Yes, the building code requires “hot” to be on the left as you face the water outlet (spigot) (IRC 2722.2). This means that if a faucet is on the side of a bathtub, like in the photo below, the hot water valve must be on the left when viewed from inside the tub, but would be on the right if approached from outside the tub.


    The purpose of this left-side requirement is to avoid accidental scalding by turning on the wrong faucet. Although it is recommended that water heater thermostats be set at 120º F to avoid a skin burn from a stream of exclusively hot water, many homes have the temperature set higher, so scalding by turning on the wrong faucet is a real possibility. Verifying that the hot water service is on the left is one of the things checked during a home inspection, and occasionally find the hot/cold reversed.

    Scalding prevention in a shower is addressed by a building code requirement for a single-handle anti-scald valve that prevents the water temperature from rising above 120º F. See our blog post Why are shower water valves all single-handle nowadays? to learn more.

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Here’s links to a collection of our other blog posts about PLUMBING:

• How can I protect my pipes to keep them from bursting during a hard winter freeze in North Florida?

• Why is the vacuum breaker at my hose faucet leaking, gushing water, or making funny sounds?

• Why is the cover plate of some water meter boxes in the ground painted purple?

• Why is it a problem when a trap under a sink is installed backwards? 

• What are the code requirements for plumbing vent terminations?

• What are the code requirements for layout of drain piping under sinks?

• Why is there sand in the bottom of my toilet tank?  

• What causes a gurgling sound when a bathtub or sink drains? 

• Are drop-in toilet bowl cleaner tablets safe?

• What can I add to my septic tank to help it work better? 

• Why do septic tank contractors want you to get rid of your kitchen disposal?

• Why is there mold inside my toilet tank?  

• What are the pros and cons of a wall-mounted toilet?

• Does a refrigerator water supply line require a shutoff valve behind it?

• Which plumbing fixtures require water shut off valves in a home? 

• Is a hot water faucet required at a washing machine?

• What are the pipes sticking out near my water valves?

• Can PEX pipe be installed outside?  

• What is the difference between water pipe and sewage (waste) pipe? 

• How can I tell if a house is connected to a septic tank system or sewer?

• Are plastic pipes (PVC, CPVC, and PEX) safe for drinking water? 

• What do the ABS, PVC, CPVC, PB, and PEX plumbing pipe names mean?

• Why is a backflow preventer required on lawn sprinkler systems? 

• How can I locate my septic tank?

• Can you live in a house while the plumbing is being replaced?

• What is the loose wire sticking out of the ground under the gas meter for? 

• Why is sunlight exposure bad for PVC pipe?

• Why is the European-style bottle trap not approved by the plumbing codes in the U.S.? 

• Does a home inspector check the plumbing under the floor slab?

• Is it alright to disconnect the washing machine drain from the septic tank and divert it to the ground in the yard?

    Visit our PLUMBING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.