Just had 3cm granite counter tops installed and found that the shanks (water supply connections) were to short. Bummer!!! Couldn't find a fix on the internet except ordering some extension which would mean at least a week or more to order or drive 50 miles to a larger town that might have them in a large plumbing supply house.
Well folks here is the fix, easy and cheap. After much thought I realized with help of a semi-retired plumber friend of mine.
You need to think electrical not plumbing, get off the plumbing isle and go to the electrical isle. There you should be able to find an electrical conduit nut called a 3/4" lock nut (thread size of the shank), with that and 2 thin reducer washers (to get from the 3/4" pipe size to larger than the hole in the counter top) which would normally be used to reduce the size of a hole in electical boxes. This will reduce the new nut assembly to less than 1/4" which in turn gives you an additional + 1/4" of thread on the shank which in my case was way more than enough. They do make a thin single washer called a "fender washer" but I couldn't find one in our hardware store. When making the new install center the holes up using one of the plastic washer to secure the faucet to the top. Then put the newly created washer/nut on the other shank(s) and secure. Check now to assure this has given you the additional threads needed, if it has remove the plastic nut/washer and install your other new assembly. Use a screw driver and a hammer to tap the ears on the lock nut to make your final tightening of the assembly, now you can throw away the thick plastic washer/nuts the manufacturer supplied. Thought about packaging these and selling them for $15-20 BUCKS like they get for extensions but didn't. Your total cost per shank should be about $1.50 each. In addition to this you may want to put an antiseize grease on the area where the lock nut will reside to help prevent corrosion since the two metals have an electrolyisis reaction with each other and make the nut very difficult to remove should you need to do that later. Hope this helps.



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Are you sure of the 3/4 in size? The shanks with the integrated water supply are usually 1/2 in straight pipe thread, so a 1/2 in electrical lock nut will fit.

No amount of grease or antiseize will help in the long run and any moisture present will rust up the steel nuts. Plastic locknuts are available



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i've gone to too many calls where the owner says "the faucet is loose, will you tighten it from below".. as george said, corrosion from below. steel washers and nuts seem like a good idea but will not last and when removal of the faucet needs to be done, they will need to be cut away.