I think they call that "wild pilot". Beyond that, I'm not a lot of help.
Might be able to get a new valve by way of the make and model number of the
heater. Or numbers on the valve itself. Or take the valve in hand, and go to
the parts house and say "got one of these?"
Christopher A. Young
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Have very old gas heater in pumphouse. Smelled gas the other day; got
to doing the look-for today. Turns out it's the stem seal around the
shaft on the valve at the heater; this heater is too old to have
integral control valve like a modern furnace, the valve body has a
second small control valve for the pilot line.
Anybody else here old enough to remember such and have any ideas on
replacements? I've shut main off at the moment; since it's 80F this
week won't need it any time real soon now and probably can get by until
next winter now, but it'll need fixing at some point.
I don't want to touch this one at the moment until have a plan of action
in case I can't rebuild the stem seal...
OBTW, it's 3/8" NPT...