The Most Common Plumbing Issues Found During Home Inspections

A home can look perfectly fine until the inspection report says otherwise.

During a walkthrough, everything may seem to be working as expected. Then the inspection identifies a plumbing issue that was never obvious during everyday use. It might be a slow leak, a drainage problem, signs of an aging sewer line, or another issue that deserves a closer look.

That is where many buyers and sellers are left with questions. Which findings are minor? Which ones should be addressed before moving forward? And which ones need a plumber to take a closer look?

In this blog, you’ll learn about the plumbing issues most commonly found during home inspections, why they matter, and what those findings could mean before you buy, sell, or negotiate on a home.

Leaking or Dripping Fixtures

This is the most frequently flagged plumbing item on home inspection reports. Faucets that drip, toilets that run, and supply connections that seep may seem minor, but inspectors document them because they signal wear.

A dripping faucet often means a worn cartridge or valve seat inside the fixture. A toilet that runs continuously usually points to a failing flapper or fill valve. Supply connections under sinks that show moisture or mineral staining at the fittings indicate a slow leak that has been present for some time.

These findings rarely kill a deal, but they give buyers leverage to request repairs or negotiate the price. For sellers, addressing them before the inspection removes low-cost items that can stack up and create a negative impression in the report.

Slow or Clogged Drains

Inspectors test every drain in the home by running water and timing how quickly it clears. A slow drain gets documented, and a drain that does not clear at all gets flagged as a deficiency.

In older homes, slow drains are often caused by decades of buildup inside the pipe. Grease, mineral scale, and corrosion narrow the interior diameter and restrict flow. In homes with mature trees, root intrusion through cracked sewer lines is a common contributor.

A single slow drain may only need a professional drain cleaning to resolve. Multiple slow drains or a backup during the inspection suggests a main line issue that goes deeper than any one fixture. In that case, the inspector may recommend a camera inspection of the sewer line to determine the scope.

Water Heater Age and Condition

Home inspectors check the water heater’s age, condition, and safety compliance. A unit that is past its expected lifespan, showing signs of corrosion, or missing required safety features will be documented in the report.

The most common findings include:

• A water heater older than 10 to 12 years with visible rust at the base
• A missing or improperly installed temperature and pressure relief valve
• No discharge pipe on the T&P valve, or one that terminates too high above the floor
• Sediment noise during operation
• Signs of previous leaking around the base

A water heater flagged on an inspection report often becomes a negotiation point. Buyers may request a replacement before closing, a credit toward the cost, or a price reduction. Sellers who replace an aging unit before listing avoid that negotiation entirely and present a cleaner report.

Outdated or Non-Compliant Pipe Materials

Inspectors identify the visible pipe materials in the home and note any that are outdated or no longer meet current building codes.

The materials that consistently get flagged include:

• Galvanized steel supply lines that are corroding and restricting flow
• Lead pipes or lead-soldered joints in homes built before 1986
• Polybutylene supply lines that are prone to sudden failure
• Cast iron drain lines showing advanced corrosion

Each of these findings carries a different level of urgency. Lead pipes are a health concern that may need to be addressed before occupancy. Galvanized and polybutylene lines are failure risks that a plumber should evaluate for remaining useful life. Cast iron drains may still function, but are likely approaching the point where sewer line repair or replacement becomes necessary.

Improper or Missing Shut-Off Valves

Every fixture in the home should have an accessible shut-off valve that allows the water supply to be isolated without turning off the main. Inspectors check for the presence and functionality of these valves.

Common findings include:

• Missing shut-off valves under sinks or behind toilets
• Valves that are corroded or seized and cannot be turned
• Gate valves that no longer close fully due to internal wear

Missing or non-functional shut-offs are a problem because they eliminate your ability to isolate a leak quickly. If a supply line bursts under a sink with no working shutoff, the only option is to run to the main valve and shut off water to the entire house. Functional shut-off valves at every fixture are a basic safety feature that inspectors take seriously.

Signs of Water Damage from Plumbing Leaks

Inspectors look for evidence that a plumbing leak has caused or is currently causing water damage. These findings are among the most serious in any inspection report because they indicate both a plumbing failure and structural consequences.

Signs include:

• Staining or discoloration on ceilings below bathrooms or kitchens
• Soft or warped flooring near fixtures or under sinks
• Mold or mildew in areas that should be dry
• Peeling paint or bubbling drywall near plumbing runs
• Musty odors in enclosed spaces like cabinets and crawl spaces

When an inspector documents water damage, the next step is usually a plumber evaluating the source and a contractor assessing the scope of the structural damage. A water damage finding on an inspection report can delay or derail a closing if the cause and extent are not determined quickly.

Sewer Line Concerns

Some inspections include a sewer camera evaluation, and many buyers request one separately for homes with older plumbing.

The camera reveals conditions that no surface inspection can catch: root intrusion, pipe deterioration, joint separation, bellies that trap waste, and partial or full collapse. These findings are significant because sewer line repair or replacement is one of the most expensive plumbing projects a homeowner can face.

Even without a camera, inspectors note surface-level signs of sewer problems:

• Unusually green patches of grass over the sewer line path
• Standing water or soggy ground in the yard
• Sewage odors near floor drains or outside
• Evidence of previous sewer work that may not have been permitted

If you are buying a home built before the 1980s, a sewer camera inspection is one of the most valuable add-ons you can request. The cost is minimal compared to the cost of discovering a failed sewer line after closing.

Prepare for What the Inspector Will Find

Plumbing issues on a home inspection report are not deal-breakers by default. Most of them are repairable, and many are negotiable. What turns a finding into a problem is when neither the buyer nor the seller understands the scope, the cost, or the urgency of the repair.

If you are buying and the inspection flags plumbing concerns, or selling and want to address issues before they show up on the report, a local plumber can help. They can evaluate the findings and give you a clear picture of what needs attention now and what can wait. 

LaCassa Plumbing has been helping homeowners in Naperville and the surrounding suburbs navigate exactly this situation since 2018. Give us a call and let us help you understand what the inspection is telling you.