I have a six years old A.O. Smith model GUR40 400 water heater. A couple of plumbers I've talked to about replacing the anode rod say they only replace water heaters and don't do repairs. I was hoping to extend the life of this water heater. Do most plumbers not handle replacing an anode rod?
How much would you expect to pay for that? (I am not a plumber)
One problem for the plumber is that the last one to touch a device often gets blamed.
If you get a tooth cleaning, and a tooth disintegrates a month later, the dentist does not generally get blamed. Yet in the case of the plumber who changes an anode rod, I am not so sure that will be the case.
Regarding the job, you usually need an impact wrench to loosen the anode that has been in service for many years, if that has a hex head 1-1/16 bolt. I don't know what difficulties occur if your WH has the anode as part of the hot nipple.
Now is the impact wrench going to have a negative impact on the WH life (such as cracking the glass lining)? I don't know. I broke the cheap HF air impact wrench trying to remove an anode that had been in service over 10 years. I returned that and got their next size up. That barely did the job.
I put in a powered anode. That went bad after a few years, and the part got replaced by an upgraded model under warranty. So far, so good. Swapping out the powered anode was much easier than the original anode, because I used a lot less torque when I tightened the powered anode. They use a whole lot more torque than they should (IMO) when they tighten the sacrificial anodes at the factory.
If you get a new WH, and plan to change the anode later, you might consider pulling the anode on the new WH, add tape, and tighten to maybe 15 ft-lb. Replacement should then be pretty easy when you get around to it.
Some well owners in some areas, and the plumbers who install the WH, will remove the anode when new and replace that with a brass plug. This is to prevent H2S generation with well water. OK, I only know one person who's plumber does that, but it is a thing. A powered anode is much better than a plug, and it will not contribute to H2S generation.