How Safety Relief Valves Function in Hot Water Systems

How do safety relief valves work

Safety relief valves are crucial components in hot water systems, regulating temperature and pressure to prevent potential damage.

These valves are designed to expel water when temperature or pressure in the tank reaches hazardous levels, typically above 99°C or the water heater’s maximum capacity.

There are two common types of relief valves:

• Temperature Relief Valve (TRV) - releases water to lower temperature if it surpasses a predetermined point, typically near 99°C.
• Pressure Relief Valve (PRV) - activates to release water and alleviate pressure if it exceeds 1000 kPa or the system’s specified limit.

Upon activation, the valve discharges hot water through an external drain line, preventing further pressure build-up and mitigating excessive heat within the system.

It’s crucial for homeowners to test these valves regularly by operating the handle, ensuring they function correctly and are free from obstructions. Faulty relief valves are dangerous - if unable to open when required, pressure can continue rising until the tank explodes.

Conducting a monthly inspection is advised.

Types of safety relief valves

There are three main types of safety relief valves used in hot water systems:

1. Temperature and Pressure Relief (TPR) valve - Designed to open and discharge water if either the temperature or pressure exceeds safe thresholds in the system. This is the most common type installed in domestic and commercial water heaters.
2. Temperature-only relief valve - Activates solely based on high temperature rather than pressure buildup. Used only in open systems where pressure can’t accumulate.
3. Pressure-only relief valve - Opens strictly based on excessive pressure in the system. Useful for equipment sensitive to temperature change but still at risk of pressure overload.

Selecting the right valve relies on the specific water heater, systemic risks, and local plumbing codes and standards. A licenced plumber can advise on selecting and installing suitable, compliant relief valves when installing or replacing your hot water system.

Regardless of type, ensure valves have proper discharge lines to route released water safely away from the equipment and your home.

How to test a safety relief valve

It is essential to test your heater pressure relief valve monthly to confirm it can adequately release excess pressure or temperature. Follow these steps monthly:

1. Turn off power to the water heater at the circuit breaker.
2. Position a bucket beneath the relief valve drain line to collect any discharged water, ensuring it’s outside the house.
3. For pressure relief valves, gently elevate the lever. You should hear a release of pressure and some water may drain into the bucket.
4. For a temperature relief valve, hold the lever fully open for 30 seconds. Hot water will discharge from the drain line into the bucket.
5. Release the lever and ensure it closes properly to stop water flow.
6. Check the valve and related pipes for any blockages, corrosion or damage. Make any necessary repairs.
7. Replace the valve if it isn’t working correctly based on age or condition.
8. Turn circuit breaker back on once testing is complete.

Monthly tests ensure relief valves can safely vent excess pressure or heat, crucial for maintaining safe system operation. If a valve fails to open and discharge water correctly during testing, have it replaced promptly by a professional.

Manual testing

In addition to monthly inspections, perform a thorough manual test of the hot water system’s safety relief valves every 6 months for routine maintenance.

To perform a comprehensive manual test:

1. Ensure all power to the water heater is switched off.
2. Close the cold water supply valve that feeds your water system to the water tank.
3. Open a hot water tap inside your building to release pressure in the plumbing system.
4. Place a bucket underneath the relief valve drain line exit point.
5. Lift the relief valve lever completely for approximately 30 seconds. This rapidly releases tank pressure.
6. Check the valve and related pipes for any leaks, corrosion or damage. Make repairs as needed.
7. Allow the tank to completely cool then reopen the water supply valve.
8. Turn power back on to the water heater.
9. If issues persist despite testing and servicing, a replacement of the relief valve may be required.

Manual testing provides an exhaustive evaluation of safety relief valve functionality. Conducting this test every six months bolsters confidence in your system’s capacity to manage extreme pressure and temperature.

Safety precautions

1. Always turn off the water heater’s power at the circuit breaker before any valve tests.
2. Use a bucket to catch any hot water released while testing to avoid scalds.
3. Wear protective gloves when inspecting fittings and pipes for leaks or damage.
4. Route the drain line safely away from areas where released water could cause property damage.
5. If released water comes into contact with electrical equipment, turn off power before accessing.
6. Replace faulty or ageing valves to maintain reliability.
7. Keep the valve inspection port clear of obstructions.
8. Never plug or cap the relief valve or drain line.
9. Call a plumber immediately if the relief valve fails to operate properly.

Signs of a faulty relief valve

There are several key signs that may indicate your hot water system’s safety relief valve is faulty or failing:

• Abnormal noises - Hissing, rumbling or popping sounds can signify steam and pressure escaping a stuck valve.
• Leaks - Water seeping from the valve or related piping when the system is idle.
• Failure to release pressure - Inability to discharge water properly when manually tested.
• Damaged components - Corroded, bent or cracked fittings, pipes or valve body.
• Age - Relief valves deteriorate over time. If your valve is over 5 years old, have it replaced as routine maintenance.

A faulty relief valve unable to open poses a serious safety hazard. Contact a licenced plumber immediately if you notice any of the above signs to avoid potential water heater explosions or other catastrophic failure.

As part of repairing the valve, they will check the entire hot water system for proper temperature and pressure thresholds. Pressure relief valves may need replacement if sticking or damaged to maintain reliable protection.

Replacing a faulty relief valve

Replacing a defective or outdated relief valve is essential for maintaining the safety and integrity of your hot water system.

1. DIY - Homeowners can attempt to replace relief valves themselves provided they have plumbing experience and can fully isolate the water heater. Make sure you match specifications of the new valve to your existing water heater.
2. Professional replacement - For many homeowners, engaging a licenced plumber is the optimal choice for replacing a faulty relief valve. At Seven Hills Plumbing, our skilled team can identify and install the perfect relief valve for your system, ensuring safe replacement and managing any potential leaks or pressure issues.

Our process for replacing relief valves involves:

• Isolating water supply lines and turning off power to the water heater
• Draining excess pressure from the tank and attached plumbing
• Removing the faulty valve and sealing fittings
• Installing the new relief valve with compatible specifications
• Attaching discharge pipes directed safely away from the home
• Testing the new valve to validate proper operation
• Flushing the system and refilling the tank
• Restoring water supply and power to the water heater

With a new, functioning relief valve installed, your hot water system regains its crucial protective failsafe against excessive pressure and temperature. Contact our team at Seven Hills Plumbing on 1300 349 338 or [email protected] to schedule relief valve replacement.

DIY replacement

Homeowners can replace relief valves themselves if confident working with plumbing and electrical systems. However, due to safety risks, we recommend contacting a professional plumber.

If attempting DIY replacement, ensure you have the necessary skills, proper tools and equipment including:

• Adjustable wrench
• Pipe wrench
• Bucket
• Torch
• Replacement relief valve to suit your existing hot water system
• Protective equipment - gloves, goggles, non-slip shoes

Key steps involve:

1. Disconnect both power and water supply to the hot water system
2. Release pressure from the tank and piping
3. Remove old relief valve using wrenches
4. Clean fittings thoroughly and check for damage
5. Install new relief valve as per manufacturer instructions
6. Attach discharge pipe to a safe drainage exit point
7. Restore water and power to the system
8. Test new valve opens correctly when lever is lifted/turned

Adhere to all relevant plumbing regulations and codes. Never compromise safety. Call a licenced professional if you have any concerns replacing relief valves DIY-style.

Hiring a professional

With safety relief valves being essential protective components in hot water systems, having faulty or dated valves replaced is critical. However, replacement involves working with complex plumbing and electrical equipment that poses risks if not addressed properly.

Engaging with professional plumbers such as Seven Hills Plumbing for valve replacement offers key advantages like:

• Expertise and compliance - Our licenced, fully insured technicians have extensive training and experience replacing all relief valve types according to plumbing codes and standards.
• Safety - We isolate water heaters, release pressure appropriately, and handle hazardous discharges safely with proper equipment.
• Warranty on parts/labour - Our valve replacements include a 1-year warranty on components and workmanship for peace of mind.
• Proper disposal - We correctly dispose of old valves and parts rather than leaving hazardous materials onsite.
• System validation - Our specialists check your entire system’s temperature/pressure levels and make any adjustments required to ensure peak safety.

Don’t compromise safety or reliability - allow our experts at Seven Hills Plumbing to replace your relief valves. Contact us on 1300 349 338 or email [email protected] to schedule your appointment.