Water is a first rate destroyer of homes. Only a fire will damage or destroy a home faster, and proper supply and removal of water is vital to maintaining the integrity of the structure. While barriers like roofing and siding keep external water and moisture away from your home, it’s the plumbing system that keeps internal water from damaging its surroundings.

In a standard home inspection, much of the plumbing system will be hidden behind the walls, buried in the yard, or otherwise not available to be inspected. You’ll need to check the obvious parts of exposed plumbing, but also look for signs of water stains on walls or ceilings that indicate a larger, hidden issue.

A home’s plumbing involves everything that brings water into the home, delivers it for use at a fixture, removes the waste water from the home, and the vent system that allows the traps to remain effective.


Fixtures are the easiest part of the plumbing system to inspect. Most people have a pretty good idea of how a sink or toilet is supposed to work, and can test one simply by using it.

Run water through sinks, tubs, and showers, as well as any appliances that use water, such as washing machines and dishwashers. On faucets, make sure both the hot and cold water is functioning. Fill up sink basins and let them sit for a few moments to make sure they hold water. Once satisfied, let them drain, checking for any leaks in the drain as all the water exits at once.

Look for any leaks at the spouts or base of faucets, and check for any signs of old leaks under vanities and on the floor around fixtures. It’s not unusual to see signs of water damage around a tub or shower caused by inadequate caulking or other failed water diversion. This water damage may not be caused by faulty plumbing, but the plumbing inspection is an excellent time to look for it. Lastly, give the fixture a shake—not too vigorous, just enough to be sure that the fixture is properly secured.

Supply and Drain Pipes

Supply pipes are relatively easy to inspect. Because they’re pressurized, any poor connection or leak will normally spray out, and very quickly create a big enough wet area that you won’t miss it.

Poorly sealed drain lines only leak when water moves through them, so a leak might go much longer without being detected. Without doing a pressure test, there’s no way to know for sure that there’s not a leak, so it’s important to look for secondary signs, such as water stains or symptoms of dry rot.

One of the few places to get an unimpeded look at drain lines is an unfinished basement. Look over the lines for signs of deterioration, especially on metal pipes. While you’re at it, give any visible horizontal runs a once-over to make sure that it’s sloping down over the course of its run to the stack. (The “stack” is the large vertical drop where multiple drain lines converge before heading out to the sewer or septic system. It is usually easily identifiable because of its larger diameter.)

Every plumbing fixture should have a trap. In addition to being a great safety net in case of a valuable dropping down the drain, they provide a water plug, keeping sewer gases from entering the home. While some traps aren’t visible (washing machine drains, for example, are often hidden in a wall) check beneath any that you can see to make sure no water is seeping out.


Just as every drain needs a trap, every trap needs a vent. The venting system of the home allows gases to escape and keeps the drain system working properly. Each drain must have either a connection to a vent line or an air admittance valve (AAV)–a small device that allows air to enter the vent system, but prevents it from seeping out into the home.

The main indicator of a problem with the vent line is an unpleasant odor or “sewer smell.” Check that the vent line leads out to the roof and that the vent pipe on the roof is unobstructed from debris or animal nests.

Water Heaters

A traditional water heater heats and stores water in reservoir tanks, using either gas-fueled flame or an electrical heating element. If you see water on the floor, locate its source. If it’s leaking from the pressure release valve (a valve located at around chest-height with a pipe allowing overflow to exit near the floor) then it’s possible that only that PRV needs to be swapped out. If the water is coming out of the bottom of the tank, chances are that the whole water heater will need to be replaced.

Tankless water heaters are a more straightforward inspection. Without the issue of hot water storage, simply run the hot water at a nearby faucet and make sure that the water comes out at the correct temperature. Once you know how the water heater functions, make sure that it vents properly, if it’s a gas unit. Different manufacturers have different specs on whether they require stainless steel or PVC vent lines, and on whether or not they require horizontal or vertical vent lines. You’ll need to check the specs for a specific model number to verify proper installation.  All vents, however, should exit the home away from any soffit vents or other places that might allow for carbon monoxide re-entry to the home.

Note that gas heaters will likely have condensate lines or trays. Condensate is a natural byproduct of combustion; the condensate collection device should be corrosion resistant, and if it’s a condensate line rather than a tray, it should feed into an appropriate drain.

Septic Systems and Wells

Not all homes have these features, but those that do should have them inspected. Like the drain and supply lines inside a house, septic systems and wells are largely hidden from casual view. In fact, some homeowners who’ve been lucky enough to not have much issue with them may be unsure about where they are located on the property.

Both septic systems and wells require specialized skills to deal with, and if you’re unfamiliar with them, it’s a good idea to call in a qualified technician. However, there are a few general things that can be checked on your own.

Septic systems should be properly sized for the home; a 1,000 gallon tank should handle homes with up to three bedrooms. (However, some municipal codes have different requirements, so the tank size requirements for your home may be different.) A properly sized tank should have to be pumped no more than once every few years. Check the tank to see when it was last pumped. And of course, there should be no liquids rising to ground level around the tank or in the leach fields.

When inspecting wells, the main concerns are location and water quality. For example, if a property has both wells and a septic system, the well should be at least 50 feet from any septic tank or leach fields. Other materials that have restrictions on well proximity include livestock yards, underground gas tanks, and pesticide or fertilizer storage. If you see anything on the property that jumps out at you as something you wouldn’t want in your drinking water, it’s worth checking with the National Ground Water Association to see if it’s sufficient distance from the well.

To check water condition, you can use a store-bought testing kit or contact local health departments to find out what options are available in your area.


Lastly, don’t be afraid to question anything that looks off to you during a plumbing inspection. While the specifics of plumbing can sometimes be confusing, the basics rules are accessible to most people: water and waste should stay inside the pipes, and water flows downhill. Keep these principles in mind, and if you see anything that seems troubling, go ahead and take a closer look—you’re far better off taking a little more time during an inspection than discovering that you missed something later on.


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