Water heaters

How old is my GSW / John Wood water heater?

GSW / John Wood water heaters carry the build date inside the serial number. We know 2 serial formats for this brand; the decoder tries each one and shows every reading that fits.

How to read a GSW / John Wood serial number

Year and month (through 2007)

Skip a leading letter. The first two digits are the year and the next two are the month.

U0106413635 reads as June 2001.

Two sources agree Building Intelligence Center, InspectAPedia, InterNACHI water heater dating chart

Year and week (2008 to today)

Skip a leading letter. The first two digits are the year and the next two are the week.

U0928413635 reads as week 28 of 2009.

Two sources agree Building Intelligence Center, InspectAPedia

Where to find the serial number

Water heater: the rating label on the side of the tank, near the EnergyGuide sticker. On a tankless unit it is on the side or bottom of the cabinet.
Use the line marked Serial No. or S/N, not the model number. If the plate prints a manufacture date, use that.

How long should it last?

Typical life of a tank water heater: 8 to 12 years

A standard tank water heater usually lasts 8 to 12 years. Some make it to 15 with soft water and a replaced anode rod; some fail at 7.

How long does a tank water heater last? · Should I replace my water heater? · DC Dept. of Energy & Environment, InterNACHI

Should I replace it?

Should I replace my water heater?

Other brands in this group

A.O. Smith · American Water Heater · U.S. Craftmaster · Bradford White · State · Reliance · Kenmore · Whirlpool · Rheem · Ruud · Richmond · GE · Marathon · Rinnai · Navien · Noritz · Takagi · Bosch (tankless water heater) · Lochinvar · Paloma · HTP / Westinghouse / American Standard (water heaters) · Giant · EcoSmart / Eemax · Stiebel Eltron

Parts that help it last

Anode rod The sacrificial rod that rusts instead of the tank. Checking it every few years is the cheapest way to add life.
Flush kit A hose and fittings for draining sediment from the bottom of the tank once a year.
Expansion tank Soaks up pressure swings in a closed plumbing system. Ask a plumber whether yours needs one.
Leak alarm A small alarm that goes on the floor beside the heater and warns you before a slow leak becomes a flood.

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Keep a record of your home

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