You’ve found the "perfect" house. The kitchen is updated, the backyard is huge, and the price is right.

But before you fall in love, look down. Then look under the sink. Then flush the toilet.

Plumbing issues are the #1 hidden cost for new homeowners. A fresh coat of paint can hide water damage, and a beautiful lawn can hide a collapsed sewer line. If you don't check these systems before you close, you could be inheriting a $15,000 repair bill on day one.

In 2026, home inspections are more critical than ever, but standard home inspectors often miss the deep plumbing issues. Here is the ultimate plumbing checklist to take with you to your next viewing.

1. The "Big Ticket" Items (Check These First)

Forget the leaky faucet for a second. These are the expensive, deal-breaking issues that should make you reconsider the offer or demand a massive price reduction.

A. The Sewer Line (The $10k Risk) You cannot see this, but it is the most dangerous pipe on the property.

The Risk: Roots from that beautiful oak tree in the front yard may have crushed the pipe, or it could be made of "Orangeburg" (tar paper) or cast iron that has rotted away.
The Test: A standard home inspector will not check this. You must hire a plumber to perform a Sewer Camera Inspection. If the line is collapsed, the repair often requires digging up the entire yard or driveway.

B. The Water Heater

The Check: Find the manufacturer’s sticker. Look for the serial number—the first two numbers usually indicate the year it was built.
The Rule: If it is a tank unit over 10 years old, it is living on borrowed time. Budget $1,500–$3,000 for a replacement immediately.
Red Flag: Rust at the bottom of the tank means a leak is imminent.

C. Pipe Material (The "Uninsurable" Pipes)

Polybutylene: If the house was built between 1978 and 1995, look for grey plastic pipes. These are notorious for bursting and many insurance companies will not cover homes that have them.
Galvanized Steel: In homes built before 1960, look for silver/grey metal pipes. These rust from the inside out, causing low water pressure and eventual failure.
The Fix: If you see these, you are looking at a Whole House Repipe.

2. The Room-by-Room Walkthrough

Once you’ve cleared the major hurdles, use this checklist for the specific fixtures.

The Bathroom

The "Toilet Rock": Straddle the toilet and try to rock it side to side. If it moves, the wax ring is likely broken, and there may be a slow leak rotting the floor underneath.
Soft Floors: Step firmly around the tub and toilet. If the floor feels "spongy," you have subsurface water damage.
Shower Pressure: Turn on the shower. Does the pressure drop when you flush the toilet? This indicates older, undersized piping or a main line restriction.

The Kitchen

Under the Sink: Use your flashlight. Don't just look for water; look for water stains or warped wood at the bottom of the cabinet. This indicates a chronic leak that the seller may have wiped up right before you arrived.
The Disposal: Turn it on. A loud "crunching" or "humming" sound means it’s seized or broken.

The Yard

The "Soggy Spot": Walk the yard between the house and the street. If you find a patch of grass that is greener than the rest or squishy when it hasn't rained, you likely have a main water line leak.
The Hose Bibs: Turn on the outdoor faucets. If water sprays out from the handle stem, the frost-free valve has burst (common in colder climates).

3. The Water Meter Test (The "Secret Weapon")

This is a pro trick you can do yourself during the viewing.

Turn off all water inside the house (faucets, dishwasher, washing machine).
Go to the water meter box near the street.
Look for the "leak indicator" (a small triangle or star) or watch the digital number.
If it is moving: Water is leaving the meter but not being used inside. You have a hidden leak—possibly a Slab Leak.

Conclusion: When to Call a Pro

A general home inspector is a generalist. They check the roof, electric, and structure. They are not plumbers.

If you find any red flags on this list—especially regarding the sewer line or pipe materials—do not close on the house without a specialized plumbing inspection. Spending $300 now could save you $30,000 later.

Need a certified inspection before you buy? Find a Plumber on TruePlumber