Exhaust Water Trap. What does it do.

[Lofty]

I recently had a bad scare when water got into one of my cylinders through the exhaust system. After examining the system it all seems to be in good order and I know the problem had been caused by water back flowing when part of the system was carelessly removed.

The one piece I am not sure about is the water trap. Despite numerous searches I cannot find any clear explanation of what it does. Is it just another type of silencer or of does it also prevent water back flowing.

Explanations will be most gratefully received

Lofty

 

[sarabande]

if you look in the Vetus catalog, p58 and onwards , there's lots of background info with some very clear diagrams.

http://viewer.zmags.com/publication/fd2b8fee#/fd2b8fee/58

 

[VicS]

I think the Vetus catalogue says it all.

I'll just emphasise that the water trap must be large enough to hold all the water that remains in the exhaust system when the engine is shut down.

 

[Tranona]

Thats a good point. Vetus have a formula for working out the capacity - can't put my hand on it just at the moment. I did the calculation when I installed my new Nanni and the capacity of the unit I fitted was more than twice the recommended minimum. I think it only becomes a problem when you have very long runs from the trap to the swan neck such as you might do if the engine was mounted in the middle of the saloon with a transom outlet.

 

[Danny Jo]

Thats a good point. Vetus have a formula for working out the capacity - can't put my hand on it just at the moment. I did the calculation when I installed my new Nanni and the capacity of the unit I fitted was more than twice the recommended minimum. I think it only becomes a problem when you have very long runs from the trap to the swan neck such as you might do if the engine was mounted in the middle of the saloon with a transom outlet.

Ah! At last I understand why Danny Jo has two traps in addition to the swan neck. One is in the bilge just aft of the engine, which is mounted in the saloon over the aft end of the keel, and the other is located about half-way along the exhaust run.

 

[Lofty]

Thanks for the help

Thanks a lot Fellas.

The vetus catalog has answered all my questions.

I now know that I have two water locks in the system so I should be quite safe. My problem was that someone had removed part of the system, in front of the water lock, to get at the prop connector and raised the pipe as they did so. This caused the water remaining in the pipe to run into the exhaust manifold.

Thanks again.

Lofty

 

[Tranona]

Are you sure the second one is a water trap and not a muffler? The capacity is a function of the length and diameter of the exhaust hose. The standard size for up to 50mm hose has a capacity of about 4.5 litres and the large capacity (for longer runs) is 7.5 litres. For 60-90mm hoses the two sizes are 10 and 16 litres.

Have a look in the Vetus catalogue for details of traps and mufflers.