Basement Water Heater Temperature & Pressure Valve Discharge Pipe to the Outdoors

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How to install basement water heater Temperature & Pressure valve discharge pipe to the outdoors to comply with the Plumbing Code. I hired a plumber to replace the old heater and route the new T&P discharge line upward to the outdoors to prevent flooding.

Table of Contents

  1. Gas Water Heater Replacement Cost and Code Compliance
  2. Natural Gas Hot Water Heater Replacement Process
  3. How to Install a FloodStop Water Heater Auto-Shutoff Valve
  4. Water Heater Replacement – Gas Supply & Type B Flue Vent Connections
  5. Basement Water Heater Temperature & Pressure Valve Discharge Pipe to the Outdoors (you are here)

Old Water Heater – Improper T&P Discharge Pipe

The old heater Temperature & Pressure (T&P) relief valve discharge pipe will dump water on the basement floor. If the valve is corroded and sticks open the basement will flood because cold water will flow into the tank and out the discharge line until the water supply is shutoff. If I’m away from home, the basement could be flooded with thousands of gallons of water!

Natural Gas Water Heater in Basement - Temperature & Pressure Valve Discharge Pipe Code Violation

Natural Gas Water Heater in Basement – Temperature & Pressure Valve Discharge Pipe Code Violation

Plumbing Code Requirements for Water Heater T&P Discharge Piping

2012 International Plumbing Code in Chapter 5 Water Heaters, Section 504.6 “Requirements for discharge piping” says in laymen’s terms that the piping:

  • Cannot be directly connected to the sewer line.
  • Shall discharge to the floor, water heater drain pan or storage tank, to a floor drain or the outdoors.
  • Discharge such that it doesn’t cause structural damage or personal injury.
  • Discharge to a readily noticeable location.
  • Be installed to flow by gravity (i.e. downhill sloping pipe).

The challenges to meet the requirements of Sec. 504.6 for a basement water heater are:

  • Installing a floor drain be expensive.
    A channel would have to be cut in the concrete floor to install a drain, piping and a high-capacity sump pump.
  • An outdoor gravity-flow drain line also requires cutting a long deep channel in the slab for a drain and piping.
  • The new water heater has a 24″ drain aluminum drain pan that can hold at most 6 gallons.
    The drain pan is only sufficient for minor T&P valve releases.

It seems there is no reasonable solution.

Basement Water Heater Temperature & Pressure Valve Discharge Pipe to the Outdoors

Fortunately I live in the State of Georgia which allows upward discharge piping! The Georgia State Amendments to the 2012 International Plumbing Code (revised January 1, 2014) states in Chapter 5 Water Heaters, Section 504.6 “Requirements for discharge piping.” states (emphasis added):

“The relief valve shall discharge full size, separately to a safe place of disposal such as a concrete floor, outside the building, an indirect waste receptor, pan, or other approved location. The discharge shall terminate in a manner that does not cause injury to occupants in the immediate area or structural damage to the building. When the relief valve discharge piping goes upward, a thermal expansion control device shall be installed on the cold water distribution or service pipe in accordance with Section 607.3.2. If the discharge pipe is trapped, provisions shall be made to drain the low point of the trapped portion of the discharge pipe.
(Effective January 1, 2014)”

The upward discharge pipe solution is:

  1. Install a thermal expansion tank.
  2. Route the CPVC discharge pipe upward to the 1st floor joists and outdoors by the front porch for safe disposal where it’s readily noticeable.
  3. Install a drain valve at the lowest point in the line.

It’s easy to comply with the State of Georgia requirements per the following photos:

  • The thermal expansion tank is the small tank above the water heater.
  • The CPVC discharge line runs up to the 1st floor joists and outside by the front porch.
  • A drain valve is installed at the lowest point below the 90 degree elbow.
Basement Water Heater Temperature & Pressure Relief Valve - Upward Discharge Piping

Basement Water Heater Temperature & Pressure Relief Valve – Upward Discharge Piping

The water heater T&P valve points down as installed at the factory. The plumber turned the valve horizontally to connect the 3/4 inch copper pipe and 1/4 turn drain valve:

Basement Hot Water Heater Temperature & Pressure Relief Valve - Drain and Upward Piping

Basement Hot Water Heater Temperature & Pressure Relief Valve – Drain and Upward Piping

3/4 inch CPVC discharge pipe runs under the 1st floor joists and across my workshop to clear the front porch. The discharge pipe is supported by pipe hangers nailed to the joists. I have a deep daylight basement because the house is on a hillside:

Basement Hot Water Heater Temperature & Pressure Discharge Line Routed to Outdoors

Basement Hot Water Heater Temperature & Pressure Discharge Line Routed to Outdoors

The water hose bib was referenced to determine where to drill a hole in the outside wall for the T&P discharge pipe. The pipe will dump water safely on the ground:

Basement Water Heater Temperature & Pressure Discharge Line to Outdoors

Basement Water Heater Temperature & Pressure Discharge Line to Outdoors

My home is now much more resistant to water heater leaks and flooding with the outdoor T&P discharge pipe and the FloodSafe auto-shutoff valve.

Best,

Bob Jackson

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