Standpipe Construction

[Administrator]

For those of you with standpipes in their exhaust systems, what material was used to make them?

Bill

[ArtJ]

Bill

I have a Tartan 34 Classic. All originally have a standpipe.
The standpipe is made of bronze. Lead up to by black pipe which
is threaded into the bottom of the cylinder.

Art

[joe_db]

Black Iron.
Home Depot special

??? - Is the standpipe the same thing as the riser?
If not, then I don't have one.

[hanleyclifford]

Good question. I would say that a standpipe is indeed a riser that elevates the exhaust to such a level that the engine does not have to drive water uphill. So a standpipe is always a riser, but a riser is not a standpipe.

[ArtJ]

Could someone please explain in greater detail the diagram of risers and
standpipes? I think I have a standpipe, especially since the engine is
buried in the keel on the Tartan 34C. The water must push uphill though.

Thanks

Art

[ndutton]

Art,
Is the question how the standpipe system works or whether or not you have one? Or both?

[ArtJ]

Neil

I believe that I have one, but don't understand how a riser differs and
why according to Hanley's post a standpipe doesn't need to lift water.

There may be some confusion from others, including myself how the 3 systems
work and differ (including water lift.

Regards

Art

[hanleyclifford]

Art - The answer is that the standpipe rises so high that when the water is finally injected it is at such a vertical position in the system that the water simply flows downhill and out the transom. The exhaust is not impeded by the water and there is no "batching". Regards, Hanley

[ndutton]

Yeah Art, understand how it could be confusing.

First, the term 'riser' is used for a variety of things. In our exhaust systems it simply refers to a pipe going up, a component of the system. I used the term over on the 'no more fouled plugs' thread to accurately describe a vertical structural component (bulkheads are perpendicular to the centerline, risers are parallel).

You are correct that the raw water must be lifted to a point higher than the waterline in all marine exhaust systems (except keel pipe/dry stack systems that don't pump raw water aboard and therefore don't have to expel it but we're not going there). In the standpipe system the water is lifted by the raw water pump. The waterlift system uses exhaust pressure to lift the water, hence the name. Lifting the water with exhaust pressure diminishes the engine's ability to breathe, although in a properly designed system, not much. See last paragraph for an odd quirk about this.

A waterlift system injects the water ahead of the muffler by means of a mixer, usually an inline type like Moyer sells or a mixing elbow like the Westerbeke or Yanmar. A standpipe system injects the water directly into the top of the muffler.

A standpipe muffler is always located above the waterline, a waterlift is usually below the waterline and often below the engine.

The odd quirk: we've gone 'round and 'round about exhaust hose size and whether bigger is better. With a standpipe system, bigger is better, no question. A waterlift however, reaches a point of diminishing return. As the designed exhaust hose gets larger, so does the water 'batch' the exhaust is trying to push uphill resulting in more backpressure. In this case, the larger hose creates more pressure, the opposite of what you'd think. Strange but true. The optimum design is a hose big enough for the engine to breathe but not too big. Based on a recent poll, it's somewhere between 1 1/2" and 2".

Hope this helps.

[Mark S]

Our 1969 Pearson 35 still has the copper standpipe which I believe to be original equipment, although our late model A4 is probably not original to the boat. There's a post from late 2008, I think, that diagrams how the standpipe system works. We've had no trouble with it and to my knowledge neither did the PO. Having said that, knock on wood.

[ArtJ]

Yeah Art, understand how it could be confusing.

First, the term 'riser' is used for a variety of things. In our exhaust systems it simply refers to a pipe going up, a component of the system. I used the term over on the 'no more fouled plugs' thread to accurately describe a vertical structural component (bulkheads are perpendicular to the centerline, risers are parallel).

You are correct that the raw water must be lifted to a point higher than the waterline in all marine exhaust systems (except keel pipe/dry stack systems that don't pump raw water aboard and therefore don't have to expel it but we're not going there). In the standpipe system the water is lifted by the raw water pump. The waterlift system uses exhaust pressure to lift the water, hence the name. Lifting the water with exhaust pressure diminishes the engine's ability to breathe, although in a properly designed system, not much. See last paragraph for an odd quirk about this.

A waterlift system injects the water ahead of the muffler by means of a mixer, usually an inline type like Moyer sells or a mixing elbow like the Westerbeke or Yanmar. A standpipe system injects the water directly into the top of the muffler.

A standpipe muffler is always located above the waterline, a waterlift is usually below the waterline and often below the engine.

The odd quirk: we've gone 'round and 'round about exhaust hose size and whether bigger is better. With a standpipe system, bigger is better, no question. A waterlift however, reaches a point of diminishing return. As the designed exhaust hose gets larger, so does the water 'batch' the exhaust is trying to push uphill resulting in more backpressure. In this case, the larger hose creates more pressure, the opposite of what you'd think. Strange but true. The optimum design is a hose big enough for the engine to breathe but not too big. Based on a recent poll, it's somewhere between 1 1/2" and 2".

Hope this helps.

Thanks for the great explanation

Regards

Art

[tartansailboat]

standpipe construction

Nduttion, thanks for the clear explanation, now I have a question regarding the optimum pipe ID size for a water lift system. I am about to replace the hot section of my (Moyer) water lift system and have found reasonably priced 316L pipe components from McMaster Carr for 1 1/4 pipe. They show two wall thicknesses, one Schedule 40 and the thicker wall, Schedule 80. The thicker wall decreases the pipe area by about 15% but affords greater lifetime. From you comments, I gather that I do not want to decrease the pipe area any more than necessary, is that correct?

[ndutton]

Nduttion, thanks for the clear explanation, now I have a question regarding the optimum pipe ID size for a water lift system. I am about to replace the hot section of my (Moyer) water lift system and have found reasonably priced 316L pipe components from McMaster Carr for 1 1/4 pipe. They show two wall thicknesses, one Schedule 40 and the thicker wall, Schedule 80. The thicker wall decreases the pipe area by about 15% but affords greater lifetime. From you comments, I gather that I do not want to decrease the pipe area any more than necessary, is that correct?

Hopefully avoiding one of my notorious lengthy posts, I'll try and hit the marks. Please know that these are my opinions and around here opinions vary.

Optimum pipe size
There was a poll last year on this subject and if I recall, 1 1/4" pipe was the most common. Note that the A-4 exhaust flange is 1 1/4" as is the Moyer mixer and many of us have that size hot section with excellent performance. I don't think anyone is running smaller than 1 1/4". Others strongly advocate larger sizes to 2". Be sure to read the 'odd quirk' in the previous quote.

Sch 40 vs. Sch 80 pipe
You're talking 316 stainless pipe so I think sch 40 will last a lifetime as it is.

[tartansailboat]

standpipe construction

thanks Ndutton, the 316 listed in McMaster Carr was 316L for low carbon and I think that alloy is very corrosion resistant. For my hot exhaust section, one 4 inch nipple, one 3 1/2 inch nipple and two elbows the cost was about $40, cheap enough once you consider the labor involved. I will stick with the thinner schedule 40.

[ndutton]

Tom,

The failure of the stainless in only one particular area of the hot section and not others is most interesting.

Regarding your new brass hot section, for reasons unknown to me it's non compliant with ABYC standards, section P-1, table 1 found on page 6 of the following attachment. According to them, after the water injection point you're good with brass but not before. Maybe something to do with strength/heat issues as you mentioned.

http://www.ntsb.gov/Dockets/Marine/DCA97MM012/234864.pdf