A signed agreement of sale. A buyer with financing lined up. A closing date circled on the calendar for three weeks out. Then, with ten business days to go, a phone call from a plumber: the downspout on the north side of the house has been draining rainwater into the sanitary sewer since sometime before anyone currently living there bought the place, and it has to be disconnected before the municipality will sign off on the sale.
That call is common enough in Mt. Lebanon to have its own ordinance number, its own paperwork, and its own timeline that runs completely separate from a buyer's home inspection. It's called a dye test, and unlike almost everything else in a Pittsburgh-area closing, it's an obligation that falls on the seller alone.
What the Test Actually Checks
Every house has two separate drainage systems that are supposed to stay separate. Sanitary sewers carry wastewater from inside the house, showers, toilets, dishwashers, washing machines. Storm sewers carry water from outside, downspouts, driveway drains, roof runoff. For decades, builders routinely tied the two together anyway, because it was cheaper and nobody was checking. A lot of current homeowners have no idea their downspout is connected to the wrong pipe.
A dye test finds out. A licensed plumber puts powdered dye into a downspout or drain and flushes it through. If that bright green water shows up in a manhole on the sanitary line downstream, the connection is illegal, and it has to be fixed before the property can change hands.
The Fine Print That Actually Matters
Mt. Lebanon's rule lives in Ordinance No. 3099, and the mechanics are specific enough that they're worth writing down before you list, not after you're under contract:
| Requirement | Detail |
|---|---|
| Evidence of Compliance deadline | At least 10 business days before closing |
| Filing fee | $50 |
| Interim Evidence of Compliance (if you need more time) | Must be requested at least 14 business days before closing |
| How long a passed test is valid | Three years from the test date |
| Refinancing | Does not trigger the requirement |
| Who performs the test | A plumber registered and licensed in Allegheny County. The municipality does not do it |
Miss the window and you're not looking at a fine. You're looking at a closing date that quietly stops being real.
A Federal Problem That Landed on Individual Sellers
Mt. Lebanon didn't invent this rule out of municipal caution. The municipality started targeted dye testing back in 1987 in a handful of neighborhoods, including Mission Hills, Central Square, Sunset Hills, Main Entrance Drive, Roycroft Avenue, and Hoodridge Drive. By 1996, roughly 9,000 homes had been tested, and about one in five failed. Every house in the municipality had been tested by the early 2000s, and in 2004 the point-of-sale version of the ordinance became law, tied to a federal mandate on stormwater pollution.
That local rule sits inside a much bigger regional fight. The Allegheny County Sanitary Authority, which treats wastewater for Mt. Lebanon and 82 other municipalities, has been under a federal consent decree since 2008 to stop billions of gallons of untreated sewage from overflowing into the region's rivers during heavy rain. The original target for fixing that was 2026. It's been pushed to 2036, and the roughly $2 billion plan is still mid-construction, with the treatment plant working toward handling 480 million gallons a day by this October and more than 50 miles of municipal sewer lines already transferred to ALCOSAN's ownership to untangle the regional system.
The point of connecting those two facts is not to scare a seller with infrastructure trivia. It's to explain why the dye test isn't a formality that's about to get waived. Every illegal downspout connection is a small contributor to a problem the region is under a court order to solve, and that order runs another decade. Mt. Lebanon's inspectors have no discretion to look the other way on a closing.
What a Failed Test Can Actually Cost
The range is wide, and that's the part sellers underestimate. A single downspout that needs to be rerouted away from the sanitary line might run a few hundred dollars. A more involved correction, particularly in a house with the kind of older plumbing common across Mt. Lebanon's 1920s through 1950s housing stock, can run into the tens of thousands, according to Pittsburgh-area plumbers who handle this work regularly. The variable isn't the size of the house. It's how many drains were tied in wrong decades ago and how much digging it takes to separate them.
That's a cost most sellers never priced into their moving budget, because it doesn't show up until a plumber is standing in the yard with dye and a flashlight.
The Timeline Trap
Here's where it gets genuinely risky, and where it has nothing to do with anyone acting in bad faith. A Pittsburgh real estate attorney who represents buyers and sellers in Allegheny County closings has pointed to a Mt. Lebanon transaction as an example of how procedural delays get misread as contract breaches. In the scenario, a closing missed its date by eleven days, not because of the dye test specifically but because of the same category of routine paperwork, a title backlog and a tax certification that hadn't come back yet. The seller assumed the buyer was in breach, relisted without sending proper notice, and accepted a second offer at a higher price, only to create a legal mess because the first contract was never properly terminated.
The lesson transfers directly. Dye tests, tax certifications, and title searches are not breaches when they run long. They're procedural steps a closing cannot happen without. The clean fix, if a dye test pushes past a target date, is a short written extension signed by both parties, not an assumption that the deal fell apart.
Not Unique to Mt. Lebanon, But Not Optional Here Either
If a buyer's agent mentions the dye test like it's a red flag specific to this address, it isn't. Bethel Park requires the same certification before a sale can close. Upper St. Clair does too. This is a South Hills-wide response to the same regional sewer problem, not a sign that a particular house or block has an issue the rest of the neighborhood doesn't.
How to Get Ahead of It
- Schedule the test before you list, not after you accept an offer. A test result in hand removes a variable from every negotiation that follows.
- Hire a plumber registered and licensed in Allegheny County. The municipality maintains the requirement but doesn't perform the test itself.
- Budget for the possibility of a failed test, not just the $50 filing fee. If your house was built before the 1960s and has never been tested, treat a correction cost as a real line item until you know otherwise.
- Check whether you already have a valid certificate. If the house was tested within the last three years, for a prior sale or otherwise, that certification may still be good.
- Build the 10 business day window into your proposed closing date from the start, and know that 14 business days is your outer limit if you need to request interim relief instead.
A Few Direct Questions
Do I need a dye test if I'm only refinancing? No. The requirement applies to sales and transfers of the property, not refinancing.
What happens if I fail? You can request Interim Evidence of Compliance, which involves posting escrow money to cover the cost of corrective work, but the Inspection Department has to approve whatever fix is made before the sale can close.
Is this something the buyer arranges? No. It's a seller obligation tied to the transfer of the property, and it needs to be handled on the seller's timeline, not folded into the buyer's inspection period.
The dye test is a small line item on a closing checklist that can turn into the single biggest unplanned cost in a Mt. Lebanon sale if it's discovered late. Pricing a home correctly and marketing it well only matters if the closing actually happens on schedule, and that starts with knowing what the municipality requires before a buyer ever walks through the door.
If you're weighing a sale in Mt. Lebanon and want a straight read on your timeline, your numbers, and what a dye test might mean for your specific property, Nate Nieland can walk through it with you. Book an appointment and get ahead of the parts of a Mt. Lebanon sale that don't show up on a listing sheet.
