Following is a idealized anatomy of a hot water heater replacement and recommended maintenance performed, basically, on the Internet, in real time, with the help of everyone here.
This procedure, which combines the best found on the Internet and which takes into account *every* single of the hundreds of replies in this newsgroup, is posted with the hope that the next amateur replacing their natural gas galvanized pipe home hot water heater prints this out and follows it to their delight and benefit!
A complete set of photos of every step below is available at
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Here it is... this is an idealized version of my experience last week!
If you have old galvanized pipes, consider these preventive steps:
- Remove all debris screens from faucets, & tubs to prevent clogging
- Shut water to dishwaswher to prevent clogging of dishwasher screens
- Remove tub valves (I think) to prevent clogging of tubs
Remove the hot-water heater:
- Shut off the natural gas at the main gas meter (optional)
- Shut off the natural gas at the local hot-water heater (mandatory)
- Wait for the pilot light to go out to ensure no gas is left in the line
- Turn the thermostat on the hot-water heater to the off position
- Wait overnight, if possible, to allow the hot water in the tank to cool
- Or run 10 or 20 gallons of hot water in the house to dilute the tank
- You will be very glad you cooled the water in the tank: Trust me!
- Shut off the main household cold water (if replacing the gate valve)
- Shut the cold-water gate-valve right-side inlet to the hot-water heater
- Open at least one hot-water faucet in the house to drain off pressure
- Open the temperature and pressure valve as a safety measure (optional)
- Unscrew the cold-water inlet at the nipple at the top of the tank
- Unscrew the hot-water outlet at the nipple at the top of the tank
- Use two wrenches on flex connectors or they twist like a phone cord!
- Unscrew the natural gas inlet to the water-heater thermostat
- Cap the newly disconnected natural gas line to prevent contamination
- Connect a garden hose to the plastic hot-water-heater drain valve
- Open drain valve to drain hot water where it will not damage anything
- If 40/50 gallons doesn't come out something is clogged (very common)
- Shake and prod and push to get the water out (it happened to me)
- Otherwise you'll be moving a full tank which can tip (it happened to me)
- Disconnect garden hose and close drain valve when done (40 or 50 gallons)
- Unscrew the sheet-metal screw holding the vent pipe to the draft hood
- Separate the vent pipe from the draft hood (the hat on top middle)
- Unscrew sheet-metal screws holding gas-flue hat onto the vent pipe
- Separate the vent pipe from the gas-flue hat on top center of your heater
- Unscrew the seismic straps (if any) as the last thing before removal
- Remove old heater off the elevated base with two people and a handtruck
- Remove all water plumbing up to and including the old shut-off valve
- Remove all gas plumbing up to and including the old shut-off valve
Replace hot-water heater: WHILE THE NEW TANK IS SITTING (DRY) ON THE GARAGE FLOOR:
- Remove the heater from the box by cutting the box completely open
- Replace the plastic drain valve with a brass ball valve (optional)
- Install the new temperature and pressure (T&P) relief valve (if needed)
- Note: The brass T&P relief valve may already be installed on your tank
- Install the cold water dialectric check-valve nipple (on the top right)
- Install the hot water dialectric ckeck-valve nipple (on the top left)
- Note: The 2 check-valve nipples may already be installed on your tank.
- Wrap three layers of teflon tape on each dialectric check-valve nipple
- Remember: Always use 2 wrenches when screwing & unscrewing pipe fittings!
MOUNT THE TANK & POSITION THE VENT AND HOOD:
- Mount and level the new hot water heater on the 18-inch elevated base
- Ensure at least six inches of clear space all around the new heater
- Hacksaw the old gas vent so that it fits the new larger water heater
- Ensure the gas vent aligns with the center of the hot-water heater
- Insert legs of the draft hood into the holes in the top of the heater
- Drill a 1/8 inch hole into the draft hood and 3-inch vent pipe
- Screw in at least 1 sheet-metal screw from the vent hood to the vent pipe
ATTACH THE COLD WATER INLET:
- Wrap Teflon tape on the threads of the fittings supplied with the tank
- Insert a blue heat-trap fitting (arrow down) into the cold-water inlet
- Ensure the last two threads are never covered with Teflon tape
- Look end-on through all fittings to ensure no Teflon tape overlap
- Do not use pipe dope on any threads where Teflon tape is noted below
- Screw the cold-water inlet male:male nipple into the top of the tank
- Wrap Teflon tape on the thread of the galvanized 3/4" water-inlet pipe
- Screw a dialectric union on the 3/4" galvanized cold-water inlet pipe
- Check for Teflon tape on the threads of each male:male brass nipple
- Screw the brass male:male nipple on the female:female dialectric union
- Screw a new ball-valve shutoff onto this vertical cold-water inlet pipe
- Wrap Teflon tape on the threads of another male:male brass nipple
- Screw this male:male nipple into the new ball-valve shutoff
- Screw the copper flex pipe onto the cold-water inlet brass nipples
ATTACH THE HOT WATER OUTLET:
- Wrap Teflon tape on the threads of the fittings supplied with the tank
- Ensure the last two threads are never covered with Teflon tape
- Do not use pipe dope on any threads where Teflon tape is noted below
- Insert a red heat-trap fitting (arrow up) into the tank hot-water outlet
- Wrap Teflon tape on the thread of the galvanized 3/4" water-outlet pipe
- Screw a dialectric union on the 3/4" galvanized hot-water outlet pipe
- Wrap Teflon tape on the threads of each male:male brass nipple
- Screw the brass male:male nipple on the female:female dialectric union
- Screw a new one-way check-valve onto this vertical hot-water outlet pipe
- Wrap Teflon tape on the threads of another male:male brass nipple
- Screw this male:male nipple into the new ball-valve shutoff
- Screw the copper flex pipe onto the hot-water inlet brass nipples
- Bend the copper flex pipe into an S shape to further inhibit heat loss
ATTACH THE T&P SAFETY PIPE:
- Screw on rigid high-temperature water pipe to the T&P valve
- The open outlet must be six inches (no more, no less) from the floor
- The open outlet must not be threaded; no valves or traps are allowed
- Place a bowl or bucket at the outlet of this open overflow pipe
- Test the T&P valve & plumbing by flipping the little aluminum lever
- Scalding hot water should sputter out of the pipe outlet
TURN ON THE WATER SUPPLY:
- Optionally, remove all the screens from your water faucets
- Optionally, shut off the water to your dishwasher to prevent clogging
- Optionally, remove the shower heads to prevent clogging
- I'm not sure what to remove yet to prevent your tub from clogging
- Open at least one hot-water faucet in the house to bleed out air
- Slowly open the main cold-water input to the house
- Open the new ball-valve cold-water input to the hot-water heater
- Check for leaks in the plumbing as the tank fills
- Place a pan or bowl at the T&P overflow tube & test the T&P valve
ATTACH THE NATURAL GAS INLET:
- Always connect the natural gas line as the very last step in this process
- Set the thermostat on the hot-water heater to the off position
- Coat male natural gas line threads with stick pipe dope (no teflon)
- Ensure the last two threads are not covered with any pipe dope
- Connect the new (yellow) natural gas flex pipe to the thermostat
- Turn on natural gas at the main switch (if it was turned off)
- Turn on natural gas at the local inlet to the water heater
- Test for leaks by toothbrushing a solution of dish detergent and water
- Read and carefully follow the manufacturer's lighting instructions
INSULATION:
- Wrap additional insulation around your hot-water heater, if desired
- Wrap insulation around your hot-water outlet pipe, if desired
DISPOSAL:
- Perform an autopsy on the old water heater by removing all plumbing
- Remove & inspect the 1 1/16 inch 3-foot 8-inch sacrificial anode
- Remove & inspect the T&P valve
- Call the local garbage or recycling to haul away the old water heater
Twice a year:
- Clint combusion-air lint screens (at the bottom inch of the water heater)
- Place a pan or bowl at the temperature & pressure valve overflow tube
- Test the T&P valve by flipping the lever as water violently sputters out
- Turn the natural gas to the PILOT setting (or shut it off completely)
- Leave the cold-water intake valve open at the top right of the heater
- Open at least one hot-water faucet on any level above the water heater
- Gently connect a garden hose to your hot water heater drain valve
- Route the open end of the garden hose where hot water won't damage things
- Open the lower drain valve to empty a few gallons of muddy hot water
- Shut the drain valve when that water runs clear (approx 10 gallons)
- Once every three years, remove the 1 1/16-inch sacrificial anode
- Replace the 3'8" sacrificial anode if corroded or calcium passivated
- To replace, bend the magnesium anode or replace with sausage links
- Turn the natural gas back on and ensure the burner is working properly