[paulrosh89]

Hi I'm a property manager overseeing several 4-6 unit apartment buildings, most of which have all their water heaters located in the basement. We're arriving at our season for annual water heater maintenance and I'd like to know if it's possible to drain the tank and refill it without trapping air in the pipes and needing to enter the apartment to open a faucet. During recent maintenance of each individual unit we've already cleaned all faucet aerators and I'd like to avoid sediment getting caught in them so soon. In the future maybe we need to perform water heater maintenance at the same time as the faucet inspections but for this occasion I'm wondering if there's a loophole.

[hkstroud]

You do not want to DRAIN the water heaters. You want to FLUSH the water heaters. There is a difference.
To drain, you would turn off the stop valve on the incoming water line, open the drain valve and open a hot water faucet somewhere to let air in, so the water in the tank can drain out. To refill you would close the drain valve, open the incoming stop valve and let the incoming water push the air out the hot water faucet. That would carry some sediment in the tank out as the tank drained. But the force of the water coming out of the drain valve would only be as much as the weight of the water in the tank could create.
To flush the water heater you simply attach a hose to the drain valve and open it. Letting the pressure of the incoming water line force the water in the tank out the drain. Naturally, this will be with much greater force and speed, than just letting it drain. It will carry away more sediment in the bottom of the tank than just draining. Simply let water run until it is clear. There will be no air in the tank so no need to purge it