If you use expanding foam guns for sealing gaps, insulation or general DIY joinery, it’s key to keep your gun clean after every use. A blocked or dried-out gun can waste product, slow down your work and cost you more in the long run. Follow these steps to learn how to clean an expanding foam gun, why it matters, and the tools you’ll need.
Whether you’re a DIYer installing insulation, filling reveals or finishing off a renovation, this article will walk you through every step.
Why Cleaning Your Expanding Foam Gun Matters
Knowing how to clean your foam gun is essential for consistent performance and long-term reliability. PU foam begins curing the moment it makes contact with air, which means any foam left inside the gun will gradually harden. Once this happens, the internal pathways, ball valves and needle mechanisms become blocked, causing the gun to misfire, lose pressure or stop working entirely.
A foam gun that is not cleaned properly can also waste significant amounts of product. Cured foam inside the barrel forces users to apply more pressure on the trigger, which increases the chance of spluttering or uneven output. This affects accuracy and can result in gaps that are not properly filled. In addition, clogged guns often cause foam cans to depressurise prematurely, meaning the full can cannot be used.
Clogged guns are also more prone to leaking. As hardened foam prevents the needle from sealing correctly, foam can escape around the nozzle or trigger. Apart from being messy, this can make the gun unsafe to use and difficult to recover. Over time, dried foam can corrode or damage internal components, reducing the lifespan of the gun significantly. Some manufacturers note that regular cleaning can extend the life of a professional foam gun by several years, while neglected guns often fail within months.
In short, keeping your expanding foam gun clean ensures smoother output, less wasted product and a longer-lasting tool. It also makes your work neater, faster and far easier as you avoid the frustration of sudden blockages or a gun that no longer sprays evenly.
What You Need Before You Start
- Expanding foam gun cleaner as your main cleaning product.
- Disposable gloves
- A lint-free cloth or paper towel
- A waste bin or disposable bag
- Replacement nozzles or needle tips
- A fresh can of expanding foam for after cleaning.
How to Clean an Expanding Foam Gun Step by Step
Cleaning your foam gun properly ensures smooth output, prevents clogging and keeps the tool working reliably for future projects. Follow these simple steps to remove uncured foam and keep internal components free from blockages. It’s important to note that most cleaning issues come from skipping the flushing stage or allowing foam to harden inside the gun.
Step 1. Remove the Foam Can
Start by unscrewing the used can of expanding foam from the gun. Do this slowly to release any remaining pressure. Most PU foams continue to expand for a short period after use, which means residual pressure can cause small spurts of foam if the can is removed too quickly. Foam begins to cure immediately after air exposure, so start cleaning the gun right away.
Step 2. Attach the Foam Gun Cleaner
Shake the foam gun cleaner and screw it onto the gun in the same way you attach a foam can. Cleaners contain solvents that dissolve uncured PU foam, allowing it to flush out of the internal barrel and needle assembly. This step is crucial because once foam cures, no chemical cleaner can dissolve it fully.
Step 3. Flush the Gun Thoroughly
Pull the trigger repeatedly to allow the cleaner to circulate through the gun. Continue until the liquid coming from the nozzle is completely clear. Many manufacturers recommend flushing until at least half of the cleaner can has been expelled. This ensures that every internal passage, including the ball valve and trigger mechanism, has been cleared of residue. Tremco notes that incomplete flushing is the main reason guns continue to clog even after cleaning.
Step 4. Clean the Exterior Components
Use a lint-free cloth soaked in a small amount of cleaner to wipe away foam on the outside of the gun. Remove residue from the barrel, trigger, nozzle and threaded connection. Foam left on external surfaces can harden and interfere with moving parts such as the trigger return spring. External cleaning also prevents accidental transfer of cured foam onto finished surfaces.
Step 5. Purge the Gun With Fresh Foam (Optional but Recommended)
Once the cleaner has done its job, you can briefly attach a new can of expanding foam and pull the trigger until the foam flows smoothly. Professional installers use this technique to re-lubricate the gun and remove any air pockets created during cleaning. It helps ensure the gun is ready for immediate use on your next project.
Step 6. Store the Gun Correctly
After cleaning, store the gun upright in a dry environment. If you plan to use the foam again soon, you can leave a can attached because PU foam remains usable inside a sealed gun for several weeks.
How to Clean Your Foam Gun After Every Use vs Deep Cleaning
Keeping your expanding foam gun in good condition depends on how often you use it and how long you leave foam inside the gun. There are two levels of maintenance: a quick clean after each use and a deeper clean that removes more stubborn residue. Understanding the difference ensures you avoid blockages, wasted foam and premature tool failure.
Cleaning After Every Use
A quick clean after each job is the most effective way to prevent foam from curing inside the gun. Manufacturers note that uncured foam can remain workable inside a sealed system for several weeks, but once the gun is removed from the can or exposed to air, the curing process begins immediately. PU foam starts forming a skin within 5 to 10 minutes of air exposure, making immediate cleaning essential.
After removing the foam can, attach a can of foam gun cleaner and flush the gun until the expelled liquid runs clear. Wipe the exterior with a cloth soaked in cleaner to remove any residue before it hardens. This level of quick maintenance prevents build-up, reduces the risk of blockages and keeps the trigger mechanism working smoothly.
When to Perform a Deep Clean
A deep clean is needed when the gun has been used multiple times without flushing or when foam has begun to cure inside the barrel or around the needle assembly. Signs include stiff trigger movement, restricted flow, uneven spray or visible dried foam around the nozzle. In these situations, a standard quick clean is unlikely to remove all the residue.
To deep clean the gun, use a larger amount of foam gun cleaner and take extra time to flush the internal chambers thoroughly. You may also need to remove the nozzle to scrape off hardened foam manually.
Choosing the Right Level of Cleaning
If you use the gun frequently and keep a pressurised can attached between jobs, a quick clean after each session is usually enough. However, if the gun has been left unused for weeks or has been exposed to air, a deep clean is often necessary to restore performance.
Understanding these two levels of maintenance helps you preserve your foam gun, avoid unnecessary replacements and achieve cleaner, more reliable results on every project.
Troubleshooting Common Foam Gun Problems
Even with regular cleaning, expanding foam guns can develop issues over time. Most of these problems come from cured foam, worn internal seals or incorrect storage. Understanding the symptoms and knowing how to fix them helps you avoid wasted materials and unnecessary replacements. Below are the most common issues DIYers face and how to resolve them using manufacturer-recommended practices.
Problem 1. The Gun Is Blocked or Not Dispensing Foam
A blocked foam gun is usually caused by foam curing inside the barrel or around the needle valve. PU foam hardens through a chemical reaction with moisture in the air, and once cured, it cannot be dissolved by cleaners. According to industry data, PU foam begins curing within minutes and becomes fully hardened within 8 to 24 hours, depending on conditions.
How to fix it:
- Attach a foam gun cleaner and flush the gun repeatedly.
- If flushing does not clear the blockage, remove the nozzle and scrape away visible cured foam.
- For internal blockages that cannot be reached, a deep clean may be required or the gun may need replacing.
Problem 2. The Trigger Is Hard to Pull
A stiff trigger often means cured foam has built up around the needle assembly or inside the trigger mechanism. This restricts movement and reduces control over the foam output.
Solution:
- Use foam cleaner on the trigger area and allow it to soak for a few minutes.
- Wipe away loosened residue using a cloth.
- If stiffness continues, perform a deeper internal flush.
Problem 3. Foam Is Leaking Around the Nozzle or Threads
Leaks typically indicate either a worn seal or foam residue preventing the valve from closing correctly. Foam that cures around the tip creates gaps that force material out at the wrong angle.
Solution:
- Clean the exterior thoroughly and remove any cured foam.
- If leaking persists, check whether the nozzle needs replacing.
- Ensure the foam can is screwed on tightly and the adaptor threads are clean.
Problem 4. The Gun Produces an Uneven Bead
An inconsistent foam line can be caused by an air pocket created during cleaning, partially cured foam inside the barrel or a failing ball valve. Tremco highlights that air pockets often occur when a gun is not properly purged after cleaning.
Solution:
- Purge the gun with fresh foam for a few seconds.
-
Flush again with cleaner if the problem continues.
Inspect the tip for buildup that may be narrowing the opening.
Problem 5. The Foam Can Will Not Pressurise the Gun
If attaching a new can does not pressurise the gun, the internal valve may be blocked or the can’s trigger pin may not be engaging fully.
Solution:
- Ensure the can is screwed on completely.
- Clean the connection point with foam cleaner.
- Try another can to confirm whether the issue is with the gun or the product.
- If neither works, the gun may need replacing due to internal damage.
When to Replace the Gun
If blockages are deep inside the barrel, if the trigger remains stiff after cleaning or if the gun leaks consistently during use, it is usually more economical to replace the applicator. Manufacturers state that well-maintained guns can last for years, but neglected guns often fail prematurely.
Pro Tips for Long-Term Foam Gun Maintenance
Keeping your expanding foam gun in excellent condition does not require complicated work, but it does require consistency. Regular cleaning, proper storage and correct handling can dramatically increase the lifespan of your gun. Many manufacturers note that well-maintained applicators can last for years rather than months, which makes good maintenance both time-saving and cost-effective. Below are practical, expert backed tips to help you maintain performance over the long term:
- Always Leave a Can Attached if You Will Use It Again Soon
- Store the Gun Upright
- Avoid Letting Foam Cure Inside the Gun
- Use the Correct Cleaner Every Time
- Inspect the Nozzle Regularly
- Perform a Deep Clean If You Notice Performance Changes
- Replace Worn Guns
Shop Foam Cleaners and Expanding Foam Guns
If you want your expanding foam gun to perform reliably on every project, the right cleaning products and accessories make all the difference. At Construction Megastore, we stock a full range of foam gun cleaners, PU foams and professional-grade applicator guns so you can maintain your tools properly and achieve clean, consistent results every time.
Foam Gun Cleaners
Keep your gun free from blockages and dried foam with our specialist cleaners. These are formulated to dissolve uncured PU foam quickly and safely, helping you extend the life of your gun and maintain smooth performance.
Shop Foam Gun Cleaner
Expanding Foam Guns
Whether you need a lightweight DIY model or a high quality professional applicator, our range covers all budgets and project types. These guns offer reliable control, precise dispensing and improved efficiency on every job.
Shop Expanding Foam Guns
PU Expanding Foam
Pair your applicator with the right foam for insulation, gap filling or airtightness. We supply a wide selection of PU foams from trusted brands suitable for construction, DIY and renovation work.
Accessories and Replacement Parts
From spare nozzles to adaptors, cleaning cloths and protective gloves, you will find everything you need to maintain your gun and keep your work area clean and safe
Why Buy From Construction Megastore
Customers choose us for competitive pricing, fast delivery and trusted products used by both DIYers and trade professionals. Our expert team can help you select the right foam, cleaner or applicator so you can get the job done properly the first time.
