Manhole rehabilitation
SealGuard · Polyurethane groutHyperFlex Single Component Grout
A pre-catalyzed, hydrophobic polyurethane grout for slower leaks and seeping cracks, joints and honeycombed concrete. It reacts more slowly than SealGuard II, so it travels farther into the crack before it foams and sets.
Follows the crack, then fills it
Slow leaks, wide coverage. HyperFlex is pre-catalyzed, so it’s ready to pump from a standard caulk gun. It reacts with the water in the crack and expands up to 20 times its volume, filling the leak path with closed-cell foam that stays flexible.
No catalyst to measure on site, so there’s no guesswork.
Free-rise expansion up to 20 times its volume fills voids and crack networks.
HyperFlex 300 ml tube · also 5 galCures to a flexible foam that stretches about 40% before breaking (free rise, SealGuard Inc. data).
Certified to NSF/ANSI/CAN 61 for contact with drinking water, within the listing’s limits.
Pick by the job
All three are hydrophobic polyurethanes that cure without shrinking. The difference is speed and the job.
| SealGuard product | Use it for | Speed | Comes in |
|---|---|---|---|
| SealGuard II | Active leaks with fast-moving water, up to 50 gpm | 1 to 3 seconds | 600 ml dual cartridge, dual component gun |
| HyperFlex This page | Slow leaks and seeping cracks, joints and honeycombed concrete | About 30 to 60 seconds | 300 ml tube or 5 gallon pail, standard caulk gun |
| X-Seal | Sealing joints as you build or raise a manhole: sections, adjusting rings, frames | Cures in 15 minutes to 24 hours | 300 ml tube, standard caulk gun |
Filling voids behind a structure or an abandoned line? See Strong-Seal® Grout 250 and Grout 1,000.
Lining the structure once it’s dry? See the Strong-Seal® cementitious products.
Four steps to seal a crack
- DrillWith a 12 mm (about ½″) masonry bit, drill at 45° to cross the leak path about halfway through the wall. On a 6″ wall, cross it about 3″ back. Drill every 12″ to 18″ along the leak.
- FlushFlush each hole and the crack with water. HyperFlex needs water to react, so keep the area wet.
- InjectPush the nozzle firmly into the hole and pump until material shows at the leak. Move to the next hole and repeat.
- TrimOnce it has fully reacted, break or cut the nozzles off flush with the wall. Some material reacting out through the nozzle is normal.
Use a caulk gun on open cracks, joints and voids about 1/8″ and wider. For hairline cracks, inject with a pump and packers. Washing out? Pack the crack with burlap to hold HyperFlex in while it reacts. If the leak is too fast for it, switch to SealGuard II. In cold weather, warm the tubes to at least 68°F (20°C) in hot water.
See it work
HyperFlex follows the crack and shows at the surface once the leak path is full.
On the truck
What to bring, and what to do when the grout doesn’t behave.
- Hammer drill and a 12 mm (about ½″) masonry bit
- A standard 300 ml caulk gun (not sold by Fernco); a high-thrust gun is easier
- A garden sprayer with water, to keep holes and cracks wet
- Burlap, oakum or backer rod, and a putty knife or screwdriver
- A bucket of hot water in cold weather
- Goggles, chemical-resistant gloves and coveralls or old clothes
| Problem | What to do |
|---|---|
| Reacts very slowly | Warm the tubes to at least 68°F (20°C) in a bucket of hot water, and make sure the crack is wet. |
| Washes out | Push burlap into the crack with a putty knife or screwdriver. If it still washes out, switch to SealGuard II. |
| Trigger is hard to pull, or grout runs out around the nozzle | The hole missed the crack or the crack is too narrow. Re-drill at a true 45°. |
| Nozzle is loose in the hole | Wrap duct tape around the nozzle. |
| Keeps taking grout, nothing shows | You’re likely filling a void. Move to the next hole and come back later. |
| Crack is narrower than about 1/8″ | A caulk gun can’t push grout into it. That job needs packers and a pump. |
Small leaks add up fast
Groundwater that leaks into a sanitary sewer is pumped and treated along with the sewage. Set the leak rate and your cost to treat a thousand gallons to see what one leak costs in a year.
Gallons a year = gpm × 525,600. U.S. EPA figures, as reported by MSW Magazine (2018), put wastewater collection and treatment at $2 to $5 per thousand gallons. Assumes a steady leak all year; real infiltration rises and falls with groundwater and rain, so use your own flow data where you have it.
Field results
As reported by S1E, SealGuard Inc. and Trenchless Technology.
In 2014, leaking manholes 16 to 26 feet deep beside a creek were sealed with HyperFlex. Replacement had been quoted at about $300,000. Dry-weather flow fell from about 60,000 to 30,000 gallons a day.
Source: Trenchless Technology, reposted by S1EAt a pump station, two SealGuard II cartridges cut a leak of 50 gpm or more to a trickle, and one tube of HyperFlex stopped the rest.
Source: S1E customer storyIn a 110-year-old drinking water pump station, crews worked from the basement side of a 60 by 12 foot cracked wall leaking 40 to 50 gpm. They stopped the worst leaks with 24 SealGuard II cartridges, then injected 350 lb of HyperFlex. Divers on the water side confirmed no grout escaped.
Source: SealGuard Inc. case studyWhat to order
| Part number | Description |
|---|---|
| SG-HF6 | HyperFlex, 300 ml tubes, 6 pack |
| SG-HF12 | HyperFlex, 300 ml tubes, 12 pack |
| SG-HF12TIP | HyperFlex tips, 12 pack |
| SG-HF5G | HyperFlex, 5 gallon container |
Not sold by Fernco: the caulk gun, drill bits, and a grout pump for the 5 gallon container.
Watch it work
SealGuard II and HyperFlex sealing infiltration in a manhole, with no digging.
Specifications
| Type | Pre-catalyzed, single-component hydrophobic polyurethane grout |
| Packaging | 300 ml tube; 5 gallon container |
| Reaction time | About 30 to 60 seconds. Warmer material reacts faster. |
| Expansion | Up to 20:1, free rise |
| Shrinkage (ASTM D2126) | 0% at −20°F, 1 day |
| Viscosity at 68°F | 375 cps |
| Specific gravity at 60°F | 1.18 |
| Solids | 100%, no solvents |
| Color | Amber |
| Free-rise properties | Compressive 125 psi, tensile 75 psi, shear 50 psi, elongation 40% |
| Certification | NSF/ANSI/CAN 61, cold water (23°C), listed as Hyperflex STI-03-0.15S (SealGuard Inc.). Limited to 1% of the surface area of a 9,000 gallon tank (0.03 sq in per liter). Minimum cure 2 hours at 65°F. |
| Drill size | 12 mm (about ½″) masonry bit |
| Equipment | Standard single-component caulk gun; a grout pump and packers for the 5 gallon container (not sold by Fernco) |
| Storage | Store under 80°F and keep sealed until use. The material reacts with moisture. |
| Shelf life | Two years minimum, unopened |
| Transport | U.S. D.O.T. unregulated, Class 55 |
| Typical uses | Cracks, honeycombed concrete, expansion and cold joints, pipe penetrations and slow leaks in brick, in manholes, tunnels, culverts, parking decks and dams |
What goes in the submittal
Chemical grouting of sewer manholes is covered by ASTM F2414, Standard Practice for Sealing Sewer Manholes Using Chemical Grouting, and by NASSCO’s Manhole Rehabilitation Performance Specification Guideline (2025). NASSCO calls for grouting only structurally sound manholes, after frame, cover and grade ring work is done. Values on this page come from SealGuard Inc. data. Ask us for the full package: data sheet, safety data sheet, NSF listing (HyperFlex), installation instructions and the chemical resistance chart. Send us your spec and we’ll show you where SealGuard fits.
Common questions
HyperFlex or SealGuard II?
Use HyperFlex on slower leaks and seeping cracks and joints. It reacts in about 30 to 60 seconds, so it spreads farther before it sets. For fast, active leaks, use SealGuard II, which reacts in 1 to 3 seconds.
Do I need a catalyst?
No. Many single-component grouts are sold with a separate catalyst you mix in on site. HyperFlex comes pre-catalyzed, so you load the tube and inject.
Polyurethane or epoxy for a leaking crack?
Epoxy injection bonds a crack back together, but the American Concrete Institute notes that if a crack will keep moving, an epoxy repair may not be suitable, and damp cracks need a moisture-tolerant epoxy. HyperFlex needs water to cure and stays flexible, so it suits wet, leaking cracks. For a dry structural crack, epoxy may be the right call.
Can I use the rest of a tube later?
Yes. The catalyst is built in, so a partly used tube or pail can be resealed and used later. Keep it sealed; it reacts with moisture.
Hydrophobic or hydrophilic grout?
Both are used to seal manholes. Hydrophilic grouts absorb water and can shrink if the ground dries out, then swell again when it’s wet. Hydrophobic grouts like SealGuard push water out as they cure and hold their size wet or dry, which suits manholes where the water table rises and falls. Check what your spec allows.
Can I adjust the reaction time?
Not with an added catalyst. You set the speed by picking the product: SealGuard II reacts in 1 to 3 seconds for fast leaks, and HyperFlex in about 30 to 60 seconds, so it travels farther. Temperature fine-tunes it: warm cold cartridges in hot water for about 10 minutes, or set them in 70°F water to slow them down. If your spec requires a catalyst-adjustable grout, ask us about an approved-equal review.
Does grout make the manhole stronger?
No. Injection grout stops water. It doesn’t add structural strength. NASSCO’s manhole rehabilitation guideline says to grout only structurally sound manholes, and to finish frame, cover and grade ring work first. If the walls are deteriorated, stop the leaks, then restore the structure with a Strong-Seal® liner.
How do I confirm the leak is sealed?
Look first: the joint or crack should be dry, with no running or weeping water. For a fully rehabilitated manhole, NASSCO’s guideline calls for a vacuum test to ASTM C1244. Many utilities also compare flow meter readings before and after the work.
How long does a grout repair last?
There’s no lab test that predicts the service life of injection grout, and we don’t make a lifetime claim. For planning, the U.S. EPA’s 2004 report to Congress, citing ASCE, lists 15 years for chemical grouting of manholes and 50 years for structural lining or replacement. Results depend on how fully the leak path is filled and the condition of the structure.
Does it hold up to chemicals?
SealGuard Inc.’s chart for cured polyurethanes rates resistance as excellent to water, brine, diesel, gasoline, motor oil, chlorine, wet hydrogen sulfide and 10% sulfuric acid. It rates concentrated nitric and sulfuric acid as not recommended, and acetone and MEK as poor. The chart doesn’t state a test method or exposure time. It’s in the documents below.
How do I clean up?
Snap the used mixer or nozzle off with a sharp downward motion and scrape off excess once it’s cured. Cured foam and empty cartridges or tubes can go with ordinary construction waste. For anything uncured, follow the safety data sheet. Wear old clothes: cured grout doesn’t wash out.
Does it need water to react?
Yes. Make sure the area you’re grouting is wet. Flush the drilled holes and the crack with water before you inject.
Is it approved for drinking water?
HyperFlex is certified to NSF/ANSI/CAN 61 for contact with potable water, for up to 1% of the surface area of a 9,000 gallon tank, with a minimum cure of 2 hours at 65°F.
What about cold weather?
Cold slows the reaction. Warm the tubes to at least 68°F (20°C) in hot water before use. Below about 40°F, cure can take days instead of hours.
Can I line over it?
Yes. Stopping active leaks is the first step before lining a structure, because a cementitious liner needs a surface with no running water. Once the leaks are stopped, the structure can be lined with a Strong-Seal® liner.
What safety gear do I need?
SealGuard products are MDI based and can cause skin and breathing sensitization. Wear goggles, chemical-resistant gloves and coveralls, use respiratory protection where ventilation is poor, follow your confined-space procedures, and read the safety data sheet before you start. It lists other hazards too, and it’s in the documents below.
Documents
Sell sheets, installation instructions, safety data sheets and the chemical resistance chart, plus the Fernco Infrastructure catalog.
HyperFlex Sell SheetSell sheet · PDFView PDF 
HyperFlex Installation InstructionsInstructions · PDFView PDF 
HyperFlex Sell Sheet (French, Canada)Sell sheet · PDFView PDF 
HyperFlex Safety Data SheetSDS · PDFView PDF 
Chemical Resistance ChartChart · PDFView PDF 
Fernco Infrastructure CatalogCatalog · PDFView catalogInterested in carrying Fernco Infrastructure?
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