Water heaters play a crucial role in providing hot water for household needs. They are connected to a complex network of pipes that supply water to and from the water heater unit. Knowing what these pipes are and what they do is important for proper water heater installation and maintenance.
There are five main pipes connected to a water heater:
- Cold water inlet pipe – Supplies cold water to the water heater.
- Hot water outlet pipe – Takes heated water from the water heater to hot water fixtures.
- Temperature and pressure (T&P) relief valve pipe – Safety valve that opens to release excess heat and pressure.
- Drain pipe – To drain and flush the water heater tank.
- Gas supply pipe – Supplies gas to a gas water heater.
Understanding the function of each of these water heater pipes is important. We’ll provide an in-depth look at what each pipe does and how they need to be installed.
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Cold Water Inlet Pipe
The cold water inlet pipe, also known as the cold water supply line, is the main water supply line that feeds water into the water heater. This pipe is connected from the main home water supply lines to the cold water inlet on the water heater.
The size of the cold water inlet pipe should match the water heater’s inlet connection size, usually 3/4 inch or 1/2 inch NPT (National Pipe Thread). Copper is the most common material used for the cold inlet water line. Make sure the pipe is fully inserted into the water heater’s inlet fitting and a pipe thread sealant is used to prevent leaks.
The water flow into the system needs to be adequate to supply the heating demand. Most residential water heaters require a minimum water flow rate of .5 gallons per minute or more. The cold water supply line should have a full-bore ball valve installed to allow the water supply to be shut off for service.
It’s also advisable to have a union fitting connecting the water lines to the water heater so it can be easily disconnected for maintenance. Properly installing the cold water inlet pipe is crucial to ensure efficient operation and prevent premature failure.
Key Facts on Cold Water Inlet Pipes
- Connects from main home water lines to water heater
- Usually 3/4″ or 1/2″ NPT thread
- Must match water heater inlet size
- Copper pipe is standard
- Requires full-bore shutoff valve
- Union fitting allows easy disconnect
Hot Water Outlet Pipe
The hot water outlet pipe transports heated water from the water heater to distribution points. When the water in the tank reaches the desired temperature, the thermostat triggers the water heater to stop heating. The buoyancy of the hot water causes it to rise to the top of the tank where the outlet pipe is located.
The hot water outlet pipe is then responsible for delivering the heated water from the tank to fixtures throughout the house needing hot water. This includes faucets, showers, appliances, etc.
Proper installation of the hot water outlet line includes:
- Must match the water heater’s hot water outlet diameter, usually 3/4″ or 1/2″ NPT thread
- Attaching the outlet piping into the hot water outlet fitting using thread sealant
- Ensuring the pipe is adequately supported
- Insulating the hot water lines to minimize heat loss
Using copper and avoiding excessive bends are also important. The hot water line should take the most direct path to fixtures to deliver hot water quickly. Just like the cold inlet, the hot water outlet line should have a full-bore ball valve installed to allow easy isolation if maintenance is needed.
Key Facts on Hot Water Outlet Pipes
- Transports hot water from heater to fixtures
- Connects to hot water outlet on top of tank
- Must match water heater outlet size
- Should be copper and well insulated
- Needs full-bore shutoff valve
T&P Relief Valve Pipe
The temperature and pressure (T&P) relief valve is one of the most important safety components on a water heater. All water heaters are required to have a T&P relief valve installed on the tank.
This valve serves as a backup safety precaution to release excess pressure or heat if the tank exceeds safe temperature/pressure limits. The T&P valve is normally closed, but will automatically open if the water temperature goes above 210°F or the pressure exceeds 150 psi.
When opened, the T&P valve discharges the overheated water or pressure through a discharge pipe attached to the valve outlet. This T&P discharge pipe must meet the following requirements:
- Must be at least 3/4″ diameter pipe
- Should be metal or CPVC (not regular PVC which can melt)
- Pipe must be sloped constantly downward to allow drainage
- Discharge point must be 6-12 inches above a drainage point
- Discharge pipe should be as short as possible and have no more than 4 elbows
- The end should be non-threaded to allow free flow if opened
The discharge point should release onto the floor near a drain or outside the building. This ensures dangerous steam and hot water is safely discharged. Proper installation of the T&P valve discharge pipe is critical for the safe operation of the hot water system.
Key Facts on T&P Relief Valve Pipes
- Safety valve that releases excess heat or pressure
- Pipe must be 3/4″ diameter minimum
- Sloped constantly down to drain point
- Discharge point 6-12″ above drain
- Pipe should be short with minimal elbows
Drain Pipe
Every water heater has a drain valve at the bottom of the tank. The drain pipe threads into the drain valve and allows the tank to be drained fully.
Draining the water heater is necessary for flushing out sediment, making repairs, or draining the tank for winterization to prevent freezing damage. The drain pipe assembly is commonly composed of the following:
- Drain valve – Usually a 3/4″ hose bibb, ball valve, or gate valve.
- Drain pipe – Short length of 3/4″ pipe threaded into drain valve.
- Garden hose adapter – Allows connecting a garden hose for drainage.
When draining the tank, the drain hose should extend to an adequate drain point like a floor drain, sump pit, outside area, or buckets. The drain pipe helps get hot water safely away from the water heater vicinity.
Some tips for proper drain pipe installation include:
– Use Teflon tape on valve threads
– Hand tighten well to prevent leakage
– Position valve close enough to floor to allow hose attachment
– Ensure valve works properly by testing
The drain pipe assembly provides an efficient way to flush and drain the water heater when needed for maintenance.
Key Facts on Drain Pipes
- Threads into drain valve on bottom of tank
- Usually 3/4″ pipe with hose adapter
- Allows tank draining for maintenance
- Drain hose sends water to safe location
- Valve should be near floor and testable
Gas Supply Pipe for Gas Water Heaters
For gas water heaters, an additional pipe needs to be connected – the gas supply line. This pipe supplies natural gas or propane to the water heater burner and combustion chamber where it’s ignited by the pilot light.
Proper gas line installation is extremely important for safe operation of a gas water heater. Gas supply pipes must meet the following criteria:
- Right size to provide adequate gas volume to the water heater
- Approved pipe material – copper, black iron, CSST, etc.
- Adequately secured
- Properly sealed connections
- Shutoff valve installed to isolate gas supply
- Sediment trap installed per code
- Appropriate leak testing performed
In addition, the gas pipe sizing must account for the BTU rating of the water heater and length of the supply run. Usually a 1/2″ or 3/4″ pipe is sufficient for most residential heaters.
The key is properly sizing, routing, securing, and testing the gas supply piping according to fuel gas codes. This ensures adequate gas flow and prevents dangerous leaks.
Key Facts on Gas Supply Pipes
- Provides gas to burner for combustion
- Must be properly sized for BTU load
- Approved materials like steel or copper
- Sealed and secured connections
- Shutoff valve for isolation
- Sediment trap installed per code
Conclusion
In summary, water heaters require proper connection of several key pipes for safe operation:
- Cold water inlet pipe
- Hot water outlet pipe
- T&P relief valve discharge pipe
- Drain pipe
- Gas supply pipe (for gas heaters)
Each pipe has specific installation and sizing requirements. Connecting the pipes according to manufacturer specifications and fuel gas code provides the safe delivery of water and gas to the water heater. Proper pipe connections are crucial to water heater functionality and safety.