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What are the most common installation mistakes with water heater replacement?

Saturday, August 4, 2018

When professional plumbers replace a water heater they know exactly how to do a safe, workmanlike installation. Plus, because it requires a building permit and final inspection by a municipal inspector, you are pretty well assured that the final product meets current safety standards. But if a homeowner or handyman replaces a water heater—skipping the permit and inspection because it seems simple enough to connect two water pipes and a gas line or electric cable and turn it on—it’s often a different story.

   An improperly installed water heater has the potential to explode violently, flood your home, deliver contaminated water, or shock you; so getting it right is a serious matter. Here’s our “Top 10” list of the  safety defects we typically find in a non-professional installation:

1) NO TPR VALVE DRAIN PIPE - TPR stands for Temperature and Pressure Relief, and it was quickly discovered shortly  after the automatic storage-tank water heater was invented in 1889, that if the thermostat failed to shut off the heat source, when the water finally boiled under the pressure in the tank a violent explosion would occur. It was not unusual for a water heater explosion to destroy a small house.

    Because the TPR valve spews super-hot water if it does open to release the tank pressure, the water needs to be directed downward to within about 6-inches of the floor or the ground outside, to avoid scalding someone standing nearby at the time of the discharge. The graphic below is from a State® water heater installation manual, about the importance of a correctly installed  TPR valve and discharge piping. Water heaters come with a TPR valve, but no drain pipe, because the configuration depends on where it is installed.

2) TPR VALVE  DISCHARGE PIPING INCORRECTLY INSTALLED - The pipe must be of equal or larger diameter than the incoming cold water pipe, unlike in the photo below. It should be rated for hot water use (PVC pipe is not), take the most direct route to where it terminates without any traps (U-shaped areas that will hold water), and the end of the pipe cannot be threaded—so it is not easily capped. Never, ever seal the end of a T&P discharge pipe.

3) NO WHEELSTOP OR PROTECTIVE BOLLARD OR A WHEELSTOP THAT IS TOO SHORT - If a gas water heater is installed at the end of a garage, opposite the garage door, there is the potential for a car to be accidentally driven into it, resulting in flooding or even explosion if a gas line is fractured. So a parking wheelstop or bollard in necessary in front of the water heater. A wheelstop that will fit between the wheels of a car, like in the photo below, is useless.

4) NO COLD WATER SHUT-OFF VALVE - Like any other plumbing appliance, a shut-off valve is required and it should be placed on the cold water side.

5) UNPROTECTED ELECTRICAL CABLE - The electric cable that runs from the wall to the water heater needs to be inside a conduit to be protected from damage. The conduit is typically the flexible type. If the water heater is installed in an attic or compartment, protection is not necessary.

6) DISCONNECT NOT IN-SIGHT OR LOCKABLE - When someone is repairing an electric water heater, they need to be sure that the electricity stays off for the duration of their work. If the main electric panel is within sight of the water heater, the water heater circuit breaker in the panel is acceptable. If the main panel is not within sight, then a disconnect switch, breaker, or pull disconnect box needs to be installed near the water heater OR a locking device installed on the water heater breaker in the main panel.
   Also, there is one more old-fashioned disconnect method we hardly ever see anymore: a cord and plug to a wall receptacle within sight. When this method is used, protective conduit is not necessary. 

7) ATTIC WATER HEATER NOT READILY ACCESSIBLE - An attic water heater needs to be safely accessible for service. Getting to it should not involve stepping cautiously on the bottom chords of trusses and crawling over ducts. This means there should be a solid floor 24-inches wide running from the attic hatch opening for not more than 20-feet to a 30-inch by 30-inch level platform in front of the water heater. Also, an attic light and receptacle outlet is required near the water heater, with a switch located near the attic opening. 

8) INSTALLED IN PROHIBITED LOCATION - A gas water heater cannot be installed in a storage room, bedroom, bedroom closet, bathroom, or bathroom closet, to reduce the risk of carbon monoxide poisoning. An exception is allowed if the closet is a dedicated enclosure, with solid, weather-stripped and self-closing door, and an exterior source of combustion air.

9) NO CATCH PAN UNDER WATER HEATER - A watertight and corrosion-resistant pan is required under a water heater in an attic or where leakage would cause damage. A drain pipe from the pan must end near the ground at the exterior as indirect waste into the plumbing drain system. When the side of a catch pan gets cracked during installation or from storing heavy items on it, the pan is no longer functional as a leak protection device.

10) FLAMMABLES NEAR VENT - A minimum of 6-inches clearance from a single wall metal vent for a gas water heater to any flammable material, or minimum 1-inch for Type B double-wall.

   This list is just the basics. A gas water heater, for example, requires adequate combustion air, a properly aligned draft hood, and resolving conflict of any nearby air-exhaust appliances that may cause a backdraft from the draft hood—a few more of the  multiple other considerations for a good installation.

    Also see our blog posts Why is a leaning water heater a safety problem? and Is a catch pan and drain piping required for a replacement water heater?

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Here’s links to a collection of more blog posts about WATER HEATERS:

Are water heaters required to be raised off the floor? 

Can a Temperature and Pressure Relief (TPR or T&P) valve be mounted to discharge horizontally?

Where are gas water heaters not allowed to be installed?  

Is the minimum size water heater inlet pipe 1/2" or 3/4" according to the building code? 

Can you use a light switch for a water heater disconnect? 

How can I tell if a water heater is HUD-approved for mobile/manufactured homes?

Can you wire a 240-volt water heater with 120 volts? 

Is it alright to have a shut-off valve on both the hot and cold water pipes at a water heater?  

What is the minimum clearance to doors and windows for an outdoor tankless gas water heater? 

What is required clearance for access and working space in front of an electric water heater? 

Why is the water heater older than the house? 

Does a water heater need a shut-off valve? 

Why should a tankless water heater have an isolator/service valve kit installed?

When was a gas water heater first required to be elevated 18 inches above a garage floor?  

Can the temperature and pressure relief (TPR) valve discharge pipe for a mobile/manufactured home water heater terminate under the home? 

What is the purpose of a thermostatic mixing valve above a water heater? 

• What's the valve with the flip-up handle on the water heater for?

• Why is an older water heater an insurance problem?

    Visit our WATER HEATERS and COMMON PROBLEMS pages for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

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