Piddle tubes

[zoidberg]

I've installed an anti-siphon loop of heater hose between the heat exchanger and the steel exhaust elbow, which will carry exhaust water to be mixed with hot gas prior to entry to the Vetus plastic mixer bottle. As recommended, this loop comes up to the underside of the bridgedeck.

It is suggested that a Vetus siphon-break device be fitted at the top of this loop, which others suggest is an 'extra belt' to a belt-and-braces approach. Yet others suggest fitting a 'piddle tube' instead, which is a small bore tube inserted into the heater hose at the high point, and led out to a point above a cockpit drain, where the small-but-continuous dribble of water will be visible from the helm.

Should that stop while motoring, it would indicate a failure in the supply of cooling water perhaps just ahead of an engine overheat alarm.

I'm aware others have commented on this idea, but a Search fails to turn up much that's helpful. Would anyone with experience of this care to comment?

 

[Tranona]

There are two types of antisyphon valves. The first and most common is an actual valve which breaks the syphon when the water flow ceases - that is when the engine stops. The second type does not have the valve but a take off for a tube which discharges overboard or in some cases into the cockpit and thence out of the drain.

Either work but some people prefer seeing the physical flow from a tube. However it is not always convenient to run a tube out of the engine compartment. Personally I prefer the valve type as I have had no problems with them in 3 boats over 20 years. Just clean the little flap from time to time to make sure it is not sticking.

 

[macd]

...the small-but-continuous dribble of water will be visible from the helm.

Should that stop while motoring, it would indicate a failure in the supply of cooling water perhaps just ahead of an engine overheat alarm.

With ours (the non-valved Vetus unit described by Tranona), it would probably indicate that the engine's only ticking over. If it isn't and there's still no piddle, check for something worse.

I've had the valve-type on another boat, and prefer the tell-tale piddle. The valved type also needs cleaning periodically, as was mentioned: it can be disabled by salt build-up.

 

[BabaYaga]

The second type does not have the valve but a take off for a tube which discharges overboard or in some cases into the cockpit and thence out of the drain.

To complete (?) the picture, there is also the variety that takes the tube to a hose fitting on top of the exhaust water trap.
A good solution in my view, for anyone who would find a dribble in the cockpit a bit annoying: No valve to clog up, no skin fitting needed for overboard discharge.

 

[rogerthebodger]

Discussion currently going on here

http://www.ybw.com/forums/showthread.php?492587-Engine-inlet-anti-syphon

 

[Spirit (of Glenans)]

When I saw the title of this thread I thought for a few seconds that someone was contemplating fitting a facility similar to the "Pilot's Relief Tube" fitted to the DH Mosquito.
(Said tubes were boycotted by the women involved in factory refurbishment of the planes when they discovered what they were for )

 

[Dan Tribe]

When I saw the title of this thread I thought for a few seconds that someone was contemplating fitting a facility similar to the "Pilot's Relief Tube" fitted to the DH Mosquito.��
(Said tubes were boycotted by the women involved in factory refurbishment of the planes when they discovered what they were for ��)

I used to crew on a boat where the skipper used a length of 32mm waste pipe to avoid going on deck to pee. A young disrespectful crew members brought a length of 68mm rainwater pipe, saying "I like your idea Alan, but this is more my size"

 

[alahol2]

I've installed an anti-siphon loop of heater hose between the heat exchanger and the steel exhaust elbow,.... As recommended, this loop comes up to the underside of the bridgedeck.

It is suggested that a Vetus siphon-break device be fitted at the top of this loop, which others suggest is an 'extra belt' to a belt-and-braces approach.

Just to clarify, the 'Vetus syphon break device' isn't an 'extra belt'. Without the valve/piddle device you have not got a syphon break, you have just got a loop of pipe which could well syphon water.

 

[Poecheng]

Our arrangement is that the exhaust discharges underneath the transom (and therefore almost pointing downwards) rather than through the transom. It is not at all easy to see the water discharging.
We have a piddle pipe discharging high up on the port side of the hull at the point of the cockpit; when the engine is given revs above idle, it is easy to see that the water is flowing.
The other useful aspect of this feature is particular to the engine which in extreme circs can set off the high temperature alarm. If you know - when the alarm goes off - that the water is flowing through (because you can see the piddle tube) you know you can carry on for a distance as you haven't got a blockage.

 

[Heckler]

I've installed an anti-siphon loop of heater hose between the heat exchanger and the steel exhaust elbow, which will carry exhaust water to be mixed with hot gas prior to entry to the Vetus plastic mixer bottle. As recommended, this loop comes up to the underside of the bridgedeck.

It is suggested that a Vetus siphon-break device be fitted at the top of this loop, which others suggest is an 'extra belt' to a belt-and-braces approach. Yet others suggest fitting a 'piddle tube' instead, which is a small bore tube inserted into the heater hose at the high point, and led out to a point above a cockpit drain, where the small-but-continuous dribble of water will be visible from the helm.

Should that stop while motoring, it would indicate a failure in the supply of cooling water perhaps just ahead of an engine overheat alarm.

I'm aware others have commented on this idea, but a Search fails to turn up much that's helpful. Would anyone with experience of this care to comment?

on both my beneteaus the discharge from the raw water pump goes to a vetus flap valve device situated above the water line behind the companion way steps. There is a piddle tube from that to the engine tray. From the valve the raw water goes to the heat exchanger and from there direct to the exhaust. I have cleaned the flap valve once but have never seen it leak via the piddle tube.
Stu

 

[VicS]

on both my beneteaus the discharge from the raw water pump goes to a vetus flap valve device situated above the water line behind the companion way steps. There is a piddle tube from that to the engine tray. From the valve the raw water goes to the heat exchanger and from there direct to the exhaust. I have cleaned the flap valve once but have never seen it leak via the piddle tube.
Stu

Because the flap valve closes when the engine is running, but opens when the engine is stopped and a slight negative pressure is created under it. This then allows air to be drawn in to break the syphon.

It is not normal ??? to have the piddle tube as well as the flap valve but it will divert any slight water leakage past the valve to somewhere convenient rather that just dribbling back down the hoses .

The type with a piddle tube normally flows continuously either to a cockpit drain or directly overboard. The advantages of this type are that there is no valve to become inoperative, or require any maintenance. A visible water stream confirms that there is no blockage which would result in the syphon not being broken.

 

[BabaYaga]

It is not normal ??? to have the piddle tube as well as the flap valve but it will divert any slight water leakage past the valve to somewhere convenient rather that just dribbling back down the hoses .

It can be a very good idea to take care of any dribble from a flap valve, in my view.
I once had the older Volvo type pictured below, which has no fitting for a tube. Unnoticed, leaking water found its way along a passing cable, through a bulkhead and into the control box for the fridge, which was destroyed. Horrible design, that was.

 

[PetiteFleur]

When I re-engine d a few years back, I used the Vetus valved anti-syphon unit tucked high up behind a bulkhead on the other side to the engine. I discovered that the valve dribbled and did not work well. I dismantled it, removed the valve and converted it to a dribble tube out the transom, using from memory a 1/4" diameter plastic tube ending in a short length of copper tube epoxied into the transom above the waterline. On idling it just dribbles but as soon as you increase revs a distinct jet of water is seen. No trouble since.

 

[Spirit (of Glenans)]

I used to crew on a boat where the skipper used a length of 32mm waste pipe to avoid going on deck to pee. A young disrespectful crew members brought a length of 68mm rainwater pipe, saying "I like your idea Alan, but this is more my size"

Size matters

 

[PuffTheMagicDragon]

Size matters

As the daughter of a taxi-driver in Cairo allegedly told the late King Farouk, whose reputation as a womaniser was legendary, "It's not what you have that counts, it's what you do with it!"

 

[john_morris_uk]

FWIW we have a small bore tube from the anti-siphon loop to a small skin fitting on the starboard side. It pees a continuous dribble of water no matter what the revs.

I took the valve out of the anti-siphon u-bend shortly after we bought the boat twelve years ago.

Its SOP to have a quick look over the rail to see if the water is coming out whenever we start the engine. If there's any sign of overheating, its also the first thing I check.

 

[Iain C]

I have a tell tale tube that exits the stbd topside, roughly around the bridgedeck area and a few inches below the rubbing strake. It's useful to have, even if my exhuast does exit a vertical transom.

HOWEVER...have a think where it will exit/point. There's been plenty times I've managed to soak the dinghy before going ashore, or soak shopping on the pontoon etc!!

 

[claymore]

We have a piddle tube - it saves leaving the cockpit to check the exhaust on the transom. It does however piddle into the bilge so that needed pumping every once in a while. Have relocated it to come out on the port side so I can lean out and see it. Works fine but does leave a dribble mark on the hull which needs a wipe each day! Doh!

 

[Slycat]

I always thought the piddle tubes were those two holes in the cockpit floor for use when its too rough to go over the side and too rough to risk getting sea sick using the heads inside!