Maximum water heater vent horizontal run

[Jon mackay]

Does anyone know the rule for the maximum horizontal length of a natural draft water heater vent?
Here are some pictures of a run that is a total of 16' from the water heater to the chimney. The pipe is a 4" that meets another 4" from a furnace into the 5" Y and then 8" for about 4' into the chimney.
I am thinking the water heater should be moved or (more likely) switched out to a high efficiency system and vent out the sill area...

Scorching above the water heater burn chamber and I believe the vent above the water heater should run a 12" minimum vertical before a 90 degree bend is allowed.

[Phillip Smith]

Code check says the length should be no more than 75% of the total developed height,

[Jon mackay]

So with a run of 16' the total developed height would have to be approx. 21.3' just a bit off then.. Its probably 4' developed height at best.
Is that the same for furnaces with only an inducer fan also?

[paul hardy]

that is the total height of the chimney from the draft hood tothe top of the chimney above the roof.

[Jon mackay]

Ah.. yes... I thought I was missing something..

So it does meet that requirement. Hmm.. I wonder what woul cause the scorching. The initial transition from the water heater to the horizontal run is almost an immediate 90.. If I'm not mistaken, it should rise a minimum of 12" before taking that 90. That may be the problem here..

[mike brown]

Hard to tell in your picture, but it looks like the union on the gas piping is before the gas valve instead of after it. Might want to check that as well. That doesn't meet code here in ny.