State PRX 40 gas water heater

[jb8103]

We're checking mechanicals in an older home. We went to drain the water heater to check for sediment. Shut off the gas, shut off the cold water intake, opened a nearby hot water faucet at the laundry sink, attached a hose, and opened the drain valve. The water came blasting out like a fire hydrant. I had to turn the drain valve in to calm things down. The faucet in the laundry sink kept running at normal pressure, turning to cold water after a few seconds, but showing no signs of drop in pressure.

Is this typical? I was expecting a fairly-low pressure flow from the drain valve, and also that the faucet flow would taper off to practically nothing after a minute or two.

[RegUS_PatOff]

is there an Expansion (pressure) (5 gallon?) Tank on either the Cold Water input or the Hot Water line ?

[jb8103]

is there an Expansion (pressure) (5 gallon?) Tank on either the Cold Water input or the Hot Water line ?

Nope.

Never seen one except on hydronics systems, but then, I haven't seen much at all in this business.