It appears that the faucet stem seats in this Eljer bathtub faucet (bought & installed in 1975) are plastic (or nylon). When I tried removing them with a standard faucet seat wrench they would not budge. It appears that the hole is hexagonal, but the wrench started to round the hole so I stopped. Any ideas?
Are you just replacing them with new ones and have replacements on hand? The old ones have most likely calcified in place and if they don't budge (and you have the right wrench - sometimes they are square and not hexagonal), find a flat head screwdriver with the blade wider than the inner space of the seat. Stick the screwdriver inside and give it a good push till it feels that it grabbed the plastic pretty well. The large screwdriver most likely has a slot in its handle where you can insert another, smaller screwdriver to give you additional leverage when you turn. Turn it slowly counterclockwise. If it strips again, drive it further in but be careful not to drive it so far as to damage the threads of the faucet.
If the flat head screwdriver trick does not work, I would be tempted to just break them off. Make a couple of deep cuts with a good pair of snips (you can simply extend the damage the blade of the screwdriver has already done) , then take some sturdy needlenose pliers, bend and grab a little corner and start twisting it until the cut grows through entire length. Be careful not to damage the threads on the faucet.
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