Quick questions to ask neighbors
A two-minute check up and down the street often answers the main-or-lateral question before any plumber arrives.
- Is anything coming up your basement floor drain or lowest toilet right now?
- Did your drains start running slow or gurgling today?
- Are you on the same side of the street, or does your line run to the alley?
- Has anyone already called the sewer provider, and what reference were they given?
- Did anyone see crews working on the main or a nearby manhole recently?
How a main blockage behaves
A sanitary sewer main collects the laterals from a row of houses and slopes toward a larger trunk line. If grease, roots, debris or a collapse blocks it, flow backs up behind the obstruction. The houses whose laterals join the main upstream of the blockage are all at risk, and whichever homes have the lowest drain openings, usually those with basements, overflow first. Homes on slab foundations or on higher lots may notice nothing more than slow drains.
Because the pattern depends on elevation, it is common for one house with a deep basement to take most of the damage while the neighbor with a crawlspace is untouched. That does not mean the problem is in the flooded home's lateral. It is worth asking which side of the street the main runs on and whether neighbors share a stretch of it.
What to do in order
- Stop water use.Ask everyone in the house, and if it is a main issue, your neighbors, to stop flushing and running water. Every gallon used upstream adds to the overflow.
- Call the provider on your bill.In most of Thornton that is the city utilities department. Use the emergency or after-hours number on the bill or the city website. Note the time and any reference number.
- Photograph the timing.Take time-stamped photos of the floor drain, the water level and any neighbors' visible issues. This helps show the event started outside your lateral.
- Have a plumber confirm your line.If the provider clears the main and your drains recover, a plumber may not be needed for the blockage itself, but ask for an opinion if anything still drains slowly.
- Start contaminated-water cleanup.The cleanup clock starts whether or not the blockage was yours. Category 3 water should not sit on carpet and drywall while responsibility is sorted out.
Records that help after a main backup
| Record | Why it matters | Who has it |
|---|---|---|
| Time of your report to the provider | Shows prompt notice | You, and the provider's log |
| Provider work order or crew notes | May state where the blockage was found | Request from the provider |
| Plumber invoice or note | Can record that your lateral was clear | Your plumber |
| Neighbor statements | Shows multiple homes were affected | Neighbors; a short written note is enough |
| Cleanup scope and photos | Documents what was removed and why | The cleanup contractor and you |
Common questions
Why did my house flood when the neighbor's did not?
Usually elevation. The home with the lowest open drain overflows first. A deeper basement or a lower lot makes your floor drain the relief point for the whole run of pipe.
General information for Thornton, not a quote or professional advice. In an emergency, call 911.