Vented Loops in Head Plumbing?

[GordMay]

Originally Posted by Wotname

I hope it continues to hold for you

Like you, "now I know better"

[gonesail]

no vented loop in my head intake but the head is above waterline ...

I think I count three opinions (and some minor variations):

Defjef thinks its a bogeyman and not a big deal (somehow his wishful thinking overwhelms the laws of physics)

Several others rely on their own personal reliabilty in closing seacocks.

Gord gives the "official" party line about what to do and why.

Like all internet discussions you can pick the answer you want.

[btrayfors]

Right...there are always options.

I just installed two vented loops on a boat yesterday. It's really no big deal...easy to do and good insurance.

One loop belongs on the 1.5" waste discharge line, and one on the 3/4" water intake line after the pump (not before the pump, as it could render the pump ineffective).

You do have to keep them clean, but this isn't a big problem.

Even with vented loops installed, it's still good practice IMHO to close seacocks when you leave the boat. For one thing, this "exercises" the seacocks to be sure they'll shut when you really need them to. It also exercises you....kneeling and bending aren't bad things to do :-)

Bill

[drh1965]

I have vented loops on the input and output side but I have found that the pump output is not as strong with the vented loop between the pump and the bowl. I figure that there is a tiny leak in the vented loop that keeps it from sealing 100%. I can never quite get the bowl completely dry. They are cheap marelon vented loops so I'm not completely shocked.

[Ex-Calif]

Originally Posted by Vasco

Randy,

In my mind this is the ideal way to go. This way the seacocks are always closed except when using the head. Of course you have to double check if you've got guests. If you sail with a partner you soon get into the habit of asking each other whether the seacock has been closed or whether something has been switched on or off (such as the propane solenoid or anchor light). I don't know if it's a safety thing or it's just that we're aging and can't remember anything.

We brief people on head use including opening and closing seacocks.

We also use a "shut down" checklist that includes electrics, seacocks, mooring line, cockpit items etc.

When we have more than one person on board the list is divided - Bow = morrings - Cockpit = tiller tie off, secure lifelines, bige pump set, sheets secured etc. - Cabin = electrics, seacocks etc.

We aren't crazy anal about it but we usually get the job done.

[Wotname]

Originally Posted by btrayfors

....I just installed two vented loops on a boat yesterday. It's really no big deal...easy to do and good insurance. ....l

Of course I will use vented loops, I just never knew it until this morning.

Enlightment came as I was opened another 6 litre pack of epoxy. I was considering the cost of the epoxy and all the other bits and bobs of this project (say $30K to date)- my rationale is always to use the best I can afford (not neccessarily the best ).

Vented loops as Bill rightly points out "is really no big deal" and as I KNOW it's safer, vented loops it will be.

Thanks everyone for helping me to "know this".

[MidLandOne]

Originally Posted by btrayfors

...and one on the 3/4" water intake line after the pump (not before the pump, as it could render the pump ineffective).

They can go before the pump if you know the secret method and doing so sure cuts down on the pipework involved and much tidier if the loop is wanted to be hidden away somewhere.

Ours is before the pump (on a manual Jabsco head) with no problem using a very slight mod to a Forespar siphon breaker.

[btrayfors]

You wanna share that mod with us, or just keep us guessing? :-)

Bill

[MidLandOne]

Originally Posted by btrayfors

You wanna share that mod with us, or just keep us guessing? :-)

Well, normally no one believes me Bill, but here goes .

Using the Forespar siphon breaker as an example - one takes the little ducks bill rubber valve out of it and replace with a cube of open cell foam just large enough so that it just squishes nicely into the round fitting the duck bill was in, then screw the top back on. Foam such as a bit cut off the narrow strips one can get for sealing domestic windows, etc serves fine, just has to be porous.

So, when one pumps the amount of air that can get in through the pores of the foam is very small and nowhere near enough to affect the pumping at all. When one stops pumping there is though, enough leakage to allow the siphon to drain down (I have double, double checked that bit ).

I have to say I was a bit sceptical when the builder did this but has lasted 12 years with the same piece of foam and no problem at all. Because the foam is normally under suction on the water side when there is water in the loop I found that it didn't even need washing periodically to get salt out of it.

So, for the likes of a Jabsco one just keeps the short piece of white hose that runs from the pump to the bowl as is. The loop can be between the seacock and the suction side of the pump away in a locker somewhere and no need for the two runs of hose otherwise needed from the toilet to it.

Very obviously, this does not work (nor needed) on the pressure side of a pump else very unhappy experience will result .

While I say above to do the mod on the air valve fitting itself (and that works fine), as these can dribble a little water from time to time (the duckbill on a pressure side of a pump is much more prone to this than foam on the suction side though), if desirable I extend these using hose and ss fittings to somewhere where any leakage does no harm - in the case of Forespar the fittings are 1/4 inch and one can screw the air valve fitting onto the threaded side of a male 1/4" hosetail, then hose back to a hosetail in a 1/4" F/F bend or socket on the thread the valve normally fits onto the loop fitting.

John

[Wotname]

Originally Posted by MidLandOne

Well, normally no one believes me Bill, but here goes ....

Woohoo Mid, I think I might take a chance and believe you on this one, especially as I am fitting a Jabsco manual at the moment. Putting the siphon break after the pump was looking untidy so this might be the answer. Anyway, it's a mono so you probably know something about them .

Thanks for sharing the hint.

[Lancerbye]

All these problems disappear with a Vacu Flush Head.

[MidLandOne]

Originally Posted by Wotname

Anyway, it's a mono so you probably know something about them .

Actually we've got a cat that suffers from toilet plumbing problems so pretty expert on those too. It gets Feline Lower Urinary Tract Disease if we are not careful with its diet.

Whoops, getting confused here, wrong sort of cat - silly me .

John

[Wotname]

What's a cat? Are they a NZ thing (like a K1W1), can you get more than one type? Can they be put down the head - Oh heck, I had better stop right now - sorry if I have offended anyone!

[MidLandOne]

Well Wot our cats are pretty similar to this Australian one that I photographed a while ago, except ours have tails.

Was very impressed at how well the plumbing is hidden away in this one - don't think it has an antisiphon loop tho', just plumbed straight to the seacock I imagine.

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