I had a plumber from our home warranty company tell me that the pressure regulator that failed wasn't covered because sediment in the hot water heater caused the failure. He didn't even look at the hot water heater which is less than 1 year old. Sediment is the only thing not covered on our warranty when the entire plumbing system including pressure regulator is 100% covered. Is it possible to have a hot water heater cause this failure?

Well, If he didn't run water out of the drain cock of the H/W tank, how would he know there was sediment in the bottom of the tank?

Is the H/W tank covered under the warranty?

Did he disassemble the PRV to determine that there was in fact debris lodged in the seats?

If so, was the debris in the first or second stage of the PRV?

How did he determine that the source was from your side of the system, rather than from the Utilities side of the system?

Also, I find it very suspect that sediment somehow managed to make it's way up through the dip tube of the H/W tank, past the one way heat trap nipple of the tank, fighting the effects of the incoming water pressure all the while, only to lodge in the seats of your pressure reducing valve.

Sounds like a load of hooey to me.

For a time I worked for a home warranty company, basically it was in their best interest to have me turn the warranteed call into a non-covered call. I did not do this and I was released. The prv is on the cold side. Sediment from the water heater can not get to the prv. Sediment is what is at the bottom of the water heater. If you had something clogging the prv it would be termed as debris.
File a complaint with the home warranty company and have them send a different plumber out. You may have to call an independent company to actually do the repair and then try to get the warranty company to pay.

We are talking about a house PRV( pressure relief valve) and not a P&T valve(pressure and temperature ) on the heater aren't we? If so then I'm with growler, and I quote, " Also, I find it very suspect that sediment somehow managed to make it's way up through the dip tube of the H/W tank, past the one way heat trap nipple of the tank, fighting the effects of the incoming water pressure all the while, only to lodge in the seats of your pressure reducing valve."
Well I don't find it "supect" that it happened. I find it "damm well impossible".
For it to happen like that, first the water pressure out in the city main
Would have to drop to zero and began to run backwards creating a suction that would pull the water in the house piping out in the main. Now this would affect ALL the houses connected to the main.
Couple this to the fact that the sediment in your water tank would have to be built up over the dip tube to suction it out and the fact that the plumber didn't even take the time to open the boiler drain and check for sediment t6his tells me the plumber only looked at the home warranty companies interest and not yours. Fight it! You have a case that's based in reality while theirs is based in fantasy and supposition. For a clincher call the water company and ask if any pressure failures occurred on the date in question and you gottum by the gonards. Good luck, Tom