What to Do When Your Kitchen Remodel Uncovers Plumbing Problems

What Is Behind That Wall

Your kitchen remodel is underway. The cabinets are out, the countertops are removed, and the demolition crew is taking down the drywall. Then your contractor calls you over and points at the exposed wall cavity. Instead of clean, functional plumbing, you see pipes coated in rust, corroded fittings, and a drain line that looks like it belongs in a museum.

Welcome to one of the most common surprises in Bay Area kitchen remodeling. Plumbing problems hide behind walls for decades, performing just well enough that you never notice, until someone opens the wall and reveals the full picture.

Why Kitchen Remodels Expose Plumbing Issues

Galvanized Steel Pipes

If your Bay Area home was built before 1970, there is a strong chance the supply pipes are galvanized steel. These pipes were the industry standard for decades, but they have a significant flaw: they corrode from the inside out.

Over 50 to 70 years, mineral deposits and rust build up inside galvanized pipes, gradually reducing the interior diameter. A pipe that started with a 3/4-inch opening may now have an effective diameter of 1/4 inch or less. This restricts water flow, reduces pressure, and produces discolored water.

From the outside, galvanized pipes may look fine. From the inside, they are often nearly blocked. You only discover this when you cut into one during a remodel.

Cast Iron Drain Pipes

Cast iron was the standard material for drain lines in homes built before the 1970s. While cast iron is durable, it eventually corrodes, develops cracks, and accumulates heavy buildup that restricts drainage. In the Bay Area’s moist environment, cast iron pipes in crawl spaces and under floors can deteriorate faster due to condensation and soil contact.

Common cast iron problems found during kitchen remodels include:

• Cracked or split pipe sections
• Heavy rust and scale buildup restricting flow
• Failed joints leaking into the subfloor or crawl space
• Bellied (sagging) sections that trap waste and cause slow drains

Undersized Supply Lines

Older homes were plumbed for the fixtures and appliances of their era. A 1960s kitchen might have had a single sink and a dishwasher. Today’s kitchens often include a primary sink, a prep sink, a dishwasher, a pot filler, an ice maker, and an instant hot water dispenser. The original supply lines were not sized for this level of demand.

Code Compliance Issues

Plumbing codes have evolved significantly over the decades. Common code issues found behind kitchen walls include:

• Missing or improperly sized vent pipes
• S-traps (replaced by P-traps in current code)
• Drain pipes with incorrect slope
• Mixed materials connected without proper transition fittings
• Missing clean-out access points

While these may not all require immediate correction during a cosmetic remodel, any work that touches the plumbing system will need to meet current code standards for the portions being modified.

What to Do Step by Step

Step 1: Document the Conditions

Before anything else, take detailed photos and video of the exposed plumbing. Document the pipe materials, visible corrosion, connections, and any evidence of leaks. This documentation serves multiple purposes: it helps your plumber assess the situation, supports any insurance claims, and provides a record for future reference.

Step 2: Get a Professional Plumbing Assessment

Bring in a licensed plumber to evaluate the exposed plumbing and, if possible, inspect the accessible plumbing throughout the home. The plumber should provide:

• An assessment of pipe condition and remaining useful life
• Identification of materials and sizes
• Recommendations for repair vs. replacement
• A scope of work for the recommended approach
• A cost estimate

If the plumber can only see the kitchen plumbing (because other walls are still closed), ask them to scope the main drain line with a camera ($150-$400). This reveals the condition of the larger drain system that connects to the sewer.

Step 3: Decide Between Kitchen-Only and Whole-House Re-piping

This is one of the most important decisions you will make during the project. Here are the considerations:

Kitchen-only re-piping makes sense when:

• The rest of the home’s plumbing is in good condition
• The home was built after 1970 with copper supply lines that are still sound
• Budget constraints do not allow for full re-piping
• You are not planning any other remodels in the near future

Whole-house re-piping makes sense when:

• Galvanized supply pipes are found in the kitchen (they are almost certainly throughout the house)
• You have noticed low water pressure, discolored water, or slow drains in other areas
• You are planning bathroom remodels or other renovations in the coming years
• The home is 50+ years old and has never been re-piped
• The incremental cost of adding whole-house scope during a kitchen remodel is significantly less than doing it as a standalone project

Step 4: Choose Your Pipe Material

For supply lines, you have two primary options:

Copper

• Proven track record spanning 50+ years
• Higher material and labor costs ($5,000-$10,000 for a kitchen)
• Requires soldered joints (more labor-intensive)
• Excellent durability and resale perception
• Rigid pipe that requires more fittings and connections

PEX (Cross-Linked Polyethylene)

• Industry standard since the 2010s
• Lower material and labor costs ($3,000-$7,000 for a kitchen)
• Flexible tubing that reduces the number of fittings
• Resistance to freezing and bursting
• Faster installation
• Approved by all California building departments

For drain lines, ABS (acrylonitrile butadiene styrene) is the standard material in California. It is lightweight, easy to work with, and highly durable. Cast iron replacement with ABS is straightforward and adds minimal cost to the project.

Step 5: Adjust Your Project Scope and Timeline

Once you have a clear understanding of the plumbing work needed, update your project scope with your contractor. Key adjustments include:

• Budget: Add the plumbing costs to your project total. This is where your contingency fund comes in.
• Timeline: Kitchen re-piping adds 3-5 days; whole-house re-piping adds 5-10 days.
• Sequencing: Plumbing rough-in must happen before insulation and drywall. If the plumbing scope increases, the drywall phase shifts accordingly.
• Permits: Additional plumbing work may require a separate plumbing permit or an addendum to your existing permit.

Cost Breakdown

Scope	Copper	PEX
Kitchen supply lines only	$3,000-$5,000	$2,000-$3,500
Kitchen supply + drains	$5,000-$10,000	$3,000-$7,000
Whole-house supply re-pipe	$10,000-$18,000	$8,000-$12,000
Whole-house supply + drains	$15,000-$25,000	$10,000-$18,000
Main sewer line replacement	$5,000-$15,000	$5,000-$15,000

All pricing is approximate, reflects 2026 Bay Area market conditions, and is subject to change. Every project is unique. Final costs are determined on a project-by-project basis during our design phase.

How to Prevent Plumbing Surprises

Pre-Remodel Plumbing Inspection

Before starting your kitchen remodel, invest in a plumbing inspection. A licensed plumber can evaluate accessible pipes in the crawl space, attic, and utility areas. A camera scope of the main drain line adds another layer of insight. Total cost: $250-$600. This small investment can reveal conditions that inform your budget before demolition begins.

Know Your Home’s Plumbing History

If you have the original building plans, they will show the plumbing layout and materials. Your local building department may also have records of any permitted plumbing work done over the years. Knowing whether the home has ever been partially re-piped helps predict what you will find behind the walls.

Build Contingency Into Your Budget

For any kitchen remodel in a Bay Area home built before 1980, assume that plumbing costs will exceed the initial estimate. A 15-20% contingency fund is standard practice and exists specifically for discoveries like corroded pipes and failing drains.

When to Call a Professional

Call a licensed plumber immediately if you discover:

• Corroded or rusted pipe material exposed during demolition
• Active leaks or evidence of past leaks (water stains, mold, rot)
• Standing water in the crawl space beneath the kitchen
• Unusual pipe materials (lead, polybutylene, or unknown plastics)
• A strong sewer odor when drains are exposed

If structural damage from leaking pipes is evident (rotted subfloor, damaged joists), also contact a structural engineer.

Why Custom Home Design and Build

Plumbing problems behind kitchen walls are familiar territory for our team. We have remodeled hundreds of kitchens in Bay Area homes ranging from the 1920s to the 1990s, and we know what to expect when walls come down.

Our Phase 1 (Design) process includes a pre-construction assessment that evaluates visible plumbing conditions and accounts for the likelihood of hidden issues based on the home’s age and construction type. We build appropriate contingency into our project budgets so that plumbing discoveries do not derail your timeline or break your budget.

When plumbing issues are found during demolition, our team moves quickly. Our project manager coordinates with the plumbing crew, adjusts the construction schedule, and communicates the impact to you clearly and promptly. Because we manage the entire project, there is no delay while you try to find a separate plumber, get a quote, and coordinate access.

Get in touch to start planning your kitchen remodel with a team that plans for the unexpected.