Plumbing in the Home/Water Heater question


Mr. Nicholas,
I've got two gas hot water heaters (A.O. Smith  40 gallon), and one of them needs the pressure valve replaced.  I THINK the two water heaters are hooked up in series, but they may well be hooked up parallel.  I know replace the temp/pressure relief valve...I need to: (1.) Turn off the gas, 2.) Turn off the cold water inlet, and then (3.) Release a little water out of the reservoir via the bottom spigot just to be safe.  My question:  To replace the pressure valve on just one of the hot water heaters, do I need to release pressure and water from BOTH of them?  (I know I'll need to turn off the gas and cold water to both.)  And does the correct procedure change between a series vs. parallel connection?

The  procedure to use whether they are series or parallel piped is the same. By that I mean the steps to take are  to either set the heaters to pilot or off position, turn off the cold water supply( parallel set up will usually have two cold water supply valves - one for each tank) then relieve the pressure. The simplest way to do that is to open a hot water faucet and let it run until it stops by itself. Then open the old relief valve to be sure the pressure is down. Replace the defective valve, turn on the cold and fire the unit(s)
One note  - if you relieve the pressure by using a faucet, be sure to close the faucet before removing the old pressure relief valve.


Plumbing in the Home

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Jay Nicholas


Plumbing & Heating (warm air, hot water & steam heat)


40 years in the business, 40 years as a lic. master plumber in NY State. Retired

Graduated Magna cum laude at the School of Hard Knocks

Past/Present Clients
Commercial, residential and light industrial. You name it ...I have probably worked on it

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