Short definition

A pre-purchase plumbing inspection is a dedicated plumbing scope of a home before closing — deeper than a general home inspection’s plumbing section. In WA pre-1970 stock, it routinely includes a recorded sewer-camera scope of the side sewer. Total typical Seattle / Tacoma cost in 2026 is $700–$1,500 with the scope. It’s the cheapest insurance against a $30,000 surprise.

What it is

A general home inspection ($400–$700) covers many systems briefly. A dedicated pre-purchase plumbing inspection ($300–$500) goes deeper on plumbing alone. In Washington, the standard add-on is a sewer-camera scope of the side sewer — $250–$550 in Seattle and Tacoma — because the homeowner owns the side sewer all the way to the public main. See side sewer for the ownership rule.

Always included

  • Visual walkthrough of every accessible pipe (basement, crawlspace, attic).
  • Fixture-by-fixture function test (faucets, toilets, tubs, showers, dishwasher, washer hookups).
  • Water heater inspection (age, anode rod, corrosion, T&P relief, earthquake straps).
  • Visible shut-off verification (main, branch, supply stops).
  • Static water pressure measurement at hose bib.
  • Drain function test at every fixture.
  • Visible supply pipe material identification (galvanized, copper, PEX, lead).

WA-standard add-ons

  • Sewer scope inspection ($250–$550): camera through the side sewer, identifies Orangeburg collapse, clay-tile failure, root intrusion, and bellies. Near-mandatory for pre-1970 PNW homes.
  • Lead in water test ($25–$50 lab fee): pre-1986 homes especially, paired with Cedar/Tolt soft acidic water.
  • Backflow preventer test (where applicable, e.g., irrigation).
  • Pressure-reducing valve check.

Sometimes included

  • Whole-house thermal imaging.
  • Sewer ejector pump test (basement bathroom).
  • Sump pump test.
  • Septic tank inspection (separate trade — WA-certified septic specialist).

Why it matters to a homeowner

The PNW math: a $250–$550 sewer scope is insurance against a $8,000–$30,000 side-sewer replacement that you discover six months after closing. Five things to lean on:

1. Pre-1970 stock + side-sewer ownership = scope is not optional

Seattle (Capitol Hill, Wallingford, Ballard, older Queen Anne), Tacoma (Hilltop, Old Town, North End), and Spokane (Browne’s Addition) all have substantial Orangeburg, clay-tile, or fragile cast-iron side sewers from before modern PVC. Buyer inherits everything at closing. See side sewer.

2. Demand the recorded sewer-scope video

Refusing to share a recorded scope is unreasonable in 2026 — every contemporary scope camera records. The video is your evidence for second opinions and price negotiations. If the inspector won’t share it, treat that as a red flag and hire someone else.

3. Don’t waive the inspection contingency

The hot WA real estate market 2018–2022 saw widespread inspection waivers. Many backfired in pre-1970 home purchases — buyers discovered Orangeburg or galvanized supply post-close with no recourse. Always inspect, especially in PNW pre-1970 stock. The market lever is leverage on price, not on safety.

4. Test for lead in pre-1986 homes

Pre-1986 lead solder plus Cedar/Tolt soft acidic water can elevate lead in stagnant first-draw samples. Pre-1940 lead service lines exist in pockets of Tacoma (Hilltop, Old Town) and Seattle. A $25–$50 lab fee gets you the answer.

5. Verify the inspector isn’t tied to the repair plumber

Some inspectors take referral fees from the plumbers they recommend for repairs. Ask: “Are you affiliated with any plumbing companies?” before hiring. Get repair quotes from three independent plumbers, separate from the inspector’s recommendation.

Cost data — Seattle / Tacoma 2026

  • General home inspection: $400–$700 (plumbing as a brief section).
  • Dedicated plumbing inspection: $300–$500.
  • Sewer scope add-on: $250–$550.
  • Water lead test: $25–$50.
  • Pre-purchase total typical PNW: $700–$1,500 with general + sewer scope.

Common scenarios

  • Pre-1970 Seattle home, $1M+: general inspection + dedicated plumbing + sewer scope = $1,000–$1,500. Best money spent in the transaction.
  • New construction (2010+): general inspection sufficient; sewer scope optional (some new builds have undocumented Orangeburg sections from pre-existing cleanout points).
  • Tacoma pre-1940 home: add lead-in-water test plus sewer scope to general inspection.
  • Spokane / Eastern WA: hard-water profile means water-heater scaling history matters. Inspector should report water-heater age and condition specifically.
  • Manufactured home: WA L&I separately licenses manufactured-home installers. Plumbing inspection is a different specialty.

Washington note

Side-sewer ownership in Seattle and Tacoma runs from the house all the way to the public main — usually a curb cleanout, sometimes the street centerline. Buyer inherits whatever is there at closing. SPU and Tacoma Permits each maintain their own registered side-sewer contractor lists separate from the L&I plumbing contractor registration.

For pre-1986 homes, pair the lead-in-water test with acidic water corrosion and the Cedar/Tolt soft acidic water profile to interpret results. A first-draw lead reading from a tap that’s been sitting overnight tells a different story than a flushed sample.