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How to Change Your Water Heater


  • Hacksaw or pipe cutter
  • Pipe wrenches
  • Screwdrivers
  • Adjustable open-end wrench
  • Drill and 1/8 inch bit
  • soldering torch
  • appliance cart, dolly, or hand truck


  • Water heater
  • T&P relief valve
  • Vent pipe fittings
  • Gate valve
  • Water, Gas Pipe
  • 1/2 inch flare adaptor
  • Teflon plumber's tape
  • Stick pipe dope
  • Garden hose
  • Sweat soldering supplies
  • 240-volt neon test light
  • Hand cleaner

Removing Your Old Water Heater

The typical overhead-plumbed water heater hookup is shown. Before you can connect the new heater, though, the old one must be taken out. 

Begin heater removal by turning off the gas or electricity to the heater. Drain the heater. Opening a hot water faucet will let air into the system. On a gas heater, separate the vent pipe from the draft hood. It should lift off after removing the sheet metal screw that holds it. After making sure the pilot light is out, disconnect the gas line at the heater and cap it. Next, remove the heater from its water piping. If connected with unions--removable threaded fittings--take them apart with a pair of pipe wrenches. Pipes without unions will have to be hacksawed off. Or a pipe/tubing cutter will do the job. The old heater can now be taken away and disposed of at a dumpsite.

    Installing the New Heater

    Take your new heater to its location by "walking" it or using an appliance cart, dolly, or hand truck. Position the new heater so your piping--particularly a gas vent pipe--will reach most easily. Install the heater's new draft hood (gas heater). Many have legs that insert into holes on the heater's top.

    Every gas water heater needs proper venting that's no smaller than the draft hood collar of the new heater. It's a good idea to use new vent pipe elbows, as the old ones will probably be corroded at their present angles. The vent should go straight up as far as possible. Then any horizontal run should slope upward at least 1/4 inch per foot. Connect the vent pipe with short sheet metal screws.

    Now you can make the hot and cold water connections. The easiest way often is using copper flex-connectors, available from your dealer. Figure 7 shows how flex-connectors fit a heater's female tapping (left side), or male stub (right side). At the upper end, the flex connectors make up to a threaded metal pipe (left) and a sweat-soldered copper tube (right) using a male adapter. They range in length from 12 to 24 inches--the 18- and 24-inch lengths being most practical. Flex-connectors are easily bent to reach where you wish.

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    How the hot water piping is handled depends on whther your house has threaded metal, sweat-soldered coper, or thermoplastic piping, and whether it is 3/4 inch or 1/2 inch. No matter what, though, the old heater should be fitted with a cold water gate valve. To keep it from becoming sediment-fouled, the valve should be placed in a vertical section of piping.

    Use Teflon tape (but not pipe dope) on the male threads entering flex-connectors. If your water heater has female-threaded tappings, you'll need a pair of short 3/4 inch nipples to accept the flex-connectors at the bottom. If the heater comes with 3/4-inch male-threaded stubs, the nipples are not needed. At the top, the flex-connectors fit directly to the ends of threaded pipes (or a male adapter sweat-soldered to copper tubing). Some install to copper tubing without sweat-soldering, an advantage. If you sweat-solder, be sure to do this before installing the flex-connectors, as the heat from soldering would damage the connector gaskets.

    Thermoplastic pipe. Flex-connectors are not necessary with CPVC or PB plastic pipe. Needed are what's called "transition unions" to go between the metal heater threads and the plastic piping. Some manufacturers of plastic fittings also call for the use of foot-long threaded steel nipples between the water heater and the transition unions to distance them from conducted burner heat. Two more transition unions are needed at the top end where the plastic risers will join the threaded metal water lines (not required if your house is plumbed with plastic tubing). You can use rigid CPVC tubing, solvent welding the joints. Or use flexible PB, joining with mechanical couplings. PB cannot be solvent welded. And don't try to hook up a water heater with PVC, PE, or ABS plastic piping, as these will not take hot water.

    Relief System

    A vital part of water heater installation is the provision of a temperature and pressure relief valve and relief line. The relief system is designed to let off excess heat and pressure automatically.

    With all the plumbing connected, you can close the heater's drain valve and open the cold water inlet valve to fill the storage tank. Opening a hot water faucet will release trapped air in the top of the tank. Close the faucet soon so water flows readily from it. Check for leaks. 

    Energy Hookups

    The very last thing to do is connect the gas or electric lines to your heater.

    Gas connections. Install a 1/2 inch male flare adapter into the inlet opening of the heater's gas valve. Connect the gas flex-connector collar to the flare adapter (no dope or tape) and tighten with an adjustable open-end wrench. Everything okay, see that the thermostat is in the off position. Then you can turn the gas on.

    Electrical connections. The wires serving an electric water heater must be the right size, providing the voltage and amperage the heater is designed for. Unless you know how to work with wiring, a qualified electrician should be hired to wire the heater. When you turn the heater circuit on, check the electric meter to see whether it is spinning, indicating that the heater is working.

    NOTE: Using flexible gaspipes is against most local building codes. Likewise, electrical connections MUST be to code for safety. See photograph for illegal connections..

    Call us and we will be happy to provide a free quote to replace your existing water heater. All of our installations conform to local building codes.

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