---
title: How to Clean the Inside of uPVC Window Frames
description: How to clean UPVC window frames inside, including the rebates, drainage channels and seals, to stop leaks and keep windows working, for York homes in 2026.
---

[Windows & Doors Advice & Guides | SM Windows & Doors York](https://smwindowsanddoors.co.uk/blog)

# [How to Clean the Inside of uPVC Window Frames](https://smwindowsanddoors.co.uk/blog/sm-windows-doors-blog/how-to-clean-the-inside-of-upvc-window-frames)

 Written by [SM Windows & Doors](https://smwindowsanddoors.co.uk/blog/author/sm-windows-doors) | Oct 28, 2026, 9:30:00 AM

Most people wipe the glass and the visible frame, then stop. But knowing how to clean uPVC window frames inside, meaning the rebates, drainage channels and seals hidden when the window is shut, is what keeps them working smoothly and stops leaks and draughts creeping in. It takes ten minutes per window and saves a lot of bother later.

## Why the inside of the frame matters

When you open a uPVC window you will see grooves, channels and rubber seals that you never notice when it is closed. These do real work. The seals keep out wind and rain, and the drainage channels carry away any water that gets in so it flows outside rather than pooling on your sill or running indoors.

Over time these fill up with dust, dead flies, cobwebs and grime, especially in York's damp autumns. Blocked drainage channels are one of the most common causes of a window that leaks or streams with condensation, and dirty seals harden and stop sealing. A quick regular clean prevents both.

## What you will need

You do not need anything special:

- Warm water with a little washing-up liquid
- A soft cloth and an old toothbrush or small brush
- A vacuum with a nozzle attachment
- A dry cloth
- A little petroleum jelly or silicone-based lubricant for the seals

Avoid bleach, abrasive scouring pads and harsh solvents. They can dull the uPVC, mark it or damage the rubber seals.

## Step by step

### 1. Open the window fully and vacuum

Open the window right up so you can reach the frame all the way round. Run the vacuum nozzle along the grooves and channels to lift out the loose dust, dead insects and grit. This is the single most useful step, so do not skip it.

### 2. Clean the rebates and channels

The rebate is the recessed part of the frame the sash closes against. Dip your cloth or toothbrush in the warm soapy water and work along the rebates and into the channels, loosening the grime the vacuum left behind. The old toothbrush is ideal for the corners where dirt collects.

### 3. Clear the drainage slots

Look along the bottom of the outer frame for small slots, sometimes hidden behind little flaps. These are the drainage holes that let water escape outside. Poke gently with the toothbrush and flush a little water through to check it runs out of the bottom of the frame, not into the room. Clearing these is what stops leaks.

### 4. Wipe the seals

Wipe the rubber seals gently with the damp cloth to lift dirt. Do not stretch or pull them out of their groove. Once clean and dry, a thin smear of petroleum jelly or silicone lubricant keeps them supple so they carry on sealing and do not crack.

### 5. Dry off and check the hardware

Wipe everything dry with the clean cloth. While the window is open, put a drop of light oil on the hinges and moving parts of the lock so it opens and closes smoothly.

## How often to do it

Two or three times a year is plenty for most homes. Do it in spring after the winter grime, again in late summer, and give the drainage channels a check in autumn before the heavy rain arrives. Windows that face busy roads or lots of trees may need it more often.

## What to avoid

- **Bleach and strong solvents**, which can discolour uPVC and perish the seals
- **Abrasive pads and cream cleaners**, which scratch the surface
- **Jet washers on the seals**, which can force water past them and damage them
- **Pulling the seals out** to clean behind them, which stops them sitting right afterwards

If a seal is already hard, cracked or coming away, cleaning will not fix it and it is better replaced.

## When cleaning is not enough

Sometimes the leak or draught is not down to dirt. If water still gets in after you have cleared the drainage, or the window will not seal even with clean, supple gaskets, the seal or the hardware may have failed. A dropped sash, a worn hinge or a perished gasket needs a proper repair rather than another clean. Our [window and door repairs in York](https://smwindowsanddoors.co.uk/window-door-repairs-york) team can sort worn seals, sticking sashes and misting units without replacing the whole window.

If the frames themselves are tired, discoloured beyond cleaning or the units have failed for good, it may be time to look at replacements. Our [uPVC windows in York](https://smwindowsanddoors.co.uk/upvc-windows-york) come in a wide range of colours and styles if you reach that point.

## Rough 2026 costs

Cleaning the inside of your frames costs almost nothing beyond a little time. If you would rather a professional gave everything a service, or a seal or hinge needs replacing, small repairs typically land somewhere around 60 to 200 pounds depending on the job, as a broad 2026 guide. Prices vary, so [request a free quote](https://smwindowsanddoors.co.uk/request-a-quote) for your situation.

## FAQs

### How do I clean uPVC window frames inside without damaging them?

Use warm soapy water, a soft cloth and an old toothbrush for the grooves, and a vacuum for loose debris. Avoid bleach, solvents and abrasive pads, which can discolour the uPVC or damage the seals.

### Why is my uPVC window leaking from the inside?

The most common cause is blocked drainage channels, so water cannot escape outside and backs up indoors. Clear the small drainage slots along the bottom of the frame first. If it still leaks, a seal or the hardware may have failed.

### How often should I clean the inside of my window frames?

Two or three times a year suits most homes. A spring clean, a late-summer wipe and an autumn check of the drainage before heavy rain will keep things working.

### Can I use bleach on uPVC window frames?

It is best avoided. Bleach and strong solvents can dull or discolour uPVC and perish the rubber seals. Warm soapy water is safer and works well for regular cleaning.

### Should I lubricate uPVC window seals?

Yes, a thin smear of petroleum jelly or silicone lubricant on clean, dry seals keeps them supple so they carry on sealing and are less likely to crack. Do the hinges and locks with a little light oil too.

Thinking your frames are past cleaning and want to see the options? [Download our latest brochure](https://smwindowsanddoors.co.uk/brochure-downloads), or [request a free quote](https://smwindowsanddoors.co.uk/request-a-quote) and we will pop out for a look.

[View full post](https://smwindowsanddoors.co.uk/blog/sm-windows-doors-blog/how-to-clean-the-inside-of-upvc-window-frames)

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