Plumbing Red Flags to Watch for During a Home Inspection
- Local R&P
- Aug 8
- 5 min read
When you're buying a home in San Jose—or anywhere in the Bay Area—a professional home inspection is a must. While structural issues and roof conditions are usually top of mind, plumbing problems can be some of the most expensive (and stressful) surprises for new homeowners. That's why it's important to recognize plumbing red flags early during the home inspection process.
In this article, we’ll break down the most common plumbing issues inspectors look for, signs that a system may be hiding bigger problems, and what to do if you spot a red flag. If you're in the San Jose area, this guide can help you decide when it’s time to bring in a trusted local plumber for a second opinion.
1. Low Water Pressure
Low water pressure may seem like a minor inconvenience, but it can be a sign of serious underlying issues, such as:
Corroded or clogged pipes
Leaks in the plumbing system
Faulty pressure regulators
A failing water heater
During a home inspection, faucets and showers are typically tested. If water pressure is noticeably low, especially in multiple locations, the issue may be systemic. In older San Jose homes, galvanized steel pipes are a common culprit—they corrode from the inside and slowly restrict water flow.
👉 Pro Tip: If you notice low pressure, request that a licensed plumber performs a pressure test and checks for pipe corrosion before closing the deal.
2. Visible Pipe Corrosion or Leaks
A visual inspection of accessible plumbing—such as in basements, crawl spaces, or under sinks—can reveal:
Rusted pipes
Water stains
Dripping joints
Mold or mildew buildup
San Jose homes built before the 1970s may still have outdated piping, which is more prone to corrosion and leaks. If the home inspector spots any of these signs, they may recommend further evaluation from a licensed plumber.
🛑 Red Flag Alert: Discoloration or flaking on copper or galvanized pipes often indicates corrosion and may mean the plumbing is nearing the end of its lifespan.
3. Water Heater Issues
The water heater is one of the most expensive plumbing components in a home. Common inspection red flags include:
Water pooling around the base of the heater
Rust on the tank or in the hot water
Old age (over 10–12 years)
Strange noises or smells
In San Jose, where utility costs are already high, an inefficient or failing water heater can lead to skyrocketing energy bills. If the inspector notes any of these signs, consider requesting a replacement or repair as part of your purchase negotiation.
🔥 Quick Tip: Ask the seller for maintenance records and check the water heater’s manufacture date. If it’s close to the end of its service life, plan to budget for a new unit.
4. Sewer Line Problems
Sewer lines are usually underground and not part of a standard home inspection. However, any signs of a potential sewer issue are a serious concern:
Frequent drain backups
Strong odors in the yard or basement
Slow drains in multiple fixtures
Lush patches of grass (indicating leaks)
In San Jose, older homes often have clay or cast iron sewer lines, which can crack or collapse over time. Tree roots are also a major issue in neighborhoods with mature landscaping.
💧 What to Do: If the inspector suspects a sewer problem, hire a plumber to perform a sewer camera inspection. This service can save you tens of thousands in future repair costs.
5. Poorly Done DIY Repairs
It’s not uncommon for homeowners to attempt plumbing repairs on their own. Unfortunately, DIY fixes often lead to more problems than they solve.
Watch out for:
Mismatched pipe types (e.g., PVC connected to copper without proper fittings)
Overuse of plumber’s tape or caulk
Unpermitted water heater installations
Missing or incorrect drain traps
In California, code compliance is especially important when it comes to resale value and insurance claims. If the inspector flags shoddy plumbing work, call in a licensed plumber to evaluate the repairs and estimate the cost to bring everything up to code.
6. Leaky Toilets or Loose Fixtures
Toilets that rock, leak at the base, or constantly run may seem like small issues, but they can waste water and cause subfloor damage. Look for:
Water stains around the toilet base
Loose handles or seats
Dampness or musty smells around the bathroom
In multi-bathroom homes, check each toilet and faucet. Leaks in one area often suggest neglected maintenance throughout the house.
🚽 Expert Note: A new wax ring or toilet flange is a small repair, but if the subfloor is damaged, the costs rise quickly. Get an expert plumber's opinion to avoid surprises after move-in.
7. Inadequate Water Drainage
Improper drainage is a silent issue that many buyers overlook—until heavy rain hits.
Common signs of poor drainage include:
Water pooling near foundation or crawl space
Soggy yard areas
Clogged or missing yard drains
Water stains in the basement or garage
In San Jose’s hillside and older residential areas, homes may have outdated drainage systems or no French drains at all. These problems can lead to foundation damage, mold, and erosion.
🌧️ Next Step: Have a plumber check that downspouts, sump pumps, and exterior drainage are functioning and up to code.
8. Noisy Pipes or Water Hammer
Banging, rattling, or vibrating pipes—known as “water hammer”—are often due to:
Poorly secured pipes
Air chambers that have lost pressure
Sudden valve closures
While this issue isn’t always serious, it can damage pipe joints over time and create leaks. If the inspector hears any plumbing noises, don’t ignore them.
🔧 Fix It Tip: A licensed plumber can install hammer arrestors or secure loose piping to prevent long-term damage.
9. Outdated or Non-Code Plumbing Systems
In California, plumbing codes are updated regularly for health and safety reasons. Many homes—especially those over 40 years old—may have:
Polybutylene pipes (known to fail)
Lead supply lines (health hazard)
Improper venting
Unpermitted plumbing work
If your inspector suspects the plumbing doesn’t meet current California code, it’s essential to get a full plumbing evaluation. In San Jose, the cost to replace outdated plumbing can range from $5,000 to $20,000+, depending on the home size and complexity.
✅ Bonus: Upgrading outdated systems not only ensures safety but also adds resale value and qualifies for rebate programs in some cases.
10. Mold or Mildew Near Plumbing Fixtures
Even if you don’t see active leaks, mold and mildew can signal hidden moisture problems. Common areas include:
Under bathroom and kitchen sinks
Behind toilets or tubs
Inside cabinets
Around baseboards
Not only is mold a plumbing red flag, but it’s also a potential health hazard. In San Jose’s humid microclimates, it can spread fast if not addressed.
Final Thoughts: Don’t Let Plumbing Surprises Drain Your Wallet
Plumbing problems may be hidden behind walls or underground, but a thorough home inspection combined with the eye of a licensed plumber can help protect your investment. If you’re buying a home in San Jose or the surrounding areas, don’t overlook these plumbing red flags.
At Local Rooter Corp., we’ve helped hundreds of homeowners and real estate professionals with pre-purchase plumbing inspections, sewer line camera inspections, water heater evaluations, and full system replacements.
If you want peace of mind before moving forward on a home purchase, give us a call at (408) 868-8759 or schedule an inspection online. Our team is local, licensed, and ready to help you make a confident decision.
Call to Action
📞 Call Local Rooter Corp. today at (408) 868-8759
📍 Serving San Jose, Santa Clara, Milpitas, and the Bay Area💧 Trusted. Licensed. Affordable.
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