A leaking roof drain almost always fails in one of three places: the clamping ring that squeezes the roof membrane against the drain bowl, the drain bowl itself, or the joint where the bowl meets the pipe below the roof deck. A clogged strainer makes all three worse, because water that can’t get down the drain sits on the roof and works its way into every weak seal. This guide walks through how a roof drain is built, how to find which part is leaking, the five checks you can safely do yourself, and when the repair belongs to a roofer.
It is written by the team at Crafted Exterior Services, a Martinsburg roofing contractor that works on commercial roofs and residential flat roofs across Berkeley County and the Eastern Panhandle.
How a Roof Drain Is Built
Every internal roof drain has the same four parts, and knowing them makes it much easier to describe a leak to a contractor:
- Dome or strainer: the cage on top that keeps leaves and debris out of the pipe.
- Clamping ring: a bolted ring that presses the roof membrane down onto the drain bowl to make a watertight seal.
- Bowl (or body): the funnel set into the roof deck, usually cast iron on older buildings and PVC or aluminum on newer ones.
- Hub or pipe connection: where the bowl joins the drain pipe that carries water down through the building.
Signs Your Roof Drain Is Leaking or Failing
- A water stain or drip on the ceiling directly below the drain, often worst during heavy rain.
- Water still standing around the drain two days after the rain stops. A common roofing rule of thumb treats water that lingers past 48 hours as ponding that needs attention.
- Loose, rusted or missing bolts on the clamping ring.
- Cracks, blisters or a lifted edge in the membrane around the bowl.
- Gurgling, slow draining or water backing up out of the strainer.
Why Roof Drains Fail in Martinsburg
Martinsburg sits in the path of slow, heavy summer storms. The National Weather Service office in Sterling, Virginia, which covers Berkeley County, regularly issues flash flood warnings for Martinsburg when storms stall over the Eastern Panhandle and drop inches of rain in a few hours. A flat roof has to move all of that water through a handful of drains, so one clogged strainer can turn a storm into a leak.
Fall is the other risk season. Leaf drop from the trees around older neighborhoods fills strainers fast, and when freeze-thaw cycles arrive, water trapped around a drain freezes, expands and pries at the membrane seal. The older commercial buildings in the Downtown Martinsburg Historic District, many of them low-slope roofs behind parapet walls, rely entirely on internal drains and scuppers, which makes drain maintenance there especially important.
5 Steps to Find and Fix a Leaking Roof Drain
Only do these checks if you can reach the roof safely, the surface is dry, and there is no storm in the forecast. Stay well back from roof edges and skylights.
- Clear the strainer and drain opening. Lift off the dome, remove leaves and debris by hand, and run water from a garden hose into the drain. If it backs up, the clog is in the pipe and a plumber with a drain snake or camera is the right call.
- Check the clamping ring bolts. Missing or loose bolts let water slip between the membrane and the bowl. Snug loose bolts evenly by hand. Do not overtighten, which can crack an old cast iron bowl.
- Inspect the membrane around the bowl. Look for splits, blisters, lifted edges or old patches peeling away. Membrane repairs need the matching material: TPO is heat-welded and EPDM uses seam tape and primer, so a hardware-store sealant smeared over the gap usually fails within a season.
- Look for cracks in the bowl. Cast iron bowls on older buildings can crack from freezing water or a hard impact. A cracked bowl is not a sealant repair; it needs a new bowl or a retrofit drain.
- Test it and watch below. Run the hose into the drain for several minutes while someone watches the ceiling and any visible pipe underneath. A leak that shows up only when water goes down the pipe points to the hub connection, not the roof.
Retrofit Drains: The Fix for a Cracked Drain Bowl
When the drain bowl is cracked or corroded, replacing it can mean opening the roof deck and the ceiling below. A retrofit drain avoids most of that. It is a new drain with a sleeve that slides down inside the existing pipe and seals against it, while a new flange is tied into the roof membrane. It is usually the fastest, least disruptive repair for an aging cast iron drain, and it is often done alongside a TPO or EPDM repair or a roof coating project.
Who Fixes a Roof Drain: Roofer or Plumber?
It depends on where the leak is. The pipe inside the building belongs to the plumbing system, so a clog or a leak below the roof deck is a plumber’s job. Everything at the roof surface, including the membrane seal, the clamping ring and a retrofit drain tied into the roofing, is roofing work. If you are not sure which you have, a roofer can find the source in one visit and tell you whether you need a plumber too.
When to Call Crafted Exterior Services
Call us if water is coming into the building, if the membrane around the drain is torn, or if the bowl is cracked. Our crews handle commercial roof repair and roof leak repair across Martinsburg and Berkeley County, and for active leaks during a storm we offer emergency roof repair. A drain leak caught early is usually a small repair. Left alone, it soaks the insulation and decking around the drain, and that turns a repair into a section of new roof.
Ready to find out what’s causing your leak? Contact our team for a free roof inspection and a written estimate.
Crafted Exterior Services
Address: 85 Lynnhaven Dr, Suite E, Martinsburg, WV 25404
Phone Number: (681) 283-8257
Google Maps: Find Us Here
Business Hours: Monday to Friday, 8:00 AM to 5:00 PM. Saturday and Sunday: Closed
Frequently Asked Questions
How do you fix a leaking roof drain?
Clear the strainer, tighten any loose clamping ring bolts, and inspect the membrane and drain bowl for damage. A torn membrane needs a patch in matching material, and a cracked bowl needs a new bowl or a retrofit drain. If water only leaks while it runs down the pipe, the problem is the pipe connection below the roof.
What are the drains on a flat roof called?
They are called internal roof drains or interior drains. Water can also leave a flat roof through scuppers, which are openings in the parapet wall, and through gutters along the roof edge.
Do plumbers or roofers repair roof drains?
Both, depending on the leak. Plumbers handle the drain pipe inside the building. Roofers handle the drain bowl, clamping ring and membrane seal at the roof surface.
What is a roof drain retrofit?
A retrofit drain is a replacement drain with a sleeve that fits inside the existing drain pipe. It replaces a cracked or corroded drain bowl without tearing out the old bowl or opening the ceiling below.
Why is there water dripping from my roof drain pipe inside the building?
Water dripping from the pipe itself usually means a loose or failed joint where the drain bowl meets the pipe, or a cracked pipe. Water dripping from the ceiling around the pipe more often means the roof membrane seal at the drain has failed.
How often should flat roof drains be cleaned?
At least twice a year, in late spring and after the fall leaves drop, plus after any major storm. Buildings surrounded by mature trees may need more frequent checks.