I have a Reliance Sta Kleen 805, model 840 NART 6 JW, Z21.10.1, 1987, serial D88280258. The thermostat-control valve has gone bad. Tell me how to get a replacement valve.
Do you mean the thermostat or the temperature pressure relief valve. Both items are standard repair items available at any do it yourself store. The T&P valve needs to be a long shank model to reach through the tank insulation.