Mixing Valves
Updated February 24, 2026
Blend hot and cold water to deliver a safe, consistent temperature. Thermostatic models automatically adjust to prevent scalding. Typical price range: $30 – $200. Best for: Shower valves, point-of-use water heaters.
Overview
Mixing valves blend hot and cold water to deliver a specific output temperature. Thermostatic mixing valves (TMVs) maintain a set temperature regardless of supply pressure changes. Anti-scald valves limit the maximum temperature to prevent burns. Installed at the water heater outlet (point-of-distribution) or at individual fixtures (point-of-use). Essential safety device in homes with children, elderly, or when the water heater is set above 120 degrees F for legionella prevention.
How to Choose Mixing Valves
Mixing Valves are best suited for shower valves, point-of-use water heaters. They typically cost $30 – $200, so plan your budget accordingly. Sizing is important — 3/4 inch for point-of-distribution (water heater outlet) serving the whole house. 1/2 inch for point-of-use at individua... Key advantages include scald prevention and consistent temperature.
Pros & Cons
- Scald prevention
- Consistent temperature
- Required by code in many areas
- Adds installation complexity
- Can fail and affect temperature
Key Features
- Blends hot and cold to deliver a preset, consistent output temperature
- Thermostatic element reacts automatically to supply temperature and pressure changes
- Anti-scald protection: limits maximum output to 120 degrees F (adjustable)
- Point-of-distribution (at water heater) or point-of-use (at fixture) installation
- Allows the water heater to run at higher temperatures (140 degrees F) for legionella kill while delivering safe 120 degrees F to fixtures
Top Brands for Mixing Valves
Sizing & Selection
3/4 inch for point-of-distribution (water heater outlet) serving the whole house. 1/2 inch for point-of-use at individual fixtures. Flow rate must match demand -- a whole-house TMV typically handles 5-15 GPM. Check the valve rating against your peak hot water demand.
Installation
Point-of-distribution: install on the hot water outlet of the water heater with a cold water bypass connection. The valve mixes cold water into the hot before it enters the distribution system. Point-of-use: install under the sink or behind the shower valve. Both require a cold water supply tee. Follow manufacturer instructions for temperature calibration.
Maintenance
- Test the output temperature annually with a thermometer at the nearest fixture.
- The thermostatic element can wear or scale over time, causing temperature drift. Recalibrate or replace every 5-10 years.
- Descale the valve in hard water areas -- mineral buildup affects the thermostatic element response time.
- If the output temperature suddenly spikes or drops, the thermostatic element may have failed. Replace immediately.
Buying Tips
- Honeywell, Watts, and Leonard are the main residential TMV brands.
- A point-of-distribution TMV (-150) is the most cost-effective way to protect the entire house.
- Setting the water heater to 140 degrees F with a TMV at 120 degrees F gives you legionella protection AND scald protection simultaneously.
- ASSE 1017 rated valves are certified for point-of-use anti-scald protection. Look for this certification.
- If you have a recirculation system, the TMV must be installed after the recirculation loop -- not in it.
Frequently Asked Questions
What are the advantages of mixing valves?
Scald prevention Consistent temperature Required by code in many areas
What are the disadvantages of mixing valves?
Adds installation complexity Can fail and affect temperature
Who should buy mixing valves?
Mixing Valves are best for: Shower valves, point-of-use water heaters.
How are mixing valves installed?
Point-of-distribution: install on the hot water outlet of the water heater with a cold water bypass connection. The valve mixes cold water into the hot before it enters the distribution system. Point-of-use: install under the sink or behind the shower valve. Both require a cold water supply tee. Follow manufacturer instructions for temperature calibration.
How do I choose the right size for mixing valves?
3/4 inch for point-of-distribution (water heater outlet) serving the whole house. 1/2 inch for point-of-use at individual fixtures. Flow rate must match demand -- a whole-house TMV typically handles 5-15 GPM. Check the valve rating against your peak hot water demand.
What are the best brands for mixing valves?
Top brands for mixing valves include Apollo, Bell & Gossett, BrassCraft, Caleffi. Each offers different price tiers and product lines.
How do I maintain mixing valves?
Key maintenance tips: Test the output temperature annually with a thermometer at the nearest fixture.. The thermostatic element can wear or scale over time, causing temperature drift. Recalibrate or replace every 5-10 years.. Descale the valve in hard water areas -- mineral buildup affects the thermostatic element response time..