Vessel Sink Height and Venting

Hey, guys. Something occurred to me the other day. Vessel sinks have made it into the home centers, meaning that DIY'ers will be buying them and replacing their existing in-counter lavs with them. Most of the vanities I've seen for vessel applications end up putting the flood rim of the vessel at around 36" above-finish-floor rather than the 32" a.f.f. as one might see with more traditional lavs.

Of course, there are plenty of situations out there, such as a sink installed against a knee wall, or a sink installed under a window, where the vent for the sink goes horizontal at 38" a.f.f. (meeting the 6"-above-flood-rim rule for a 32" high sink). But replacing the traditional lav with a vessel sink with a 36" flood rim would put the vent out of compliance.

Has anyone run into this issue? Is everyone installing horizontal vents at 42" a.f.f. now to accommodate vessel sinks? I'm guessing the code councils, and generations of plumbers, didn't bet on sinks becoming 4" higher all of a sudden!

a vent can run horizontal below the flood rim as long as you use drainage fittings, slope it towards the drain, and don't tie into another fixture vent until you bring it 6" above the flood rim of the higher fixture. When roughing in vessel sinks I usually bring the drain up to the side then run the trap arm to the sink center.

vent

That is the very reason that vents cannot tie together, and when possible should not offset , below 42". Even though a toilet's flood rim is only 17" max above the floor, you never know when someone is going to make a revision and connect something else to its vent.

hj said:

That is the very reason that vents cannot tie together, and when possible should not offset , below 42". Even though a toilet's flood rim is only 17" max above the floor, you never know when someone is going to make a revision and connect something else to its vent.

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Vents can't tie together? What plumbing code prohibits that? just curious.

Not below the flood level of all the fixtures being tied together.

Terry said:

Not below the flood level of all the fixtures being tied together.

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I believe I stated that, the reply was that it was illegal to tie vents together. Was just curious because I stated the requirement to be above the flood rim.

vents

You have to read the entire sentence. It was that you cannot tie them together below 42".

hj said:

You have to read the entire sentence. It was that you cannot tie them together below 42".

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If the flood rim of the fixture is 31 inches like a normal lav, then you can tie in at 37.

winslow said:

If the flood rim of the fixture is 31 inches like a normal lav, then you can tie in at 37.

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Not according to the code. The code reads 42" or 6" above the flood rim, WHICHEVER IS HIGHER.

hj said:

Not according to the code. The code reads 42" or 6" above the flood rim, WHICHEVER IS HIGHER.

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which code is that? not trying to be a tool, just cutious.

code

Every one I have ever seen. The 42" is a minimum because even though the original fixture could have a 17" flood rim, there is no way to know if someone, some day, will connect a 36" high sink to it, at which time the 42" level would be required. If the fixture has a higher than 36" flood level, then the 6" above it becomes the requirement.

hj said:

Every one I have ever seen. The 42" is a minimum because even though the original fixture could have a 17" flood rim, there is no way to know if someone, some day, will connect a 36" high sink to it, at which time the 42" level would be required. If the fixture has a higher than 36" flood level, then the 6" above it becomes the requirement.

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I'll take your word for it, but the UPC doesn't say that. I'm only familiar with the UPC as that is what juristriction I am in.

905.3 Unless prohibited by structural conditions,
each vent shall rise vertically to a point not less than
six (6) inches (152 mm) above the flood level rim of
the fixture served before offsetting horizontally, and
whenever two or more vent pipes converge, each
such vent pipe shall rise to a point at least six (6)
inches (152 mm) in height above the flood level rim
of the plumbing fixture it serves before being
connected to any other vent. Vents less than six (6)
inches (152 mm) above the flood level rim of the
fixture shall be installed with approved drainage
fittings, material and grade to the drain.

i have always heard 42" minimum

thank you for posting that. I oo always heard 42" minimum.