The Uniform Plumbing Code and International Building Code, in accordance with ASSE 1016, require that all tub/shower faucets now be of the pressure balance or the thermostatic mixing valve type. Two and three valve handles are not. The purpose for this is to prevent serious harm from hot water scalding.
The exact text from the Uniform Plumbing Code book, ISSN 0733-2335, states in section 420.0 €“ SHOWER
AND TUB/SHOWER COMBINATION CONTROL VALVES:
€śShowers and tub/shower combinations in all buildings shall be provided with individual control valves of the pressure balance or the thermostatic mixing valve type. Gang showers, when supplied with a single temperature controlled water supply pipe, may be controlled by a master thermostatic mixing valve in lieu of individually controlled pressure balance or thermostatic mixing valves.€ť (pg. 30-31).
So what does this all mean to you? Well, if you have a 2 or 3 handle tub/shower valve currently in your home, you have been grandfathered in and you dont need to immediately replace it. However, if something goes wrong with that valve and it must be replaced, you will have to do so with a single handle pressure balanced or thermostatically controlled valve.
While you can still purchase these two or three handle faucets online and from some suppliers and install them yourself, or have a non licensed plumbing professional install them, we wouldnt recommend this. This devalues your home and puts your family at risk of severe water scalding. Let a licensed professional do the necessary work to make sure your home is repaired to code and under a solid warranty.
--
For full context, visit
https://www.homeownershub.com/mainte...al-329902-.htm