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Water on the Sill After Rain: Weep Holes or an Installation Leak?
I’m trying to sort out a drainage issue on a replacement window before I start removing caulk. It’s a vinyl, double-hung window that’s roughly 8 years old. After ordinary rain, the lower interior sill is sometimes damp, but it’s more noticeable when the rain is wind-driven. The water seems to collect along the inside track rather than running down the wall or soaking the drywall.
The exterior sill has small weep openings, but I can’t tell whether they’re clear. One section looks like it may have dirt or old sealant in it, and I’m not sure whether the openings were accidentally covered when the window was installed. I also don’t know if the water is supposed to be visible in the track briefly while the weep system drains.
Before calling the installer, I’m planning to:
- Check the exterior weep openings in good light and gently clear only loose debris with a soft brush or a plastic pick.
- Avoid drilling, enlarging the openings, or spraying high-pressure water into them.
- Pour a small amount of clean water into the exterior drainage channel, if accessible, and watch whether it exits outside rather than backing up indoors.
- Inspect after the next rain to see whether the problem occurs only with wind-driven rain or also during calm rainfall.
For those familiar with replacement windows, what signs distinguish a blocked weep system from water getting around the window during installation? Also, if the exterior weep openings are visible but recently caulked over, should that caulk be removed, or is it better to stop and have the installer inspect it?
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5 replies
A little water briefly visible in the lower track can be normal, especially during wind-driven rain, because that’s the collection path before the weeps drain it outside. It shouldn’t remain pooled, rise high enough to cross the inner track, or leave the interior sill damp after drainage.
If the small water test backs up or drains very slowly, a blocked weep is likely. If the weeps flow freely but rain still gets past the inner track, I’d suspect an installation or flashing issue rather than removing more caulk. Avoid sealing the exterior drainage openings, since that can trap water inside the frame.
For the small water test, should the water go only into the exterior sill’s drainage channel, rather than into the sash track? Pouring it into the track might test a separate path and make a blocked or slow weep system look normal, or vice versa. I’d also keep the amount small enough to observe whether it exits through the exterior openings without reaching the inner track.
Freely flowing weeps wouldn’t rule out an installation or sash problem. Wind-driven rain can get past a failed sash seal, a misaligned meeting rail, or a gap at the corner while the sill’s drainage path is still completely open. In that case, the test water exits normally, but rain is entering from a different path.
After confirming the weeps drain, I’d check whether the dampness starts near a sash corner or along the meeting rail, rather than only at the outer sill. Also look for a damaged or compressed weather seal. I’d avoid adding exterior caulk until that’s sorted, since it could block the intended drainage route and make the source harder to identify.
The location of the dampness after different types of rain should help separate those possibilities. After calm rain versus wind-driven rain, is the water concentrated at one sash corner or along the meeting rail? That pattern would point more toward a damaged seal or sash alignment issue. If water instead rises from the sill channel and spreads along the track, the drainage path may be overwhelmed or restricted, even if the exterior weep openings do release some water.
Freely flowing weeps only show that water in the exterior channel can escape. They don’t establish that the sill pan or flashing is correctly tied into the surrounding wall.
A damp interior sill also warrants attention to the perimeter, especially the lower corners and side jambs, where water can enter around the replacement frame. Don’t add caulk or remove existing sealant blindly; persistent leakage with an open drainage path is a good reason to have the installation and surrounding trim inspected.