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Old 03-12-2023, 07:22   #1
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why is my vented loop leaking more and more

I have it connected to a hose. and lifted as high up as it would go. but it's been getting worse and worse in terms of leaking while engine is running.
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Old 03-12-2023, 07:42   #2
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Re: why is my vented loop leaking more and more

Take the vented loop apart and clean out the spring/seal mechanism. It gets gunked up over time. I don’t recognize that exact model but I assume it’s like a vetus.
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Old 03-12-2023, 09:39   #3
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Re: why is my vented loop leaking more and more

Some can be disassembled and cleaned, others are made to be replaced after 20-30 years.
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Old 03-12-2023, 09:55   #4
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Re: why is my vented loop leaking more and more

Springs and valves are a source of disaster in anti-siphon loops. They can fail in one of two ways. They corrode, or get dirt stuck in them and fail open. Now, unless you have a hose attached, they spray salt water all over your engine room. That’s bad.

Or they corrode or get dirt stuck in them and fail closed. They no longer work as a siphon break, and you flood your engine. That’s really bad.

If directed to a proper drain WHO CARES if it dribbles out water? In fact that’s a feature, not a bug because you can direct that water to a place you can easily see it, confirming normal water flow.

Our boat has a simple hole drilled in the stainless high loop on the water line that connects to a cockpit scupper. No valve, no springs, nothing but an hole. Easy, simple, maintenance free, fool-proof.

Water pisses out when the engine runs, air rushes in when it stops. If you lose cooling water flow the normal sound of dribbling water is replaced with engine exhaust, easily noted from the helm. Anything more complicated adds no value.
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Old 03-12-2023, 10:25   #5
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Re: why is my vented loop leaking more and more

It looks like the green top part might just unscrew for cleaning. But as Harmonie said it's pretty common practice to replace that part with a hose that's run up and overboard. If you can see and hear the flow all the better.
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Old 04-12-2023, 02:48   #6
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Re: why is my vented loop leaking more and more

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Originally Posted by Orion Jim View Post
Some can be disassembled and cleaned, others are made to be replaced after 20-30 years.
Steve DíAntonio* has written a couple [at least] of good articles, on Vented Loops:
Antisiphon Valves https://www.proboat.com/2017/06/antisiphon-valves/

Vented Loop Remote Drains ➥ https://stevedmarineconsulting.com/july-2021-newsletter-vented-loop-remote-drains/

The Many Weaknesses of Raw-Water Check Valves
https://www.proboat.com/2017/04/many...-check-valves/

* More articles, by Steve ➥ https://stevedmarineconsulting.com/b...les/#technical

Manuals for Vented Loops ➥ https://www.marinedieselbasics.com/vented-loop-manuals/
Includes Forespar, Jabsco, Kohler, & Vetus
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Old 04-12-2023, 06:51   #7
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Re: why is my vented loop leaking more and more

I took out the spring. Its just a nipple and hose. But i didn't run the hose overboard. Just looped it. It never leaked but it started more and more while engine is running. I guess I'll have to run it overboard. higher raw water flow? or more and more restrictions building up in raw water downstream of the loop. or I might get a new one. Too much at stake for 100$ part.
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Old 04-12-2023, 09:01   #8
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Re: why is my vented loop leaking more and more

To be clear, you are talking about a discharge loop on the raw water discharge circuit on your engine.

As Harmonie described above, our boat also has one set up to discharge overboard through a small diameter through-hull fitting. [1/4 inch to restrict flow and make the stream more pronounced].

The strength of the stream provides a visual indication of raw water flow in the wet exhaust system. It also serves as the vacuum breaker when the engine is not running.

A small or intermittent stream at idle, increasing in strength as RPMs increase [i.e., raw water pump pumping more volume] is normal for our engine. When the stream diminishes from normal, or goes away while the engine is running, it is a warning of low raw water flow to the engine.

Port it to drain where you can see it [preferable overboard] and carry on.

In case this applies to your boat.

Cheers, Bill

PS: Since this is not a closed circuit water circuit like a water flushing head would have installed on the raw intake and discharge lines, no vented loop with a vacuum breaker is required. This is just an open discharge loop extended above the waterline at all angles of heel.
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Old 04-12-2023, 10:52   #9
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Re: why is my vented loop leaking more and more

I see two vented loops in the photo. The stainless one in the foreground has no hoses attached. The one in the back looks like a Groco and has a vent hose attached that should be led to an overboard drain.
https://www.groco.net/pvl-2000
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Old 04-12-2023, 10:56   #10
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Re: why is my vented loop leaking more and more

The valve on the Groco loop is pretty easy to clean which should reduce the escaping flow.

“ HVL and PVL series vented loops assure clog-free anti-siphon protection for sanitation or engine exhaust systems. The oversized vent valve can easily be removed for inspection or cleaning without tools.”
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Old 04-12-2023, 11:02   #11
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Re: why is my vented loop leaking more and more

If the Groco loop is in an exhaust line it must be vented overboard or it might vent exhaust gases into the boat.
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Old 04-12-2023, 11:10   #12
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Re: why is my vented loop leaking more and more

I'm not sure that I agree with just pushing the water overboard. Groco clearly states in their manual that the flapper must be clean and working properly: https://www.groco.net/media/file/file/h/v/hvl-pvl.pdf

"It is essential, particularly when used in waste systems, that the cap be removed periodically and the inside of the loop inspected for obstructions. Ensure that the flapper is not sticking.
A sticking flapper will not allow the vacuum to be broken and may result is back-filling of the toilet or waste treatment system. Rinse the flapper vigorously with clean water."

This suggests the the vented loop will fail to break a siphon.

Isn't water escaping through that overflow hose a sign of a potential failure in this case?
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Old 04-12-2023, 12:47   #13
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Re: why is my vented loop leaking more and more

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Originally Posted by SV Confianza View Post
I'm not sure that I agree with just pushing the water overboard. Groco clearly states in their manual that the flapper must be clean and working properly: https://www.groco.net/media/file/file/h/v/hvl-pvl.pdf

"It is essential, particularly when used in waste systems, that the cap be removed periodically and the inside of the loop inspected for obstructions. Ensure that the flapper is not sticking.
A sticking flapper will not allow the vacuum to be broken and may result is back-filling of the toilet or waste treatment system. Rinse the flapper vigorously with clean water."

This suggests the the vented loop will fail to break a siphon.

Isn't water escaping through that overflow hose a sign of a potential failure in this case?
When used in an engine exhaust the loop should be vented overboard in case the valve fails. If not vented overboard, exhaust fumes can get in the boat. The vent is just a backup in case the vent valve fails. When you see water being vented it means the valve has failed in the open position and should still work as a vacuum breaker. Some people just remove the valve and leave it vented overboard, one less thing to maintain. Of course that wonít work on a suction side vented loop, those need the valve.
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Old 04-12-2023, 12:56   #14
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Re: why is my vented loop leaking more and more

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. Of course that wonít work on a suction side vented loop, those need the valve.
Why, exactly? The valve always lets air in, thatís its job.
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Old 04-12-2023, 13:25   #15
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Re: why is my vented loop leaking more and more

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Why, exactly? The valve always lets air in, thatís its job.
Youíre right! Donít know what I was thinking. Actually a vented loop should never be installed in a suction line. It would prevent suction!
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