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Old 05-06-2008, 03:02   #1
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Vented Loops in Head Plumbing?

Does anyone NOT have vented loops in the inlet / outlet plumbing of your below waterline toilet?

I am fully aware of the reasons and recommendations for fitting vented loops when the toilet bowl is below the heeled waterline but I am wondering how many people KNOWLY decide not to fit them.

As you might guess, I am CONSIDERING not fitting vented loops and I understand the risks involved; am I only one (perhaps the only idiot - - ?) to consider this.
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Old 05-06-2008, 03:33   #2
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Had a yacht with vented loop in the interior which consistently smelled OFF. Eventually the vent corroded closed - the smell stopped but had an overflowing toilet on one occasion - nothing is maintenance free obviously.
Eventually I decided to install a second stopcock at the toilet which I religiously closed after use. Given there are times when I was too tired to function properly it would be sensible to keep the vent but take it to the exterior.
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Old 05-06-2008, 04:55   #3
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I recommend Vented Loops [1] and Seacocks [2] on ALL plumbing lines (inlet & ouilet) connected to through-hulls; however some recommend the Vented loops NOT be installed on Inlet lines [3].

[1] If the toilet is connected to any through-hull fitting, and if the rim of the bowl ever falls below the waterline, water may flood in (back-siphon), causing the craft to sink.
Therefore, if the rim of the toilet is less than 8” (20 cm) 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 (heeled), a vented loop must be fitted in any
pipework connected to a through-hull fitting, irrespective of whether inlet or outlet.
USE VENTED LOOPS!
Mount the vented loop so it will remain above the waterline at all heel angles (fully loaded). Clean the anti-siphon valve regularly to keep it functioning.

Although moving the flush control lever to the “Dry” (closed) position will restrict the flow, this lever cannot be relied upon as a safety device.
To make a loop in the hose without mounting a vent may be as hazardous as no loop at all, because water will siphon over the loop.
IN FACT, IT IS THE VENT THAT ACTUALLY PREVENTS THE SIPHON.

[2] If the toilet is connected to any through-hull fitting and if the toilet or the pipework are damaged, water may flood in, causing the craft to sink. For this reason, if you are making connections between the toilet and any throughhull fitting that may be possibly situated below the waterline, full bore seacocks must be fitted to such hull-fittings, to allow them to be shut off. The seacocks must also be positioned where they are easily accessible to all users of the toilet.

[3] According to Don Casey, a vented loop in the inlet line can interfere with the proper functioning of the head, and its omission poses less risk because of the positive-action valve on the inlet side of the head. But if you leave the loop out, you must keep the inlet valve in good working order. A screen filter to exclude grass and other debris is highly recommended.
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Old 05-06-2008, 05:45   #4
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We have a simple boat - both the inlet and overboard water seacocks can be reached while sitting on the can. The seacocks are closed unless using the head.

If we had vents they would basically loop over the people sleeping in the v-berth.

If I could not reach the seacocks or they were going to be open for extended periods or while underway I would vent them.
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Old 05-06-2008, 06:05   #5
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We don't have vented loops, and our toilet bowls were installed with the top above the waterline--before we moved aboard and lowered the boat 4 inches.

The net result is we occasionally hear water slopping over the top of the bowl. This has happened when someone forgets to turn the inlet valve to dry, or when the inlet valve failed. It has probably happened on the average of once every year or two. We have also had problems with the joker valve on the outlet, but usually the smell alerts us before the toilet overflows.

When the toilet overflows, the water goes into the shower sump, which will eventually fill up and overflow into the bilge. We have an automatic bilge pump on at all times, with a backup larger automatic pump if the water level rises. The important thing about the toilets is that the the leak is on the order of a gallon or two per hour, while the bilge pump capacity is a couple of gallons per minute, and the backup is about 20 gpm.

Bottom line, for the toilets to sink the boat, we would have to not notice the leak, and both bilge pumps would have to fail...we do close the toilet thru-hulls when we leave the boat for more than a day.
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Old 05-06-2008, 06:17   #6
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I used to own a boat that didn't have a vented loop on the discharge pipe. Simple reason being, it was quite impossible to fit one. Just open and close the seacock as required.
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Old 05-06-2008, 07:15   #7
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I've sailed on many boat without vented loops in either the intake or discharge lines. They say it's less safe but I've often wished that was the way my boat was set up. The maintenance is so much easier. No miles of hose hidden behind bulkheads.
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Old 05-06-2008, 07:20   #8
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yes, indeed

The head in our Cape Dory is below the waterline and the intake hose has no loop. It is NOT a problem for us because the seacock is NEVER open unless the head is being used. The seacock can be reached while sitting on the head, so opening/closing is very easy.
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Old 05-06-2008, 07:28   #9
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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.
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Old 05-06-2008, 07:45   #10
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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.

Vasco:

My wife and I often say it's a good thing there are two of us to remember as we age!! The head seacock is treated like a loaded gun and is constantly being checked to be sure that it is closed. A nice feature of the 25D is that it can be seen from just about everywhere on the boat, including the cockpit!
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Old 06-06-2008, 03:09   #11
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Smile Thanks

Thanks for the feedback everyone.

The use or otherwise of vented loops seems to me to be another of those "risk management" issues that pop up everywhere when owning a boat.

At one end of the spectrum, there a zillion warnings that the non-use of vented loops will sink your boat (usually sooner rather than later). At the other end, it a case of keep your seacocks in good nick and shut and you will be safe.

I suspect the truth lies in the middle and is more dependant one's boat, fittings, hoses, guests and atitudes than the use of the vented loop; however there is no doubt that the use of vented loops IS SAFER than non-use.

For the record, my previous two boats did not have vented loops and neither of them have sunk - yet- for any reason, touch wood. I didn't even know about vented loops on the first one - 25 years back. Second time, I just followed the first system.

Now I know better and have to make an informed decision. Currently I am still leaning towards KISS - no vented loops. The seacocks are in plain view, easy reach from the throne, makes the plumbing much simplier and tidy, far less hose to fail and provides a continious real time test of the seacocks (not sure if that is a real good thing, actually).

At the end of the day, I am a bit anal about shutting seacocks (pun perhaps intended ) so don't see much of a problem - I am also a very pedantic about crew / guests and seacocks.

And from the replies so far, I am not the only one taking this path - again thanks to everyone taking time to reply, it is appreciated.
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Old 06-06-2008, 03:33   #12
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For the record, my previous two boats did not have vented loops and neither of them have sunk - yet- for any reason, touch wood...
...Now I know better...
In my foolish youth, I habitually exceeded the speed limits (often extravagantly so), and didnít wear a safety belt .
I have not yet been killed in a motor accident.
This is less evidence that thereís no need to respect the laws of physics (& man), than it is of my extraordinary good fortune (luck).
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Old 06-06-2008, 03:59   #13
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In my younger days I worked aboard a research vessel in the Gulf of Mexico that almost sunk because someone left the head-valve open on an unvented system. Of course, I was so sea-sick at the time that I was hoping the boat would sink and I'd be dead!
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Old 06-06-2008, 04:09   #14
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I suspect the risk of sink from a bowl rim being below the static water line is slim to none.

For vessels that DO have this condition and DON'T have vented loops they would typically close the sea cocks when the fixture is not in use.

Shiva cam without loops and the seacocks are visible and accessible and so we typically close them when sailing, or when leaving the boat and they remain open when at anchor. The rim is slightly above the static water line so even then sinking is not possible.

For those who have concealed seacocks, with lockers for example, where the are not easily accessible AND a head rim below the static water line it is a wise idea to use a loop.

I installed a loop and I may change back next hose renewal. Never had a problem with no loop, so I was being over cautious.
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Old 06-06-2008, 08:36   #15
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...... than it is of my extraordinary good fortune (luck).
I hope it continues to hold for you
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