A Plumber Created Guide to Evaluating a Home's Plumbing Before You Buy

You can check yourself:

• Water pressure and flow at multiple fixtures
• Visible pipe materials in accessible areas
• Water heater age and basic installation
• Fixture condition and operation
• Signs of leaks, stains, or water damage
• Drain speed and sounds

You’ll need a professional for:

• Sewer line camera inspection
• Hidden leak detection
• Gas line safety evaluation
• Code compliance assessment
• Water quality testing
• System sizing evaluation

What Adds Value

• Copper or PEX supply lines — Copper has a long lifespan and is durable. PEX is flexible, resistant to freezing, quieter, and easier to repair.
• Clean, organized routing — Straight runs with proper supports indicate professional installation.
• No excessive joints or patchwork repairs — Fewer connections mean fewer potential leak points.

Red Flags

• Galvanized steel pipes — Common in older homes. They corrode internally, restrict water flow, and are often near end-of-life.
• Mixed pipe materials — Indicates piecemeal repairs and can create galvanic corrosion.
• Low or inconsistent pressure — May point to internal corrosion or undersized piping.
• Poor workmanship signs — Solder joints with hanging drips, greenish corrosion, crooked pipe runs.

How to Inspect It Yourself

1. Check visible pipes — Look under sinks, in the basement, garage, or utility areas. Copper is reddish-brown. PEX is flexible plastic (red for hot, blue for cold). Galvanized steel is gray and often has threaded fittings.
2. Test water pressure — Turn on the kitchen faucet full blast. Then flush a toilet. If the faucet pressure drops significantly, the system may be undersized or corroded.
3. Run multiple fixtures — Turn on two or three faucets simultaneously. Significant pressure drop tells you the supply lines may be restricted.
4. Time the hot water — Note how long it takes for hot water to reach each bathroom. Long waits mean wasted water and higher bills.
5. Look at pipe joints — Clean, even solder joints indicate professional work. Drips, discoloration, or green corrosion suggest problems.

What Adds Value

• PVC or ABS drain lines — Modern, reliable, easy to service, not susceptible to corrosion.
• Proper venting — Fixtures drain quietly with no gurgling sounds or sewer odors.
• Cleanouts in accessible locations — Indicates forethought and allows for easier maintenance.

Red Flags

• Cast iron drains — Can last decades, but interior corrosion is common. Look for rust, flaking, or staining.
• Sewer odors — May indicate venting issues or failing traps.
• Slow drains across the house — Could signal main line problems.
• Large trees near the sewer line path — Roots seek out pipe joints and can cause expensive damage.

How to Inspect It Yourself

1. Run every drain — Fill each sink, then release. Watch how quickly it drains. Slow drains in multiple locations suggest a main line issue.
2. Listen for gurgling — While one fixture drains, listen at others. Gurgling indicates venting problems.
3. Smell for sewer gas — Check bathrooms, especially ones that may not be used often. Sewer odors mean something’s wrong.
4. Flush toilets and watch — The flush should be strong and complete. Weak or slow flushes can indicate drain line issues.
5. Look at the yard — Note where large trees are located relative to where the sewer line likely runs (usually a straight path from the house to the street).
6. Find the cleanouts — Look for capped pipes (usually 3-4” diameter) near the foundation or in the yard. Accessible cleanouts make future maintenance much easier.

What Adds Value

• Newer unit (within 8–12 years) — Tank heaters have a finite lifespan.
• Proper installation — Seismic strapping, drain pan with discharge line, T&P valve properly piped to the exterior or drain.
• Tankless systems — Endless hot water, higher efficiency, 20+ year lifespan.

Red Flags

• Old unit near end-of-life — Check the manufacture date.
• No drain pan — Especially concerning in finished areas where a leak causes damage.
• Improper venting — Gas water heaters need proper exhaust. Backdrafting puts carbon monoxide in the home.
• Evidence of past leaks — Rust, water stains, or corrosion around the base.
• Missing safety components — No seismic straps, plugged T&P valve, no expansion tank on closed systems.

How to Inspect It Yourself

1. Find the age — Look at the data plate on the water heater. The serial number usually encodes the manufacture date. Search “[manufacturer name] serial number decoder” to translate it.
2. Check for rust and corrosion — Look at the top, bottom, and connections. Rust at the base often indicates internal tank failure is coming.
3. Look for a drain pan — There should be a pan underneath with a discharge line, especially if the unit is in a finished space or upper floor.
4. Verify seismic strapping — California requires earthquake straps. Two straps—one in the upper third, one in the lower third—should secure the tank to the wall.
5. Check the T&P valve — It should have a discharge pipe running down and terminating near the floor or to the exterior. If it’s capped or plugged, that’s a serious safety hazard.
6. Test hot water delivery — Run hot water at the farthest fixture. Note how long it takes and whether the temperature is consistent.

What Adds Value

• Pressure-balanced or thermostatic shower valves — Stable temperature, no sudden hot/cold swings when someone flushes a toilet.
• WaterSense-rated fixtures — Efficient without sacrificing performance.
• Quality brands — Kohler, Delta, Moen, Toto, etc.
• Good layout — Logical placement, comfortable reach, adequate clearance.

Red Flags

• Cheap builder-grade fixtures — Can indicate a cheaper approach to all the plumbing.
• Mismatched trim — Suggests repeated repairs or DIY work.
• Loose handles or poor mounting — Signs of wear or improper installation.
• Low pressure that can’t be adjusted — Especially concerning with galvanized supply lines.
• Stains, corrosion, or mineral buildup — May indicate hard water issues.

How to Inspect It Yourself

1. Operate every fixture — Turn on every faucet, flush every toilet, run every shower. Note anything that doesn’t work smoothly.
2. Check for leaks — Look under every sink. Open the cabinet and check for moisture, staining, or mold.
3. Test the shower temperature — While showering (or running the shower), have someone flush a toilet. If the temperature swings dramatically, the valve isn’t pressure-balanced.
4. Wiggle handles and spouts — Loose fixtures indicate wear or poor installation.
5. Look at caulking and grout — Deteriorated caulk around tubs and showers can allow water intrusion into walls.
6. Check for mineral deposits — White or greenish buildup on fixtures suggests hard water, which affects all plumbing over time.

What Adds Value

• Modern high-efficiency toilets — Strong flush, lower water usage.
• Dual-flush or pressure-assisted designs — Options for different needs.
• Comfort-height toilets — Easier to use for most adults.

Red Flags

• Constant running — Indicates a failing flapper or fill valve.
• Weak flushing — May be the toilet itself or a drain line issue.
• Floor staining around the base — Possible wax ring failure or flange issues.
• Rocking or movement — The toilet should be solidly mounted.

How to Inspect It Yourself

1. Flush each toilet — Watch the flush strength and listen for complete refill.
2. Listen after flushing — The tank should refill and stop. Continuous running or periodic “phantom flushes” indicate internal problems.
3. Check the base — Look for staining, soft flooring, or discoloration. These suggest a wax ring leak that may have caused subfloor damage.
4. Try to rock it — Gently push on the toilet from different angles. It should be solid. Movement indicates improper mounting or a deteriorated flange.
5. Look behind and around — Check for water stains on nearby walls or flooring.

What Adds Value

• Dedicated shutoff valves — For washing machine, dishwasher, refrigerator ice maker.
• Washing machine drain pan — Especially important on upper floors.
• Properly installed gas appliances — Shutoff valves, sediment traps (drip legs), clean venting.

Red Flags

• No shutoffs — Makes maintenance and emergencies much harder.
• Improvised drain connections — Hoses just stuck into standpipes, missing air gaps.
• Gas lines without proper fittings — Flexible connectors should be rated for the appliance and properly connected.

How to Inspect It Yourself

1. Locate shutoff valves — Check behind the washing machine, under the kitchen sink (for dishwasher), and behind the refrigerator. Each should have its own valve.
2. Look at washing machine connections — Hoses should be braided stainless steel (not rubber), and there should be a drain pan if on an upper floor.
3. Check dishwasher connection — The drain hose should loop up to the countertop level (high loop) or connect through an air gap.
4. Inspect gas connections — If you can see them, look for yellow flexible connectors with proper fittings. There should be a shutoff valve for each gas appliance.

High-Value Design Features

• Short pipe runs — Faster hot water delivery, less waste.
• Recirculation systems — Near-instant hot water at every fixture.
• Zoned plumbing — Better pressure balance throughout the house.
• Sound insulation — Quiet walls and floors when water runs.

These details rarely show up in listings—but they dramatically improve daily life.

How to Evaluate

1. Time the hot water — At each bathroom, time how long until hot water arrives. Under 30 seconds is good. Over a minute means significant water waste.
2. Ask about recirculation — Look for a small pump near the water heater or ask the seller. Recirculation systems are a genuine comfort upgrade.
3. Listen while water runs — Flush toilets and run faucets while standing in other rooms. Excessive noise indicates lack of sound insulation.
4. Test pressure balance — Run the shower while flushing a toilet or running another faucet. Minimal change indicates good system design.

These aren’t deal-breakers, but they affect daily comfort and can inform your offer.

Common Age-Related Concerns

• Outdated pipe materials — Galvanized steel, lead, or polybutylene.
• Undersized drain systems — Older codes allowed smaller pipes.
• Poor venting by modern standards — May cause slow drains or odors.
• Repairs done before current codes — Not necessarily wrong, but worth understanding.

Smart Buyer Moves

Ask the seller or agent:

• Has the plumbing been updated? When?
• Who did the work? (A reputable local plumber is a good sign.)
• Were permits pulled? (Check with the city if uncertain.)
• Are there any known issues?

Request documentation:

• Permits and inspection records
• Receipts from plumbing work
• Home warranty coverage details

Older homes aren’t bad—they just require honest evaluation. A well-maintained 1950s system can outperform a poorly installed new one.

Signs of Quality Work

• Straight, properly supported piping — Professional installers take pride in their work.
• Clean solder joints or fittings — No drips, no discoloration.
• Labeled shutoffs — Someone thought about future maintenance.
• Permits and inspection records — The work was done to code.
• Reputable local contractor names — Ask who did the work.

Warning Signs

• Sloppy routing — Pipes running at odd angles, excessive bends.
• Excessive use of flex lines — Flexible connectors everywhere suggest shortcuts.
• Unlabeled or inaccessible shutoffs — Makes emergencies harder to manage.
• DIY-looking work in critical areas — Water heaters, gas lines, and main connections should look professional.

The Big Ones

• Main sewer line condition — Camera inspection is the only way to know.
• Aging water heater — Factor replacement into your budget if it’s over 10 years old.
• Galvanized supply lines — Eventual full replacement is likely.
• Lack of shutoff valves — Adding them later means opening walls.
• Systems that meet code—but barely — Functional today, problematic tomorrow.

Using Findings in Negotiations

A plumbing inspection can reveal negotiation leverage:

• Sewer line issues — Request repair, replacement, or price reduction.
• Water heater near end-of-life — Ask for credit toward replacement.
• Galvanized pipes — Factor re-piping costs into your offer.
• Code violations — Request correction before closing.

Even if you proceed with the purchase, knowing what you’re inheriting helps you budget for future repairs.