We have mixed epoxy formulations at our plant in Mertztown since 1949, and our data sheet states clearly: not intended for structural applications. People still buy Epoxybond Pool Putty hoping to seal moving pool shells, blown return lines, and flexing vinyl. A rigid epoxy cannot stop hydraulic earth movement or hold against operating line pressure, and packing it into the wrong opening only hides the true failure until the repair bill gets steeper.
When a pool shell shifts or an underground pipe fractures, filling the surface gap simply disguises the symptom. You lose the ability to track whether the fissure is growing or pinpoint where water escapes into the ground. Here are the four pool repair jobs where our putty is the wrong material, straight off our technical data sheets.
Structural shell cracks that continue to move
A true structural crack runs completely through the gunite, shotcrete, or poured concrete shell. These fractures happen because the ground beneath the pool settled, hydro-static ground pressure lifted the floor, or the original rebar grid snapped under tension. Our putty delivers a compressive strength of 8000 psi, but its tensile strength is 1600 psi and its bond strength to sound concrete is 400 psi. It cannot knit two moving halves of a concrete basin back together.
Smearing epoxy into an active structural crack creates a rigid plug across a moving gap. As the ground shifts or the pool fills and empties, the joint flexes. Because the cured putty has a shrinkage rate of about 1 percent and solidifies into a hard mass, the movement will simply tear the plug away from the concrete wall or shear the surrounding plaster. You will lose water again, but now you cannot measure the real crack width because of the cured lump in the way.
Pressurized plumbing lines and active leaks
Epoxybond Pool Putty cures fully submerged, but it cannot cure against active water pressure pushing from behind. In an operating return line or main drain pipe, pump pressure forces water straight through the uncured epoxy mass before it can achieve its initial set. Even with the single-stick product setting in 20 to 30 minutes, hydrostatic pressure from an un-drained pipe will blow channels through the compound.
Never attempt to pack mixed putty into a pipe or fitting while the line is pressurized or gravity-draining water through the crack. The water creates weep paths through the uncured resin, leaving a porous, leaking plug.
If you have an underground pipe leak losing inches of water a day, packing putty into the skimmer throat or return fitting is useless. Cut the pipe, isolate the broken section, and replace it with proper PVC fittings.
Expansion joints designed for movement
Expansion joints between the pool coping and the concrete deck exist to absorb seasonal movement. As summer heat expands the deck and winter cold contracts it, that joint opens and closes continuously. Our cured 2-part set has a thermal expansion rate of 3.35 x 10-5 in/in/F, hardening into an unyielding solid.
Filling an expansion joint with epoxy locks the joint. When the deck expands against the rigid epoxy, the force transfers straight into the pool coping and tile line, popping tiles off the beam and cracking the bond beam concrete. Expansion joints require a permanently flexible elastomeric sealant, never a rigid epoxy putty.
Vinyl liner tears and punctures
Our putty bonds well to concrete, gunite, ceramic tile, and fiberglass gelcoat, but it does not suit a flexible vinyl pool liner. A vinyl liner is an elastic membrane hanging under constant tension, constantly stretching and contracting with water volume and temperature changes.
Putting a rigid 1/8 inch layer of epoxy on flexible vinyl produces a rigid scab over a moving surface. As the liner shifts, the bond line fails at the edges and peels loose. The correct fix for a torn liner is an elastic vinyl patch kit with solvent adhesive, which we do not make.
Use Epoxybond Pool Putty for static repairs: chipped tiles, non-moving surface plaster cracks opened to at least 1/8 inch deep, bonding fittings, or sealing dead skimmer voids. If the structure is shifting, the pipe is pressurized, or the substrate is flexible vinyl, put the epoxy away and hire a specialist.