That pipe coming out of lower part of the wall of your home, or coming up from the ground near the wall, could be any one of these three things:

1) Temperature and Pressure Relief (TPR) discharge pipe for water heater - The TPR valve at the side of the water heater is required to extend to an exterior location and terminate pointing downward. The water is water is dripping because the valve has opened, either because the water heater is overheating or the valve is malfunctioning. Find the TPR valve at your water heater and feel the discharge pipe directly below the valve. If it is warm, this is the source.
    If the water is coming out at just a slow drip, it is because the valve is leaking and should be replaced. If it is flowing steadily, then it is likely the valve has opened because the thermostat at the water heater has failed and the unit is overheating. Either way, repair is necessary.

2) Drain pipe for catch pan under water heater - The drain pan under the water heater is required to have a drain pipe to the exterior, to avoid flooding the home if the water heater starts leaking. Also, in some homes, the TPR valve terminates into the catch pan. Check the catch pan under the water heater for standing water. Again, repair is necessary.

3) Condensate drain line for indoor unit (air handler) of air conditioner - As part of the cooling your home, the air conditioner is also dehumidifying the air. The indoor air handler collects the water and drains it to the ground, usually near an exterior wall. This is normal, but will only occur when the system is operating and for a few minutes afterward.

4) Condensate drain line from high-efficiency gas furnace - If your furnace is the high-efficiency type that has PVC pipe flues, then it may be a drain pipe for the condensate that the furnace creates as part of squeezing every last BTU it can out the gas combustionl. There may also be a small collector cup and drain visible at the side of the furnace.

    If the leaking pipe is sticking down from the soffit of the house, see our blog post What is the small pipe sticking out of the eaves/soffit under the roof overhang?

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Here’s links to a collection of our other blog posts about PLUMBING PIPES:

• How can I protect my pipes to keep them from bursting during a hard winter freeze in North Florida?

• Can galvanized steel pipe still be used for new water lines in a house? 

• How can I tell if I have cast iron pipes in my house? 

• Why can't a sanitary tee be used for a horizontal-to-horizontal drain pipe connection? 

• What is the difference between green and white sewer drain pipes?

• Is a washing machine drain hose required to be secured at the standpipe?

• What are the abandoned pipes sticking out of the wall in my house?  

• What are the code requirements for plumbing vent terminations?

• What are the code requirements for layout of drain piping under sinks?

• What causes a gurgling sound when a bathtub or sink drains? 

• What is a "combination waste and vent" in a plumbing system? 

• What is a building trap?  

• What is a galvanized nipple?

• What are the pipes sticking out near my water valves?

• How do you accurately find a broken water pipe leak under the floor slab?

• What is the difference between water pipe and sewage (waste) pipe? 

• Are plastic pipes (PVC, CPVC, and PEX) safe for drinking water? 

• Is a hot water faucet handle required to be on the left? 

• What is a dielectric union? 

• What's that powdery crust on the pipe connections at the water heater? 

• If all the plumbing drains have water in them and you can still smell sewer gas, what's causing the problem?  

• How can I tell what type of plumbing pipe I have?

• Why is there a flexible accordion pipe under the sink? 

• What is the difference between PVC and ABS plumbing pipe?

• What is the difference between water service pipe and water supply pipe? 

• What are the pipes on my roof? 

• How can I find out what type of water pipe runs underground from the water meter to the house (service pipe)?

• What is a P-trap?

• Why is old galvanized steel water pipe a problem for homebuyers?

• What does polybutylene pipe look like? Why is it a problem? 

• Which water pipes are an insurance problem and possibly uninsurable?

• Can you connect CPVC pipe directly to a gas water heater?  

     Visit our PLUMBING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.