Need a better understanding?

[Spottsville]

Can someone tell me what this is and the function it preforms and how to tell if it is not functioning correctly (what symptoms does it exhibit when going bad)?

Thanks!
Norm

 

[O C Diver]

Looks like a vacuum break for the wet exhaust system. Depending on the model, it either vents a steady stream of water out the side of the hull when running or not. When you shut the engine off, it opens the loop (highest point in your raw water cooling system) to keep the lift muffler from filling up with water.

Ted

 

[O C Diver]

Where does the vent hose go and does water come out of it when the engine is running?

Ted

 

[Spottsville]

The through hull goes out the side of the hull beside the engine exhaust outlet and does not emit anything I have ever seen when running or not. If is fails will it emit water? Do they need periodic service?

 

[Comodave]

It could be a bilge pump discharge hose. You wouldn't see anything out the through hull unless the pump was running. It does look like a siphon break.

 

[healhustler]

Hey Norm: Why not drop a PM to Kraftee here on the forum. It surely is a syphon break but he would recognize which one.

 

[Spottsville]

Hey Norm: Why not drop a PM to Kraftee here on the forum. It surely is a syphon break but he would recognize which one.

Which one that's really what I'm looking for, then I can get an manual. The PO had a couple of spares onboard but they don't have the valve on them. And are a different size..

Thanks for the suggestion!
Norm

 

[SoWhat]

It's a syphon break valve. It will break the cooling system vacuum when the engine is shut off so you you won't suck water from exhaust or seacock into engine.

Syphon break valve

 

[O C Diver]

Is the device before or after the pump? If before the pump, the line is under vacuum and a plug is sucked against a hole to allow water to be pulled to the pump. If after the pump, the line is under pressure and the plug is pushed against the hole. When the pump stops, the vacuum or pressure goes away, the plug unblocks the hole, and the siphon is broken. Maintenance generally consists of making sure the plug can move freely from one position to the other and that the seating surfaces are in good condition.

Ted

 

[Spottsville]

Is the device before or after the pump? If before the pump, the line is under vacuum and a plug is sucked against a hole to allow water to be pulled to the pump. If after the pump, the line is under pressure and the plug is pushed against the hole. When the pump stops, the vacuum or pressure goes away, the plug unblocks the hole, and the siphon is broken. Maintenance generally consists of making sure the plug can move freely from one position to the other and that the seating surfaces are in good condition.



Ted

This helps a lot. When I read your operational description and look at the picture of the siphon brake in the link posted by SoWhat it makes total sense now.

THANKS!
Norm

 

[O C Diver]

This helps a lot. When I read your operational description and look at the picture of the siphon brake in the link posted by SoWhat it makes total sense now.

THANKS!
Norm

I'm one of those people who has to understand how things work and why they're needed. Hard to know if something isn't working, what the problem might be, if you have no idea what it does and how it does it.

Ted

 

[RT Firefly]

Greetings,
Mr. OC. "Hard to know if something isn't working, what the problem might be, if you have no idea what it does and how it does it."
I guess this would NOT be an appropriate time to make a comment about women would it?

 

[HeadMistress]

That gadget in the top of loop appears to be an air valve, which would eliminate the vent for a vent line on the loop because it stays closed to prevent water that's be PUSHED through a line from being squirted out the vent, only opens to allow air into the line through which water is being PULLED--iow break a siphon. Air valves do require a little periodic maintenance remove any mineral deposit buildup (and/or when installed in sanitation system plumbing, waste material).

That doesn't mean there isn't a vent line on this one, only that when installed and maintained, no vent line should be needed.

 

[TG]

Siphon Break otherwise known as a Vented Loop. The hose coming out the top is the vent line. There should be a one way check valve in the top of the loop.

 

[psneeld]

Not necessarily.

If there is a valve in the loop, then the overboard vent line isn't required.

But on many engine exhaust vented loops, the valve is omitted, thus eliminating one possible failure. A small hole into tubing leads overboard or back into the exhaust system where a siphon could not occur.

Mine was recommended and ordered with the overboard vent line, no valve.

But in this case, there definitely looks like some sort of valve on the loop.

 

[O C Diver]

That gadget in the top of loop appears to be an air valve, which would eliminate the vent for a vent line on the loop because it stays closed to prevent water that's be PUSHED through a line from being squirted out the vent, only opens to allow air into the line through which water is being PULLED--iow break a siphon.

Actually it can be a pressure line. If you don't vent the line to the outside, it may pump water in the boat if the valve sticks open. If it were my boat, that would be a tee with maybe a 1/4" hose pissing a stream out the side when the engine is running. No valve to go bad and a tell tail showing the water pump was working. Obviously the above wouldn't work if the siphon break was on the vacuum side of the pump.

Ted

 

[The Other Gary]

It is nice that yours is out in plain sight. On my boat it was fixed between the inner and outer transom area. I only found it when I cut an inspection plate hole so I could access that area to put in a backing plate for my dinghy davits. Now I check the duckbill annually. Thankfully it worked fine in the 15 years it was hidden away.

 

[TG]

Found This

 

[The Other Gary]

Just as a source of useless information they are also used in urinals to prevent backflow into the potable water supply. It would be a real pisser if the urinal model was cheaper than the "Marine" copy.

 

[psneeld]

Actually it can be a pressure line. If you don't vent the line to the outside, it may pump water in the boat if the valve sticks open. If it were my boat, that would be a tee with maybe a 1/4" hose pissing a stream out the side when the engine is running. No valve to go bad and a tell tail showing the water pump was working. Obviously the above wouldn't work if the siphon break was on the vacuum sise of the pump.

Ted

Exactly what I have....and for the failure reason you state.

Bad news in addition to the brown ICW moustache., I now have a skid mark too.

 

[O C Diver]

Bad news in addition to the brown ICW moustache., I now have a skid mark too.

Try using Tide laundry detergent next time you're at the laundromat.

Ted

 

[Ski in NC]

Figure out what hoses are attached to the vented loop. Could be engine, bilge pump, head system.

If engine, it should piddle out the overboard vent line. It may have a valve in the thingy on the top, if so, service it. A drilled orifice is better than a valve as if the valve sticks, you may not know it until engine is filled with water. With the orifice if you see piddle, you are good to go.

 

[Spottsville]

This is what's in the valve at the top. For all that questioned, its on a raw water hose that comes from the engine and feeds the exhaust elbow before the water exits the engine through the wet exhaust. The picture shows how simple it is. It seems to me if it fails on the pressure side water will come out the vent line and be seen from the side of the boat. If it sticks and does not break the vacuum then what happens and how would you know a problem exist?

 

[psneeld]

You don't and that is generally why check valves in that particular vented loop application are not recommended ......in my readings...and my common sense factor.

But as I said, I had to live with a dribble now down the side of my boat.

Others have expressed how it is plumbed back into the exhaust system....no dribble.

 

[O C Diver]

Try to calculate the height of the siphon above sea level. To a point, the greater the height, the less the risk.

Ted

 

[sunchaser]

Figure out what hoses are attached to the vented loop. Could be engine, bilge pump, head system.

If engine, it should piddle out the overboard vent line. It may have a valve in the thingy on the top, if so, service it. A drilled orifice is better than a valve as if the valve sticks, you may not know it until engine is filled with water. With the orifice if you see piddle, you are good to go.

+1

On my vessel I have three anti siphon breaks for sewage systems and two for engines. The engines' loop valve, piddling all the time, discharge into top of adjacent water lift mufflers. A vented loop is a standard (most) sail boat exhaust hookup.