What is a Boiler Drain Valve?
Boiler drain valves are manually-operated valves that drain water and eliminate sediment from boilers in steam heating systems to maximize system efficiency. They also provide a hose end connection for external water service. Draining water and sediment from boilers is essential maintenance.
How to Fix a Leaking Boiler Drain Valve
Reasons Boiler Drain Valves Leak
- High Boiler Pressure – If there is excessive water discharge, the boiler’s pressure may be too high. Check the pressure gauge to see if the pressure is too high. If this is the case, the pressure relief valve is likely trying to release some of the water in the system to bring the pressure back down to a comfortable level, which can lead to the boiler dripping water.
- Cracked Boiler System – Any metal object that comes into continuous contact with water eventually develops stress and strain, especially under heavy usage conditions. Over time, cracks may appear in the boiler’s metal due to the expansion and contraction. Wear and tear may also be seen in the copper lines and valves that enter and exit the boiler after prolonged use.
- Loose or Damaged Sealing Connection – The expansion and contraction brought on by the heating and cooling of a boiler affect not only the boiler but also the seals and valves that join the tubes to the heater and radiator systems. Over time, connections between a valve and a boiler may become loose and cause leaks. Additionally, broken valves or seals can cause boiler leaks. The integrity of the seals and valves can be compromised and damaged by hot water flowing through the pipes.
- Dirt or Sediment Buildup – Debris accumulation at the boiler’s valve can cause the drain valve to leak. The valve becomes weaker due to the accumulation of debris. Regular maintenance can help alleviate buildup issues.
- System Corrosion – Corrosion can cause rust and other debris to build up within radiators and pipes. As the water runs around the system, it can pick up this debris and return it to the boiler. The older the system, the more likely it is to have corrosion issues, leading to the boiler leaking water from the bottom. Corrosion can also break the rubber seals around the joints of pipes.
- Faulty Heat Exchanger – The heat exchanger allows a boiler to heat cold water, which is an essential part of the appliance. A leaking boiler can signal that the heat exchanger is starting to decay. It’s not uncommon for this part to crack over time.
Fixing or Replacing a Leaking Boiler Drain Valve
Step 1 - Bleed the Radiator Valves
The boiler feeds steam to the radiators, which must be drained and bled before repairing or replacing a leaking boiler valve. With the heating system engaged and working, go to each radiator throughout the building and use the valve key to open the valves. When opened, the valves should make a hissing sound, and water may spit out during this process. Use towels and place them underneath the bleeding valve. Make sure not to put a hand over the hissing steam as it could cause burns.
Step 2 - Drain the Boiler
Open up the boiler valve and allow all the water inside to drain. Again, place towels underneath the valve to contain any spillage that will seep out of the boiler. Look at the discharge when the boiler is drained to determine whether rust is present. The color of the discharge will be brown.
Step 3 - Add a Rust Inhibitor
Spray the boiler valve with rust inhibitor. Rust may have caused the leak, and spraying rust inhibitor will help seal the valve and make it work properly again.
Step 4 - Refill the Boiler
Use a garden hose to refill the boiler with water. Only fill the boiler to its recommended water level. Once refilled, close the boiler valve and watch it for several minutes. Then, check to see if any water is leaking out. If the leak has stopped, you can proceed to the final step. If not, repeat steps 1 and 2 and replace the boiler drain valve.
Step 5 - Close the Radiator Valves
If the boiler valve leak is sealed and the boiler works again, return to your building’s radiators and close up the valves.
Boiler Drain Valve FAQs
Where is the drain valve on a boiler?
Typically, a drain valve is located near the base of the boiler, almost always at the boiler’s lowest point. Look for a valve screwed onto a short, threaded pipe protruding from the boiler. It will likely be the only one protruding from the boiler that does not connect to another pipe. On the outer end of the drain valve, you’ll see a spigot similar to a faucet.
How do I prevent galvanic corrosion in boiler drain valves?
Galvanic corrosion is one of the most common types of corrosion. Some methods to prevent galvanic corrosion include replacing the ground wire connection to the water line with a grounding rod, using dielectric couplings, and wrapping water lines in plastic.
What is the difference between a boiler drain valve and a hose bibb?
Hose bibbs help control water supply flow, while boiler drain valves drain water and sediment securely. Hose bibbs also feature an extended garden hose thread.
NIBCO Boiler Drain Valves
NIBCO Figure No. 74-CL Valves
This multi-turn boiler drain, with copper- or male-threads-to-hose connections, ensures trouble-free operation and easy access. This multi-purpose drain valve is recommended for use in low-pressure water systems.
- Valve pressure rating 125 psi to 100°F
- Maximum temperature 180°F/82.2°C
- Screw-in bonnet
- Buna-N seat
- 1/2" cup or MIP to hose connections
- 3/4" MIP to hose connections
- Dezincification resistant
- Use in U.S. drinking water applications is prohibited after January 3, 2014
NIBCO Figure 72 Boiler Drain Valves
This multi-turn boiler drain, with cup-to-hose connections, ensures trouble-free operation and ease of access.
- Valve pressure rating 125 psi to 100°F
- Maximum temperature 180°F/82.2°C
- Buna-N seat
- Cup-to-hose connections
- Dezincification resistant
- Use in U.S. drinking water applications is prohibited after January 3, 2014
NIBCO Figure 73-CL Boiler Drain Valves
This multi-turn boiler drain, with FIP-to-hose connections, is recommended for use in low-pressure water systems.
- Valve pressure rating 125 psi to 100°F
- Maximum temperature 180°F/82.2°C
- Screw-in bonnet
- Buna-N seat
- Threaded to hose end connections
- Dezincification resistant
- Use in U.S. drinking water applications is prohibited after January 3, 2014
NIBCO Figure 74-2 Boiler Drain Valves
This multi-turn boiler drain, with fitting-to-hose connections, ensures trouble-free operation and easy access. This multi-purpose drain valve is recommended for use in low-pressure water systems.
- Valve pressure rating 125 psi to 100°F
- Maximum temperature 180°F/82.2°C
- Screw-in bonnet
- Buna-N seat
- Fitting to hose end connections
- Dezincification resistant
- Use in U.S. drinking water applications is prohibited after January 3, 2014
NIBCO Figure QT74X Boiler Drain Valves
This quarter-turn boiler drain, with FIP-to-hose connections, ensures trouble-free operation and ease of access and is for use in low-pressure water systems.
- Valve pressure rating 125 psi to 100°F
- PTFE Seat
- Maximum temperature 180°F/82.2°C
- Cup or MIP threads to hose connections
- Use in U.S. drinking water applications is prohibited after January 3, 2014
NIBCO Figure QT73X Boiler Drain Valves
This quarter-turn boiler drain, with cup- or MIP-to-hose connections, is manufactured from brass, with a PTFE seat and nitrile O-ring, and is recommended for use in low-pressure water systems.
- Valve pressure rating 125 psi to 100°F
- PTFE Seat
- Maximum temperature 180°F/82.2°C
- FIP to hose connections
- Use in U.S. drinking water applications is prohibited after January 3, 2014
NIBCO Figure 4464 Boiler Drain Valves
This transition boiler drain, with compression-to-hose connections, is recommended for use in low-pressure water systems.
- Valve pressure rating 125 psi to 100°F
- Maximum temperature 180°F/82.2°C
- Screw-in bonnet
- Buna-N seat
- Compression x hose connections
- Dezincification resistant
- Use in U.S. drinking water applications is prohibited after January 3, 2014
- IAPMO Listed to cUPC
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Webstone Boiler Drain Valves
The Webstone Pro‑Pal series is a line of step-saving valves designed to anticipate the future needs of the systems or appliances they support, with built-in valves and drains for simplified isolation and service. The Pro-Pal series also features forged brass alternatives that replace common assemblies made in standard installations, resulting in a cleaner-looking installation with fewer components and leak paths. In addition, Webstone’s extensive offering includes a variety of exclusive designs, including products with functions that cannot be achieved using off-the-shelf components. Pro-Pal products are designed for water, oil, or glycol mix use in residential or commercial plumbing and heating systems.
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Webstone Pro-Pal Ball Drain Solutions
Pro-Pal ball drains feature multi-function and adjustable stem options that allow draining from either side of the ball. The ball drain saves 25 minutes of installation time and eliminates three leak paths, while the ball drain strainer saves an hour and seven leak paths. In addition, these valves eliminate assemblies needed to isolate and drain any portion of a piped system.
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Shop Webstone Pro-Pal Ball Drain Valves with Union
Shop Webstone Pro-Pal Ball Drain Valves with Transition
Shop Webstone Pro-Pal Ball Drain Strainer Valves
Shop Webstone Pro-Pal PP-RCT Ball Drain Valves
Webstone Pro-Pal T-Drains
Pro-Pal T-drains eliminate assemblies needed to install drains/draw-offs into a line. They easily install anywhere a drain or purge valve is required.
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Webstone Pro-Pal Add-a-Drain
Add-a-Drains are a full-port, quarter-turn alternative to traditional boiler drains. Their straight design allows for more convenient service access, while the compact handle saves space. The lead-free forged DZR brass construction is suitable for hydronic or potable applications. Connections up to 1-1/2" cover a broad range of applications. This valve is actuated by a blowout-proof stem and features an adjustable packing gland. They are available in MIP x Hose, FIP x Hose, SWT x Hose, PRS x Hose, & GMT x Hose connections.