Key takeaways
- A building's supply is a network of risers, horizontal mains, branches and often a hot-water recirculation loop, each with its own failure pattern.
- Interior leaks are located with isolation, acoustic, thermal and moisture methods without closing the building.
- Isolation valves that exist and work are the single biggest factor in how disruptive a repair is.
- Repeated interior leaks on the same riser or main are a replacement item for the reserve study.
How water moves through the building
The service enters at the point of entry, usually a mechanical room, through a backflow assembly and a main valve. From there a trunk feeds horizontal mains in the ceilings or crawlspace and vertical risers up through chases, with branches into each unit or tenant space. Larger buildings add a hot-water recirculation loop so hot water arrives quickly at distant fixtures. Every one of those elements has valves, or should, and the condition of those valves decides how a repair goes.
Where they fail
- Risers: galvanized rusts through at threads; copper pinholes at hangers and slab penetrations.
- Horizontal mains in ceilings: copper at hangers and dissimilar-metal contacts; CPVC at joints as it ages.
- Branches into units: polybutylene fittings in 1980s and 90s multi-family; copper at nail plates.
- Recirculation loops: erosion at elbows and tees near the pump; fittings at the pump itself.
- Mechanical rooms: unions, valves, backflow assemblies and water heater connections.
- Slabs: copper in contact with concrete on slab-on-grade buildings.
How interior leaks are found in an occupied building
The loss is confirmed at the meter with the exterior line isolated. Risers, branches and the loop are isolated where valves exist, with gauges on each. Acoustic sensors listen along the traced mains; a thermal camera reads a hot-loop leak through drywall or slab; moisture meters trace a stain back to its source. The mark goes on one ceiling tile or wall, and the opening and repair are scheduled around the tenant, often after hours.
Valves are everything
A building where every riser and branch can be isolated has repairs that affect one floor for an hour. A building where the only working valve is the main has repairs that shut down everyone. Adding or replacing isolation valves is often the highest-value improvement an older building can make, and it's usually done as part of the first repair rather than waiting for a replacement.
When it's a system, not a leak
Three interior leaks in two years on the same riser or main is a system at the end of its life. A phased repipe, by floor, wing or stack, with new isolation valves everywhere, is a reserve study item rather than an emergency. The assessment that follows a repair, with the material, age and failure history documented, is what the board needs to plan it.
Written by the crew at 360 Leak Finders
We locate, excavate and repair buried water lines and exterior drains across Kitsap County, 24 hours a day. If this guide raised a question about your property, call (206) 354-9906.