When can I return my item?

Returns are accepted within 30 days of the original purchase date.

How do I get the item back to you for a refund?

It is your responsibility to get the item/s back to us for any consideration of a return or refund. All items returned are required to be accompanied with the original sales order number or a copy of your paperwork to facilitate the process.

Do you charge a restocking fee?

No restocking fees are charged on items held on our shelf

How will I get my refund?

Refunds are offered only on the items purchase – if items or packaging is damaged or components are missing, part refunds may be offered (this is at the discretion of management). No refunds are offered on the original postage charged, only on stock returned undamaged. Refunds are processed back via the original purchase method.

Can I return a special order in item?

Special order items DO NOT attract an automatic return or refund – as they have been special ordered in. We are governed by the supplier of the special-order stock to see if they will offer a return or refund. Many will not offer refunds; many will charge restocking fees. For consideration of a return of a special-order item, you would be best to approach the Mr Windows team before shipping the item back to us.

The leading reseller and manufacturer of obsolete sliding window parts, shower parts and sliding door parts in Australia with over 4000 different products to choose from! We offer quality products at competitive prices; with friendlier customer service than many other distributors out there. Trade Customers & Business Customers can expect great volume pricing so you can get big orders going, and get that competitive edge. For all things Windows, Sliding Door Parts & Showers, we're here with the solution.

Do You Repair Doors, Windows or Showers?

Sadly we do not perform maintenance or repairs ourselves anymore. We have decided to focus on parts and hardware while giving any enquiries for repairs or maintenance to trusted, local trades people.

Are Sliding Glass Door Rollers Universal?

The answer is generally no, whilst there are some rollers that can be used in various brands. Most door rollers are designed for the specific manufacture and series of door, so they are not universal or generally interchangeable. If you are not sure what brand of door you have, check out our resources section, in their you will find the sliding door decal guide this shows the most common decals or motifs that are used by the major brands in the center of their glass door panels. Once you identify the brand you can then search on our site. If you are still unsure, then send us a PDF or JPeg image of your door roller carriage, no need to remove it leave it in the door panel and send this photo to us and the team will do the rest to assist you in your search.

What Is The Hardware On A Door Called?

Furniture generally refers to the handle and the components therein in its entirety. Lever Handles are exactly as they sound. Typically not found on sliding doors, they use a lever action to open, close and lock. Mortice Lock is found inside of the extrusion. The lock body is hidden away inside the door itself.

What Is Dummy Door Hardware?

Dummy Hardware refers to the Sliding Door Handle or Furniture that has no locking mechanism. Often used on the internal of a door.

What Are Door Knob Screws Called?

These screws are often referred to as Grub Screws or Set Screws.

How experienced is your team to help me?

Over 50 Years Of Experience. We are capable of identifying and troubleshooting Window Parts, Sliding Door Parts & Shower Parts dating back as far as the 1960's. With a culture and ethos fostered and focused around restoration and repair before entire replacement, you can be certain we will find a solution for you that is cheaper than a new window, sliding door or shower.

BSI spring balance number on back of unit

April 14, 2026

How to Replace a BSI Spring Balance (Single & Double Hung Windows) - Easy DIY Guide

Replacing BSI spring balances might sound technical, but it’s actually a straightforward job you can complete with minimal tools and a little care.

If your single hung or double hung window is becoming hard to lift, won’t stay open, or feels heavy, the balance springs are likely worn out. Like all moving hardware, they have a shelf life based on usage.

In today’s guide, we’ll walk you through the process step by step, just like in our video tutorial (which you can watch below 👇).

What Do BSI Spring Balances Do?

BSI spring balances are designed to:

Support the weight of the window sash
Make lifting smooth and easy
Hold the sash in position when open

When they wear out, your window may:

Slam shut unexpectedly
Be difficult to lift
Feel uneven or unstable

The good news? They’re replaceable and all work is done safely from inside your home.

Tools You’ll Need

Flat-headed screwdriver

That’s it. No complicated tools required.

Before You Start

Ensure the window is fully closed
Clear a safe working area
Remember the sash may be heavy, work carefully

Step-by-Step: How to Replace a BSI Spring Balance

Step 1: Remove the Sash Stops

Locate the sash stops at the top of the window frame.

Using your flat screwdriver:

Carefully remove both sash stops.
Put them aside safely for refitting later.

Step 2: Release the Retaining Clips

Next, locate the small silver metal retaining clips in the window frame.

Insert your screwdriver at the bottom of the clip.
Gently lever it outward.

These clips hold the spring balances in position.

Step 3: Disengage the Balance Springs

Slide the window sash upwards above the retaining springs.
This disengages the balance springs from the sash.

Now move the sash to one side of the frame so you can remove it completely.

⚠️ Go carefully, the sash may be heavy.

Step 4: Remove the Old BSI Spring Balance

To remove the balance:

Slide it downwards.
It will unclip from the retaining clip.
Lift it out of the window frame.

On the back of the balance, you’ll find the BSI balance number.

👉 This number is critical.
Use it to search for your replacement on our website.

If it’s not in stock, we can arrange a special order for you.

Step 5: Install the New BSI Spring Balance

Now for the easy part, installing the new one.

Insert the small metal hook into the slot in the window frame.
Slide the spring balance downwards.
Insert the top into the spring retaining clip.
Repeat on the other side.

Spring balances installed ✔️

Step 6: Reinstall the Window Sash

Lift the sash back into the frame.
Position it above the balance hardware on one side.
Move it across and locate it into the other side.
Centre the sash and gently lower it down.

You’ll feel the balances engage and take the weight.

Step 7: Secure Everything

Push the retaining clips back flush with the frame.
Refit the sash stops.
Test the window operation.

And that’s it, job done ✅

Watch the Full Video Tutorial

Finding the Correct BSI Spring Balance

The balance number located on the back of your spring is the key to ordering the correct replacement.

If you're unsure, don’t stress.

At Mr Windows, we make it simple:

📧 Snap a photo (JPEG or PDF format)
📨 Email it to our team
📩 Our system will automatically send you a ticket number
🔎 We’ll source the correct hardware for you

We’re all about solutions.

If you’re looking for other window or door hardware, browse our full range.

Frequently Asked Questions (FAQ)

What is a BSI spring balance?

A BSI spring balance is a tensioned spring mechanism inside single or double hung windows that supports the sash weight and allows smooth opening and closing.

How do I know if my window balances need replacing?

Common signs include:

Window won’t stay open
Sash drops suddenly
Window feels heavy to lift
Uneven movement on one side

Can I replace BSI spring balances myself?

Yes. It’s a straightforward DIY job requiring only a flat-head screwdriver. All work is done from inside the home.

Where do I find the balance number?

The BSI number is located on the back of the spring balance itself. Remove it from the frame to locate the marking.

What if my balance number isn’t in stock?

Contact the Mr Windows team with your number or a photo. We can assist with special orders if needed.