented loop will fail unsafe, but failure of the valves in the loo is immediately apparent.

 

[nigelmercier]

My boat has loops, but only one is vented. The only reason I did this was to tidy up a loop.

 

[prv]

Perfectly possible for the little plastic duck valve in a vented loop to fail - be honest, how often do you test yours?

I can hear mine hiss as the air rushes in and the water drops back down the hose, a couple of seconds after I stop pumping.

Pete

 

[prv]

I hate the ugly mess of snakes festooned around some people's loos.

Indeed, and quite bad for trapping "spills" and causing smells too. With a bit of thought this can usually be avoided, either by boxing them in or taking them through an existing partition. My loops are in the corner of the cockpit locker, there's hardly any hose visible in the heads compartment.

Pete

 

[Niffler]

I can hear mine hiss as the air rushes in and the water drops back down the hose, a couple of seconds after I stop pumping.

Pete

We're talking about the vented loops right? Otherwise that could be way too much detail about your visit to the loo.

 

[Kevhillyer]

Again, thank you all for your contributions. As with so many things, I am learning that there are other aspects to consider rather than a simple yes/no answer....but it certainly helps to make a more informed choice.

Decisions, decisions !