why is my vented loop leaking more and more

[Searles]

If the leaky syphon beak in in the salt water discharge side of the exhaust system,check exhaust back pressure ,the leaky unit may indicate an increase of exhaust back pressure .

[sinnerman]

They sell a repair kit to replace the vent. Or just buy a new Anti-siphon loop if the kit is not available for your boat.

You can also remove the vent valve and plumb a hose to it running overboard as one person mentioned.

[Icarus]

Originally Posted by phorvati

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.

Just unscrew the green anty syphon valve and clean it..most likely some dirt stuck in it...

[Pandor]

As some have posted, if water is leaking from the vent line, at least you know the check valve is not stuck shut which would defeat the purpose of the anti-siphon.

But I might also mention that the OP stated he has run the run-off tube from the vent straight up in an effort to mitigate the dripping. This also defeats the ability for the valve to vent and break the siphon.

Any tube coming off the vent should be run downhill (usually towards the bilge) so the water drips can drain and air can enter the vent. Also make sure it doesn’t terminate so low in the bilge that the end could be under bilge water.

[phorvati]

Originally Posted by Searles

If the leaky syphon beak in in the salt water discharge side of the exhaust system,check exhaust back pressure ,the leaky unit may indicate an increase of exhaust back pressure .

I have replaced the anticipation loop with a new bronze from Groco(https://www.groco.net/pvl-2000). And the new one is leaking as well. Vlave is clean.
My raw water is 1" ID hose and goes from pump, to oil cooler, then heat exchanger then transmission cooler, then 6' hose up high to anti-siphon then back down to exhaust elbow. I have replaced the raw water pump as part of regular maintenance.
I think if exhaust back pressure is too high, would it still explain this valve leaking? I have drained the muffler and inspected the hoses coming from elbow and into the muffler, that's 6" section of 3" ID hose. after the muffler exhaust hose is 2.5" ID and its about 20 feet long, no 90 deg turns, and goes to stainless water lift up high in lazarette. after that its straight down to near waterline exhaust port. No flapper valve.

Perhaps take a peak into that 20' section of exhaust hose or waterlift.

[Searles]

Back pressure in a marine exhaust system ,can cause early engine failure ,loss or lack of power ,the best overall guide to the systems is the one provided by Vetus marine systems ,this a simple easily understood diagram by diagram explainable on just about any vsl power or sail .⚓️👍

[phorvati]

So looks like I only get leaks at startup. Once engine is warmed up, leak goes away. So check valve of the vented loop is before the elbow so its not really in the exhaust. There is no way for fumes to go up 1" hose and cause fumes issues in the cabin that way.
But i wonder with cold engine, is raw water seeing higher resistance at the mixing elbow so that water pressure penetrates the vented loop diaphragm?

I motored about 10 hours this passed weekend. I left the hose in the hanging locker where the vented loop is, I just ran it up to the ceiling as high as it would go and back down to a bucket at the bottom of hanging locker. Prior to this, hose went through the floor of hanging locker and was dripping into the engine compartment / bilge.

What I noticed is that at startup or idle while warming the engine or raising the anchor, small 1 Gal bucket got about half full. I emptied it while motoring. But then after 5h of motoring at cruising RPM, I barely got any water into it. This is possible as I never knew how much water was really leaking. I would notice wetness in the engine compartment below the hanging locker floor, and water dripping during my initial engine check at startup. So i was assuming its leaking all the time. But i guess not.

[pcmm]

One thing you haven't mentioned yet is WHERE the vent is leaking from? and where the new vent is leaking?

For me the best and most trouble freen "vented loops" are the ones with no valve in them and a hose attached that leads to a throughhull. I have the vetus version and there is no valve, just a 1/4" ID hose that leads to an overhoad through hull. When the engine is running there is a small stream of water running, just a trickle at idle. I have a center cockpit so seeing this tell tale of water tells me that the raw water pump is functioning as it should and if/when the strainer starts to plug with weeds this stream disappears before the engine raises temp at all. great feature. but back to the issue. Where is the vented loop leaking from?

[phorvati]

i have a diaphragm and I believe a 1/4" ID diameter hose. And the hose is leaking. It is note feasible for me to route this overboard as i would have to drill through finished cabinetry and teak interior. This in in the center of the boat above engine room.
I routed the hose up about another 3-4 feet above the vented loop. I have a new grocco anticiphon valve in place of the one shown. Same as shown, just new. Hose used to go down into the bilgde, but now it goes to the bucket.(top of the bucket) I have about 6 inches before hose gets submerged by water in the bucket. So by no means a permanent solution. It was a setup to observe whats happening.

[noelex 77]

Originally Posted by phorvati

It is note feasible for me to route this overboard as i would have to drill through finished cabinetry and teak interior. This in in the center of the boat above engine room. .

This is a pity. What about a discharge into one of the cockpit drains?

For others reading this thread if you can remove the valve and replace this with a direct overboard discharge you will achieve a couple of important advantages:

1. It will not leak
2. There is no valve to block closed and cause extensive engine damage.

[phorvati]

Originally Posted by noelex 77

This is a pity. What about a discharge into one of the cockpit drains?

For others reading this thread if you can remove the valve and replace this with a direct overboard discharge you will achieve a couple of important advantages:

1. It will not leak
2. There is no valve to block closed and cause extensive engine damage.

Some would argue that Grocco instructions state that valve should be cleaned and it should not leak, and it does not need a hose routed overboard. Also running long hose could kink or clog with debris jeopardizing flooding the engine.

[Bowdrie]

Originally Posted by phorvati

after the muffler exhaust hose is 2.5" ID and its about 20 feet long, no 90 deg turns, and goes to stainless water lift up high in lazarette. after that its straight down to near waterline exhaust port.

Are you saying that there are two water lift mufflers?

[phorvati]

6" from elbow there is a muffler. 3"ID input and 2.5"ID outlet. Then 20 feet later at the stern in lazarette, there is a waterlift Custom made stainless steel. It goes up high above the waterline and then straight down to outlet port near waterline. I am not sure if waterlift is a muffler. This pic summarizes my setup accept I have a stainless waterlift instead of loop.
https://www.abcpm.co.uk/images/vetus...s/exhaust1.gif

[Bowdrie]

Originally Posted by phorvati

6" from elbow there is a muffler. 3"ID input and 2.5"ID outlet. Then 20 feet later at the stern in lazarette, there is a waterlift Custom made stainless steel. It goes up high above the waterline and then straight down to outlet port near waterline. I am not sure if waterlift is a muffler. This pic summarizes my setup accept I have a stainless waterlift instead of loop.
https://www.abcpm.co.uk/images/vetus...s/exhaust1.gif

We're still in riddles.
In your first sentence there is a "muffler", we assume that is a "water lift" muffler right after the engine.
Then in 2nd. sentence after 20' of run there is custom stainless "water lift".
In the 3rd. sentence you're not sure if "water lift" is a muffler.
And in last sentence you have stainless "water lift" instead of a "loop"

I reckon that "muffler" or "water lift" at the stern is neither of those, but simply a "loop" that prevents a following sea from flooding that 20' of run?

Anyway, it seems that the exhaust from the engine has to push a lot of water over both a lot of height and a lot of length, that does create back pressure.