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Unconditional Satisfaction GuaranteeNo Shipping Fees Above 302 Months to Decide. Returns Simplified.Seals Active Leaks Designed for cracks with seeping or mildly leaking water. The moisture-activated formula expands inside the crack to seal voids instead of just covering the surface. Handles Small Cracks The Simpson Strong-Tie Crack-Pac Flex-H2O polyurethane crack sealer is made for cracks from 1/32 inch to 1/4 inch wide in concrete and solid masonry, right in the range where leak repair usually matters most. Standard Caulk Gun Use You can dispense it with a standard caulking tool, so you do not need a specialized injection machine for the cartridge itself. That makes it a practical option for repair crews and serious DIY users.
The Simpson Strong-Tie Crack-Pac Flex-H2O polyurethane crack sealer, model CPFH09, is a 9 oz polyurethane crack repair cartridge built for sealing leaking cracks, voids, and fractures in concrete and solid masonry. This is a polyurethane crack sealer designed for non-structural crack repair where water is seeping or mildly leaking through the crack. If your job is stopping water intrusion instead of restoring structural strength, this is the right type of product to be looking at.
What makes this product different from a basic surface patch is that it reacts with moisture and expands inside the crack. That matters because water problems in concrete usually do not stay on the face of the wall or slab. The Flex-H2O formula is built to move into the crack path and fill voids, which helps seal the affected area more effectively than a simple topcoat repair. Simpson Strong-Tie lists a 20:1 unrestricted expansion ratio, which means a relatively small amount of material can go a long way once it activates.
This cartridge is intended for cracks ranging from 1/32 inch to 1/4 inch wide. That puts it squarely in the category of fine to moderate crack sealing for concrete and masonry repair. It is suitable for dry, damp, and wet conditions, and it can even be used on dry cracks if water is introduced to the affected area. For contractors dealing with foundation walls, retaining walls, basements, pits, vaults, or pool structures, that flexibility is a big deal because jobsite conditions are rarely perfect.
From a handling standpoint, this is one of the more approachable leak-seal products in the category because it can be dispensed with a standard caulking tool. That lowers the barrier to entry for crews who already have basic application tools on hand. The accelerator is packaged in the nozzle, and Simpson Strong-Tie also notes that the reaction speed can be adjusted by using a reduced amount of accelerator or none at all when a slower reaction time is needed. That gives the user some control depending on temperature, moisture level, and how aggressively the crack is taking material.
Reaction time is fast. Exposure to moisture starts the reaction within about 1 minute, and expansion may be completed within 3 minutes depending on ambient temperature and available moisture. In real-world use, that means you need to be organized before you start. Get your ports, surface prep, and injection plan ready first, because once the material kicks, it moves quickly. Simpson Strong-Tie recommends conditioning the resin and hardener to 60 degrees Fahrenheit to 90 degrees Fahrenheit before mixing for proper component blending and expected performance.
As a cartridge product, the CPFH09 is the single 9 oz option in the Flex-H2O line. It is also listed as compatible with the Simpson Strong-Tie CDT10S dispensing tool, while still being usable with a standard caulking tool. If you need a full pressure injection setup with ports, fittings, and paste-over epoxy, Simpson Strong-Tie offers that separately as the CPFH09KT kit. That distinction matters because this specific SKU is the sealer cartridge only, not the full injection kit.
In terms of where it fits best, this product is for contractors, concrete repair techs, property maintenance teams, and capable homeowners dealing with water intrusion through non-structural cracks. It is not the product to reach for when the goal is structural bonding or load restoration. It is the one to grab when the problem is water getting through a crack in concrete or masonry and you need a moisture-activated expanding polyurethane crack sealer that works in real wet conditions.
This is where Flex-H2O earns its keep. It is built for concrete and masonry cracks that are damp, wet, or actively seeping, so you are not waiting around for a perfectly dry repair surface before you can get moving.
The cartridge format keeps this repair manageable for smaller jobs and spot repairs. You get a controlled application method without stepping up to bulk material handling.
This SKU is the cartridge only. Injection ports, fittings, paste-over epoxy, and other kit accessories are not included.
| Application | Crack Repair, Non-Structural |
|---|---|
| Material | Polyurethane |
| Container Size | 9 oz (270 mL) |
| Crack Width Range | 1/32 in to 1/4 in |
| Expansion Ratio | 20:1 unrestricted rise |
| Usage Temperature | 60F to 90F |
| Weight | 0.8 lbs |
| Shelf Life | 12 months unopened |
Dispensing Tool Can be dispensed with a standard caulking tool. Simpson Strong-Tie also lists compatibility with the CDT10S dispensing tool. Base Material Designed for use in concrete and solid masonry. System Option Also available as part of the CPFH09KT kit for users who need injection ports, fittings, and paste-over materials in one package.
Concrete Repair Masonry Repair Foundation Crack Sealing Pool Repair Water Intrusion Repair Property Maintenance General Contracting DIY / Hobbyist
Condition the material to the recommended 60F to 90F range before you start, then have your crack prep and injection setup ready first. Flex-H2O starts reacting within about a minute after it hits moisture, so this is not a product you want to pause with halfway through the setup.
Tool Nut’s Take
If you are chasing a leak through concrete or masonry, this cartridge gives you a fast, practical way to seal the crack without overcomplicating the job.
