In article ,
Ariel writes:
I have a very slow gas leak in my house that I simply can't find.

The gas is leaking at a rate of 1.7 cubic feet per day (0.071 cubic feet
per hour) as measured by the meter.

Have you tried closing all the appliance isolator valves to see
if one of them stops the leak?

I don't smell gas anywhere, and I have looked at (sniffed actually)
every joint I could reach, and nothing.

A leak inside a room sealed appliance would not generate a gas
smell inside the house, but outside at the flue terminal.
Likewise, if the meter is outside, check for leaks in the
pipework before it enters the house.

My question is how sensitive of a detector would I need in order to find
this? I have seen detectors with ppm sensitivity ranging from 50 to
2000. Obviously price goes accordingly, how sensitive of a detector do I
need?

And realistically speaking, how bad of a leak is it? I know that any
leak at all sounds scary, but a leak so slow that you can't smell it is
not a fire hazard as far as I know, but it does waste gas.

This is very unlikely to generate an explosive mixture. It would
have to be leaking into a small rather well sealed cavity in the
building structure at your leak rate (assuming meter is accurate
at such a low flow rate) to form an explosive gas/air mixture.

Have you tried gas leak detector spray, e.g. a can of LD-90 which
should be relatively cheap? This will generate a small clump of
white foam at a leak after some minutes which might be easier to
see than smell.

You could call Transco. If they can find and fix the leak in 30
minutes, I think it's free, but otherwise they'll disconnect you
after verifying it's not their meter or couplings at fault.

--
Andrew Gabriel