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Old 14-06-2018, 07:52   #1
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Vented loop not working.....

I have a vented loop installed in my Jabsco manual head but it does not work, if the pump lever is in the "pump-in" position water continues to dribble into the bowl and would fill it to overflowing if left unattended.

I am sure that it is installed in the correct position (i.e. between the pump and the bowl) and I have removed and cleaned the duck-bill valve, but the problem seems to be that the duck-bill valve will not open. Has anyone else experienced this problem and can you suggest any remedies?
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Old 14-06-2018, 14:53   #2
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Re: Vented loop not working.....

I suspect the problem may be that you didn't mount the loop high enough. It needs to be at least 6-8" above the bowl AT ANY ANGLE OF HEEL, not just when the boat's at rest...and if water continues to trickle into the bowl even when the boat is at rest, it may not even be above the waterline at all. So depending on where the toilet is relative to the waterline and how far your boat can heel, that would put it 2-4 FEET above the bowl. Which means you can't hide it under the vanity, which is where a lot of owners of larger boats put 'em.

The owners manual for your Jabsco manual toilet is here Jabsco Twist 'n' Lock Manual Toilets Instructions It includes a drawing illustrating how far above the bowl the loop needs to be.

If the loop is where it belongs, you may just need to replace the entire air valve...they aren't expensive.

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Old 17-06-2018, 00:58   #3
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Re: Vented loop not working.....

Thanks very much Peggie, but the loop is comfortably above the heeled level of the bowl and it doesn't work even when the boat is upright!

Maybe it is simply that the duck-bill valve is too stiff so therefore doesn't open properly. I wondered whether there was any clever way of making sure that it doesn't stay closed. I think that first I will try cutting a small vertical slit in it to see if that helps. If not I will find a replacement and try that to see if there is any improvement.
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Old 17-06-2018, 04:10   #4
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Re: Vented loop not working.....

Just remove the duck bill and pump slowly. It should not leak if you take it slow.
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Old 17-06-2018, 06:44   #5
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Re: Vented loop not working.....

I think that first I will try cutting a small vertical slit in it to see if that helps.

If you do that it'll stay open all the time, interfering with the pump's ability to prime. If the problem isn't a vented loop that's installed too low, it has to be a defective duckbill or air valve. Just for fun, try removing the air valve and hold your finger over the hole in the nipple while you flush in the "wet" mode, then remove your finger. If that works, try "massaging" the duckbill to soften it up a bit. If THAT doesn't work, replace it or the entire air valve.

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Old 17-06-2018, 06:47   #6
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Re: Vented loop not working.....

Peg is right. I keep getting Jabsco confused with Raritan. Raritan PH-II puts the anti-siphon after the pump where it should be IMO.
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Old 17-06-2018, 08:09   #7
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Re: Vented loop not working.....

Guys, he said the loop is between the pump and the bowl. It wonít interfere with priming there. That is where Jabsco recommends to put one if needed

Itís odd because duck bill valves usually fail open. Maybe something got on it and cause it to stick closed.

Does the siphon stop when you remove the valve?

Check to see if the hole in the cap is blocked.

Is the fitting blocked between the duck bill and the loop?

Something is keeping air from getting into the loop and breaking the siphon.

New duck bill valves are not expensive.
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Old 17-06-2018, 08:21   #8
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Re: Vented loop not working.....

Guys, he said the loop is between the pump and the bowl. It wonít interfere with priming there.

You're right of course... I shouldn't post before I've had my first cup of coffee in the morning!

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