Common Plumbing Problems Found During Home Inspections

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Plumbing problems are some of the top defects found in a home inspection. Water is essential to life and we use it for all sorts of activities in our daily lives. Which makes it imperative that your home inspector spends adequate time examining your home’s plumbing system.

Common plumbing issues found in home inspections are generally related to water leaks, sewer line clogs, water heater problems, and subpar plumbing work. The presence of one or more of these issues may require a full inspection from a licensed plumber.

Every day, we rely on plumbing to provide water to our home’s faucets, showers, toilets, water heaters, and even outside to our lawns and gardens. Some homes even use gas for their stoves, heating, and providing hot water all around the house. 

When these systems are working in harmony, it’s great, but when they aren’t, it can cause issues that have a knock-on effect right throughout the property. Some plumbing issues are glaringly obvious, such as a running toilet or dripping faucets, while others hide away behind walls or under the floor.

According to the EPA, “the average household’s leaks can account for nearly 10,000 gallons of water wasted every year and ten percent of homes have leaks that waste 90 gallons or more per day.” 

Fortunately, home inspectors are trained to spot both of these issues and will do their best to search for any evidence of plumbing deficiencies around the home.

Keep in mind that the inspector’s job is merely to observe and inspect potential problems around the home, which will then be reported in their home inspection report. All home inspectors must act per their state’s guideline, and the Standards of Practice set out by their respective associations such as ASHI or NACHI.

Home inspectors will provide a visual examination of the home’s plumbing system, including the operation of all plumbing fixtures. If the home inspector believes it to be necessary, they will recommend that you have the defect evaluated by a qualified plumber who will offer a more intensive investigation into the problem and give you repair recommendations. 

With that being said, let’s take a look at the most common plumbing issues that you will find during a home inspection.

1. Old & Defective Piping

old house plumbing

Let’s start the list with one of the most common issues that homeowners find with their plumbing, faulty or inadequate pipes. Almost every property will have pipes running right throughout the house, transporting gallons upon gallons of water each day. If one or more of these pipes has an issue, it can wreak havoc around the house in the form of leeks or contaminated water. 

Depending on the age of your house, you may have pipework that has now become inadequate since its installation. Some pipework materials are now considered to be illegal and even pose health risks. Let’s take a look at a few of the things that home inspectors will look out for.

Galvanized pipes

The galvanizing of pipes was a standard process that was used in homes that were built before 1960. In short, the galvanizing process is when you coat steel or iron with a protective layer of zinc to stop it from corroding. While this usually works for a while, galvanized pipes only have a life expectancy of about 20 to 70 years. 

Once the pipes have corroded, they are considered serious defects on a home inspection as they can become extremely prone to failure. In most cases, the galvanized pipework will have to be replaced entirely. To make matters worse, galvanized piping is linked to increased levels of lead in drinking water. 

In some cases, there is lead present in the zinc coating of the galvanized pipes, which eventually contaminates the water in the house. According to the Environmental Protection Agency, the presence of excess lead in the diet can lead to a variety of severe health conditions, ranging from cardiovascular disease to reproductive problems.

Galvanized piping tends to corrode from the inside out. The piping can look perfectly fine on the outside, but be corroded inside. As galvanized pipes corrode the diameter narrows which decreases water pressure and can cause the water to be brown due to rust in the water.

Polybutylene (PB) pipes

Polybutylene piping was used from 1978 to 1995 as it was often recommended to be the pipework of the future. Unfortunately, they failed to stand up to the test of time. Nowadays, polybutylene pipes are no longer accepted by the US building code, and they’ve stopped going through manufacturing.

If polybutylene (PB) piping is present on a home inspection, it will be raised and noted as a concern in the home inspector’s report. The main problem PB piping is that the material reacts to chlorine in the water system causing it to become brittle, crack, and eventually leak.

This material of polybutylene becomes fragile and brittle over time. After a few years of use, they will likely start to degrade from disinfectants and other regular household products running through the pipes. They are extremely susceptible to cracking, which will cause leaks throughout the home.

We still see polybutylene piping in houses today. Frequently, we find polybutylene piping leak-free at the time of the home inspection, but that doesn’t lessen the concerns about the piping because it could fail at any time, and it’s impossible to see the inner wall of the piping to get an accurate gauge of its true condition.

Polybutylene piping has been the source of class action lawsuits however information about these lawsuits have been removed from the internet.

“As of December 2016, all of the PB pipe class action, claims, litigation and settlement websites, links, and claims administrators listed below had been removed from internet access and the links return either a 404 not-found error message or they link to plumbing contractors who purchased the links to obtain business” according to

Rusted Cast Iron Pipes

Cast iron pipes are a relatively common occurrence, especially in older homes. Cast iron piping was the preferred piping method pre1970s. If your house has cast iron piping it may be perfectly fine. According to many plumbers, cast iron is the preferred piping method but just isn’t cost-effective in modern construction.

Cast iron waste piping is very quiet compared to other types of piping like ABS and PVC. The problem comes in when the piping rusts or begins to leak, repair can be quite expensive so most plumbers will look to replace the piping with PVC which is easier to handle and much less expensive.

ABS Waste Piping

Black ABS (Acrylonitrile Butadiene Styrene) drain piping was commonly used from the 1980s to the 1990s. This was first-generation piping used as an alternative to the growing expense of cast iron piping.

ABS piping can still be found in thousands of homes today and many people are not aware they have a problem. Investigations into ABS failures determined these problems arose from a failure to properly clean, prime, and glue the pipe joints during construction. Later ABS piping failures were determined to be attributed to the cracking of the piping itself.

ABS piping was also a part of a class-action lawsuit in and around 1985. Additional information on litigation and failures of ABS piping can be found at

A home inspector should note the presence of ABS piping and refer it for examination by a licensed plumber. Defects may exist that are not inside accessible areas that only specialized equipment or a licensed plumber can detect.

Uninsulated Plumbing Pipes

Water supply pipes that are not properly insulated can freeze and burst in the winter during times of freezing temperatures. As water freezes it expands causing the pipes to crack. Once the frozen line thaws, a leak will develop.

Water pipes that are particularly vulnerable are those inside unfinished areas like basements and crawl spaces as well as exterior piping for hose bibs, outdoor sinks, and outdoor showers.

2. Clogged Sewer Lines

A sewer line clog is something that you really don’t want to have to deal with. If left unrepaired it could eventually lead to raw sewage backing up out of the drains, which can cause considerable damage to the property. The problem with this is that it is particularly hard to diagnose, and the pipework is located underground. 

Fortunately, the sewer line should start giving you warning signals before it’s too late, such as gurgling sounds and slow draining issues, commonly accompanied by a foul smell. Eventually, the wastewater will back up into your home as it has nowhere else to go, and you will start to get very unpleasant spillages around the property. 

A clogged sewer line can be caused by many things, mainly broken sewer lines that fill with dirt and tree roots growing into the sewer line.

According to Mr. Rooter Plumbing, “don’t try to use drain cleaner to unclog the sewer line. It won’t work and could make the problem much worse. The chemicals in drain cleaner are very caustic and have eaten through older pipes before, causing even more damage.”

3. Water Heater Problems

According to the NACHI, the home inspector will inspect “the water heating equipment, including the energy source, venting connections, temperature/pressure-relief (TPR) valves, Watts 210 valves, and seismic bracing.”

A home inspector will check for any signs of defects that prevent the water heater from working as it should. As this is a vital part of the home, especially during the wintertime, it makes for an important aspect of the entire plumbing check. 

Some common issues to look out for include:

4. Cross Connection Issues

Cross connection issues occur when the plumbing fixtures allow contaminated water to enter back into potable water. If the usual pressure of the water system is disrupted, and the water level is above the faucet with no air gap or backflow preventer, backflow can occur and the home’s water supply becomes contaminated.

If the filtered drinking water becomes contaminated by your laundry or bathwater, the chemicals will make it unsafe to consume. This condition is common in older homes and DIY installations.

Many appliances come with backflow preventers already incorporated, but some will need to have backflow preventers installed. In fixtures that pose a more hazardous risk of contamination, the preventers should be tested annually to ensure they are working efficiently. 

The home inspector will keep a lookout for any obvious cross-connection issues throughout the house during the inspection of appliances such as dishwashers, washing machines, bathroom fixtures, and sump pumps. 

5. Slow Draining Sinks

Slow draining sinks are a relatively frequent occurrence in homes. It is one of the most common problems with your plumbing system, and most of the time, there is no need for immediate concern. Usually, slow draining skinks occur due to blockages, such as hair, toothpaste, and soap accumulation.

Most of the time, this can be cleaned up pretty quickly with some drain cleaner. However, it is worth noting that sometimes these chemicals can do more harm than good. 

If the slow drain is isolated to one fixture, it’s likely a small clog isolated to that fixture. Multiple fixtures are backing up point to a more serious problem.

That being said, slow draining sinks can point towards bigger issues such as tree roots blocking the main lines. The home inspector will note this down as a minor defect, and it will usually require a video inspection from a professional plumber to diagnose the exact issue.

Unclogging a sink may require a plumber snaking the line to force obstructions free. Stubborn clogs could require the plumbing to be dismantled to check and remove obstructions from the piping.

6. Dripping Faucets

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During the assessment, the home inspector will inspect the interior water supply, including all fixtures and faucets, by running the water. The home inspector will report any active faucet leaks that they observed and any deficiencies of the water faucets around the home. According to the EPA, a faucet dripping one drip per second can account for a loss of over 3000 gallons of water per year.

Faucet leaks are relatively easy to repair. Most leaks are caused by worn O rings in the faucet itself. However, it some instances the faucet may require replacement.

It’s worth noting that a faucet can leak from places other than the spout itself, such as the base of the faucet and under the sink. If these leaks go unnoticed, they can cause substantial damage to the cabinetry under the sink.

7. Low Water Pressure

Low water pressure can be one of the most frustrating problems to have with your home. Imagine you’re trying to take a shower and the water is barely dribbling out of the showerhead, it becomes more of a nuisance than an enjoyable shower experience. 

Low water pressure can be isolated to a single fixture or affect multiple fixtures. A faucet aerator can be the source of the low water pressure if it only occurs at one fixture.

However, if you experience low water pressure at multiple fixtures can hint to a more serious issue. Let’s look at some of the causes of low water pressure at multiple fixtures.

  • Main Water Source Issues – If you are experiencing low water pressure in your home, you could have an issue at your main water source. If you have a public water source, there may be a leak before the water meter. If you have a private well, you may have a faulty pressure switch or have the pressure switch dialed down to low.
  • Water Heater Issues – You may have a leak at your water heater, causing you to lose water pressure. Check the water inlets and outlets connections, a faulty temperature and pressure relief valve, or worse, a leak at the bottom of the water heater.
  • Water Supply Pipe Leaking – You may have a supply pipe leak somewhere in the water supply piping. This may involve having to have a thorough examination of the system by a licensed plumber to find the leak. Look for areas behind tubs and showers, wet areas of floors or drywall, at supply pipe shut off valves located under sinks and toilets, inside crawl spaces, and inside basements to try and find the leak.
  • Water Supply Piping – Galvanized piping can narrow the interior diameter of the piping over time, which reduces water pressure. Older supply piping was also commonly 1/2″ in diameter rather than the current standard of 3/4″ diameter. Smaller piping can reduce water pressure, and the only remedy would be to replace the piping.

8. Toilet Problems

Toilets fail for numerous reasons. A toilet that doesn’t flush likely indicates an obstruction inside the main sewer pipe. If the clog is bad enough, the toilet could back up and overflow.

Clogged Toilet

A clogged toilet happens for many reasons and is much more frequent in homes with older plumbing systems. The best way to deal with this is by using a plunger and some drain unblocker. However, this all depends on what is causing the issue in the first place.

For severe blockage, the toilet may need to be taken up to allow for a sewer scope of the piping to look for blockages. More modern homes, have plumbing clean outs to allow for investigation without removal of the toilet.

However, if the clog is inside the toilet itself, a plumbing snake can usually free the clog.

If a home inspector spots that a toilet is clogged, this will be noted as a defect, and they will likely ask for you to see an opinion of a professional plumber. 

Toilet Continuously Running

Similarly, if the toilet is continuously running and is wasting water in the house, this will also be noted as a defect that needs attending to. The excess running of water makes your home susceptible to leaks and places your plumbing system under excess stress, not to mention the negative effect it has on the environment and your water bill. 

Often a continuously running toilet is due to a flapper that is not sealing properly inside the tank. This is a relatively easy repair for most homeowners.

Toilet Tank Leaking

Toilets have two main parts; the base and the tank. The tank is bolted to the base and have seals to prevent it from leaking. If you notice water coming from the bottom of the tank and the bolts are rusted, it’s time to change the hardware and seals.

Loose Toilet

Whether caused by age or use, toilets will eventually become loose at the base and leak. Toilets have a wax seal that sits between the flange and the base of the toilet. If your toilet is loose at the base, it’s time to replace the seal and reset the toilet. Left unrepaired, a leaky toilet seal can rot out the subfloor under the toilet.

Repairing a loose toilet is a relatively easy job provided the floor is solid, however if you’re uncomfortable doing it you should call a plumber. It’s important to replace the bolts when you reset the toilet to ensure a secure fit.

9. Undetected Leaks in Walls

Hidden leaks in the wall or under the floorboards are among the biggest causes of water wastage in the USA. In fact, the average household leak in the USA accounts for nearly 10,000 gallons of wastewater each year.

These hidden leaks can go on for months or even years before they are found. Most of the time, they are completely silent, which makes them so notoriously hard to detect. 

If leaks are left untreated for a considerable amount of time they can cause some very serious issues throughout the house, such as:

  • Foundation shifting – water is the one number source of foundation movement. Leaks that go on for a considerable amount of time can erode the soil causing foundations to shift and move.
  • Cracking – water leaks inside walls or in basements and crawl spaces can allow spot settlement which can cause cracks to form in exterior or interior walls.
  • Mold & mildew – one of the most common issues concerning water leaks is mold and mildew. Mold and mildew form when mold spores present in the air begin to form growth on wet surfaces. Mold and mildew can grow on surfaces where moisture exceeds 20%. Active mold growth in a house can lead to respiratory illnesses, allergic reactions, and asthma.
  • Uneven floors – water leaks in basements and particularly in crawl spaces that are not repaired can cause settlement which can cause uneven floors due to settlement or wood rot.

Fortunately, most of these leaks can be fixed with a spot of DIY or a quick call out for a licensed plumber. Most leaks are pretty easy to repair and may be as simple as fixing a leaky faucet or one loose pipe. However, left unrepaired can create a wave of problems that can cost thousands of dollars to repair. 

The difficult part usually lies in noticing the problem, not in the repair. That said, let’s take a look at some of the most common symptoms of a hidden leak and what home inspectors will look out for during their assessment:

  • Peeling or bubbling paint on your walls – look for signs of peeling or bubbling paint on wall surfaces.
  • Dark stains on the wall or ceiling – these stains can indicate that a leak is present in a hidden area that has appeared for no apparent reason. Don’t ignore it. Examine the staining or call in a licensed contractor to do so for you.
  • Musty smells in the home – A persistent musty smell that is lingering around the house could indicate a leak is present in your home. This often comes from damp crawl spaces or basements.
  • Buckling walls and flooring – Are your floors cupping or curling at the joints? This can occur in most types of floor coverings, but particularly in wood, laminate, and vinyl surfaces.
  • An abnormally high water bill – If you see a sudden spike in your water utility bill and have had no major changes in your household, you likely have a plumbing leak and should call a plumber immediately to investigate.

10. Jammed Waste Disposal

A jammed waste disposal is simply clogged because too much was stuffed down the disposal causing the blades to stop spinning. Freeing a jammed disposal is fairly easy to do.

If the disposal will not turn on, chances are the reset button has tripped because the under is jammed. The reset button is a red button located on the bottom of the disposal. Check the button to see if it has tripped and reset it if needed.

Plumbing Issues & Their Estimated Repair Cost

If you conducted a home inspection and you’re thinking about buying a property that’s pulled up some plumbing issues on the report, you may want to know how much it’s going to cost before you sign on the dotted line.

It’s a good idea to renegotiate the existing deal with the seller to account for the repair costs that you will incur.

According to, the cost of a plumber ranges from $175 to $450 for a typical job with the average cost per hour ranging from $45 to $200.

Here are the average costs for common plumbing issues:

Plumbing IssueRepair Cost
Burst pipe$150 – $350
Full plumbing system replacement$10,000 – $15,000
Sewer line unclogging$200 – $500
Water heater fix$550 – $1,500
Leak damage correction$1,140 – $4,730
Low water pressure$250 – $350
These numbers are estimates. Total repairs will vary based o the severity of the condition.

Final word

Plumbing issues are one of the most commonly reported defects in a home inspector’s final report. These issues are often hard to spot with an untrained eye and can rack up thousands in repair bills if left untreated.

Most of the time, these issues are pretty easy to fix as long as you catch them early enough, and the damage isn’t already done. If you are a homeowner, make sure you check for any signs of hidden leaks behind the walls or underneath the floorboards.

If these are left for too long, they can waste thousands of gallons of water each year and seriously affect your house’s structural integrity. It is better to keep on top of the problems while you occupy the house to avoid the big bills that occur when the problems go unchecked.


Hubert Miles | Licensed Home Inspector, CMI, CPI

Hubert Miles is a licensed home inspector (RBI# 2556) with more than two decades of experience in inspection and construction. Since 2008, he has been serving South Carolina through his company, Patriot Home Inspections LLC. As a Certified Master Inspector, Hubert is dedicated to providing his expertise in home inspections, repairs, maintenance, and DIY projects.