Water Heater Replacement Plumbing Codes

Home » Water Heater Blog » Water Heater Replacement Plumbing Codes

Water Heater Replacement Plumbing Codes

We here at Water Heaters Only, Inc. always make sure we tell our customers that we do all of our jobs “up to code”, but we realize many people don’t always know what that means. The code we are referring to is the California Plumbing Code. If you have ever had to do any major renovation or repair on your home, you likely had to get a permit from the city and that meant you had to follow certain guidelines, or codes, for the work to be done. All incorporated cities have a building inspection and/or code compliance department. If they don’t, then that job will typically fall to the county. Either way, there are codes for just about every type of repair and renovation and that includes water heater plumbing codes.

According to the International Association of Plumbing and Mechanical Officials, the codes “attempt to minimize public risk by specifying technical standards of design, materials, workmanship and maintenance for plumbing systems.” Basically, these codes ensure that all repairs, replacements and installations are safe and effective, whether it’s installing a new bathroom or a water heater. Water Heaters Only makes sure that every one of our technicians are aware of all codes and any recent updates and we make sure to follow these codes as we have been doing now for over 50 years. For a full rundown of the required codes for water heater installations, visit our blog here.

Despite our knowledge of the plumbing codes, we realize that many people aren’t aware of them and so we thought it would be useful to go over some of the plumbing codes in the hopes of educating the public about how and why we go about performing our repairs and installations. However, before we go any further, it should be noted that each city and county can choose to implement these codes in different ways meaning that what is required in one city may not be required in another. It can get a little confusing, which is why it is so important to use a company that is up-to-date on all the latest codes.




While most of our California Plumbing Code (CPC) blogs will be about information in Chapter 5: Water Heaters (obviously), in this post we will be discussing water pressure and that is covered in Chapter 6, section 608. Just for starters, water pressure is measured in PSI, or pounds per square inch. Whenever we go out to any

job whether it is for a repair or an installation, we always check the PSI. This is useful because it can help determine the cause of a problem such as a leak or a water heater failure. According to CPC Section 608.2, whenever water pressure exceeds 80 PSI, a pressure regulator is required if there isn’t already one installed.

A pressure regulator does exactly what it sounds like: it regulates the water pressure in the plumbing. High water pressure can not only damage a home’s plumbing but can also damage a water heater as well. Most homes have one, but not always. If we find a home has water pressure above 80 PSI and there isn’t a pressure regulator, we will always offer to install one. And if there is one but the pressure is still high, we will check to see of the current one has failed. Not only can any water pressure above 80 PSI be detrimental to the water heater and plumbing, it will also void the warranty on most water heaters. For more information about water pressure and pressure regulators, please read our blog here.


Expansion tanks are an important part of minimizing damage to your water heater and plumbing and they are required in certain situations by the CPC. Basically, an expansion tank is a metal “bottle” that is used to relieve when thermal expansion occurs. The expansion tank had a bladder inside of it and when thermal expansion occurs, the expansion can be relieved temporarily by going into the tank. When the thermal expansion has stopped, the excess water goes back into the plumbing.

In the above section about pressure regulators, the CPC states that an expansion tank must be installed when a pressure regulator is installed. That’s because a pressure regulator causes the water to not be able to go back to the city main and is essentially locked into what is known as a “closed loop” plumbing system. It’s a closed loop because the water and thermal expansion, when it occurs, can’t go back to the city’s main water system located outside the home. In Section 608.3, the CPC also states that expansion tank must be installed if there is a check valve, backflow preventer or “other normally closed device that prevents dissipation of building pressure back into the water main”.


Section 608.3 also mentions the use of pressure relief valves in conjunction with expansion tanks. Not only must an expansion tank be installed when part of a “closed loop system”, there must also be a combination temperature and pressure (T&P) relief valve. For water heaters, these are typically located on the top of the water heater (though not always). Take a look at the picture above if you aren’t sure what the T&P looks like. These relief valves are set to relieve water and pressure after a certain PSI or temperature has been reached. These pressure relief valves need to also have a discharge pipe (Section 608.5), which has its own requirements such as:

  • The discharge pipe should discharge independently by gravity either into the drainage system or to the exterior of the building.
  • It must discharge in such a way that does not cause bodily harm or structural damage.
  • It cannot discharge into a water heater pan.

This is why you will typically see the T&P valve connected to a pipe that runs either alongside the wall to the outside or through the wall where it will be allowed to discharge in a safe place where no one may get hurt.

In conclusion, we hope this has been helpful information. One final note: As we mentioned in the beginning of this blog, each city may decide to implement the plumbing codes differently dependent on the situation. For example, in some areas the city inspector won’t require an expansion tank to be installed as long as there is a working T&P valve present. Also, an inspector may allow a T&P drain line to just discharge to the floor if the water heater is located in the garage. That’s why it’s so important to hire a company that knows the latest codes. For any further questions about water heater plumbing codes or to schedule an appointment with one of our water heater experts, just give us a call 24 hours a day, 7 days a week at 1-866-WHO-QUICK (1-866-946-7842).