A shut-off valve is required on the cold water supply pipe to water heater. Here’s how the Residential Edition of the Florida Building Code (FBC) and the International Residential Code (IRC) state it:

    A “full-open” valve is one that does not restrict the flow of water when open all the way. A ball valve, like the one shown above, which utilizes a center ball with a round tunnel cut out of its center, and a gate valve, which uses a plate that descends across the pipe cross-section to close it, are two types of full-open valves.

    A globe valve, shown in the diagram and photo below, reduces water flow because the water has to zig-zag around a perpendicular opening smaller than the cross-section of the pipe. The globe valve’s advantage is that it can adjust water flow; but that is not something you want to do at a water heater, because the reduced flow can reduce pressure downstream at the fixtures it serves.

    Although gate and globe valves look similar, there are two ways you can tell which one you are looking at:

1. When viewed from the side, a gate valve has a taller face below the stem.
2. The handle will rise much higher, with a long stem exposed, when a gate valve is in the open position.

    A valve is necessary to stop the water flow if the tank is leaking or requires repair, without having to lose water service to the entire home, and also when flushing the tank to get rid of sediment accumulation in the bottom.

    Sometimes we see shut-off valves at both the hot and cold pipes near the water heater. There is nothing wrong with it, but the second shut-off at the hot water side is not necessary—except as part of a flush kit for a tankless (on-demand) water heat. What we don’t want to see is no shut-off valve at all, like at the water heater shown below. It gets written up as a defect in the home inspection report.

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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? 

• 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? 

• Does a tankless gas water heater still work with no electricity during a power outage?  

•  Why do water heaters have a sacrificial anode? 

• What is the difference between a manufactured/mobile home water heater and a regular water heater? 

• Does a tankless water heater require a pressure relief valve?

• When is a water heater drain pan required?

• Why is there water in my water heater drain pan?

• What does it mean when a water heater Temperature/Pressure Relief (TPR) discharge pipe is "trapped"? 

• Can I leave a gas water heater in place when remodeling a garage into a family room or bedroom? 

• Where do I find the water heater in a mobile home?

• Does a tankless water heater in an attic require a drain pan? 

• Does an electric water heater require a disconnect? 

• Is a catch pan and drain piping required for a replacement water heater?

• What is the difference between a single element and dual element electric water heater? 

• What is an FVIR water heater?

• What is a heat pump water heater?

• What is a dielectric union?

• What's that powdery crust on the pipe connections at the water heater? 

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

• Why is my water heater making strange (rumbling, gurgling, knocking or banging) noises? 

• What can I do to make my water heater last longer?

• How can I determine the age of a water heater if the serial number is missing or decoding it is impossible? 

• How does a hydronic heating system work?

• What is the difference between a regular water heater and a direct vent water heater? 

• What is the difference between a regular water heater and a power vent water heater?

• What is backdrafting at a gas water heater? 

• How do I determine if a water heater is gas or electric?

• What does it mean when a gas appliance (water heater, furnace, or range) has been "red tagged"?  

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