Old house plumbing in Seattle: what to watch and when to replace

How old are Seattle homes?

Older than in most American cities. Census Bureau survey data for 2020 to 2024 put the median year built for Seattle housing at 1976, and about 23 percent of all homes were built in 1939 or earlier. Another 7 percent date from the 1940s and 8 percent from the 1950s (ACS table B25034 via Census Reporter). A house that old has usually had its plumbing changed in pieces, so the pipes in the basement can be a mix of decades and materials.

What should you look for in an old Seattle house?

Area	What to check	Why it matters
Side sewer	Camera inspection of the pipe from the house to the main	SPU says many Seattle side sewers are concrete, and eroding concrete is a common and critical defect
Supply piping and fixtures	Pipe material where the line enters the house; age of faucets and valves	Older brass fixtures and lead solder can leach lead
Main shut-off valve	Find it, and confirm it turns	You need it in a leak; SPU recommends installing one if the home has none
Pipes in crawlspaces and on exterior walls	Insulation and drafts from foundation vents	SPU says pipes exposed to drafts from open vents are most at risk of freezing or splitting
Past work	Permit history for any repipe, water heater or sewer repair	Unpermitted work may need to be legalized later

What happens to old side sewers?

Seattle Public Utilities' side sewer defects page explains the main problems. Many side sewers in Seattle are concrete pipe. As the cement inside erodes, the aggregate (rocks) becomes exposed. Minor exposed aggregate has little effect and should be reinspected in three to five years; a bumpy, porous surface means structural stability is decreasing and repairs should be planned within one to two years; exposed aggregate with holes means the pipe has reached full structural failure and should be replaced as soon as it is found.

Roots are the other big issue. SPU says older concrete and clay side sewers that were not built with watertight joints are especially at risk, and that a tree's roots can grow up to two times the length of the tree's height. Property owners are responsible for removing roots up to and within the connection to the sewer main. Our side sewer inspection guide explains how to read a camera report, and our repair options guide covers what comes next.

Is there lead in old Seattle plumbing?

Seattle's source water does not contain lead, according to SPU's lead in water page. The risk is inside the house: lead can leach from lead-based solder and brass fixtures. The EPA's lead in drinking water overview says lead pipes are more likely in homes built before 1986, and that among homes without lead service lines the most common problem is brass or chrome-plated brass faucets and plumbing with lead solder. Federal law now caps lead at a weighted average of 0.25 percent for pipes, fittings and fixtures and 0.2 percent for solder and flux.

SPU's advice for older homes:

• If water has sat in the pipes for over 6 hours, run the tap for 2 minutes before drinking.
• Use only cold water for drinking, cooking and baby formula; lead dissolves more quickly in hot water.
• Choose low-lead or no-lead fixtures when you replace them.
• To test, contact a lab certified by the Washington State Department of Ecology. SPU says analysis costs range from $25 to $50.

When should you repipe instead of repairing?

There is no single age at which pipes must be replaced. Repeated pinhole leaks, low pressure at several fixtures, discolored water, or a mix of patched materials are reasons to get a repipe quote alongside a repair quote. In Seattle, a repipe needs a plumbing permit from Public Health Seattle and King County. Its 2026 fee schedule adds a supplemental fee for repipe projects based on the expected number of inspections, on top of $137 plus $27 per fixture. Our cost guide lists typical repair and replacement prices.

How do you protect old pipes in winter?

SPU's frozen pipes page recommends insulating pipes in attics, basements and garages, closing or blocking foundation vents in cold weather, draining outdoor faucets, keeping the thermostat at 55 degrees or higher, and letting one indoor faucet drip during severe cold. If a pipe breaks, close the main shut-off valve immediately. SPU's shut-off instructions say customers should generally use their home valve; only meters with a top shut-off valve can be closed by the customer, and SPU customers can call (206) 386-1800 for help shutting off at the meter.

How do you hire for an old house?

Ask each plumber how often they work on homes of your age and which materials they expect to find, and ask for camera video or photos of anything they recommend replacing. Check the company in the L&I Verify tool. Our hiring guide covers the full checklist.

How does this site fit in?

We are an independent guide operated by SWKM GmbH, not a contractor, and we do not perform plumbing work. If you want help, email us your neighborhood or ZIP code, the problem and a few photos. We reply by email with next steps and, where we know a licensed contractor for your area, an introduction. Run the checks on this page on anyone you hire, including anyone we mention.