Not following. Where do yo suggest inserting a new valve that wouldn’t require shutting the water outside? No idea where the outside valve is.
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beween the main ant the meter - or after the meter if you need to.
if the water co needs to replace the meter, they'll take care of the leaky main issue.
(or just let it leak while they do it)
in the mean time, you are just looking to isolate the house.
is it iron pipe or copper? If it is copper after the meter, you can slide a
sharkbite valve in there. Or a compression fitted valve ($15 at HD.)
(there is a kit for doing a sweat valve on a leaky pipe - it is a plug that slides through the valve, but $$$)
If it is iron, that is a bit tougher, cause you'd need to fit pipe to the next joint (i have an iron pipe threading kit, but it is probably near an elbow so pieces are available.)
Would also require a pipe union, cause nobody got time for a reverse thread nipple.