Fort Collins Concrete Ponds

A pond that won't hold water puts you in front of a decision most people would rather avoid. The water is going somewhere, the pump runs dry by Thursday, and every fix anyone suggests sounds either too cheap to believe or too expensive to consider. We get called to sort that out more often than we get called to build new, so let's start there.

There are three real options and no fourth one. Repair the shell you have, drop a flexible liner into it and stop fighting the concrete, or take it out and build a proper reinforced basin. Which one makes sense turns on where the water is escaping and how the thing was built in the first place. A crack at a pipe penetration is a Saturday. A floor that has cracked because the ground under it moved is a different animal, and no coating in a bucket is going to hold that shut.

Three futures for a pond that won't hold water

Why concrete ponds leak in the first place

Almost never through the middle of a wall. Water gets out at the seams and the holes. The cold joint where a floor pour meets a wall pour is the single most common escape route, because that seam is a plane between two placements that happened on different days. Put a waterstop in it and it's a non-issue for good. Leave it out and no surface product fixes it from the inside.

The second offender is every pipe that passes through the shell. Skimmer, return, bottom drain, and overflow all penetrate the concrete, and each one needs a proper collar or link seal rather than a hole with mortar packed around it. The third is shrinkage cracking, which comes from concrete that dried too fast. That's a curing failure, and our wind and dry air make it easy to cause. We wet cure pond concrete for a full week.

The fourth is the ground. A basin poured on soft or uncompacted material eventually cracks because it's spanning something that gave way, and that crack is structural, not cosmetic. That's the case where we tell people to stop buying products and rebuild.

Winter is the load these are designed around

A pond in Larimer County spends a long stretch of the year with a lid of ice on it, and ice does two things concrete doesn't like. It expands as it forms, pushing outward against the walls, and it grabs the wall face as it grows so that any vertical movement drags on the shell. Vertical walls take the worst of it. Sloped or battered walls let an ice sheet ride up rather than push straight out, which is why we shape them that way whenever the design allows.

The freeze season here runs longer than it does south of us, so we build for it rather than around it. Steel both directions, thickness that isn't optimistic, waterstops at every cold joint, and real cover over the bar. For deeper basins we recommend running them through winter rather than draining, since water under an ice cap is a gentler load than an empty shell with frozen soil pushing on it from outside.

Build season is May into early October. Wall pours in high summer need shade cloth and constant wetting, because dry wind pulls water out of a fresh vertical face fast. Early fall is the nicest stretch of the year for this work: mild days, no afternoon storms building over the foothills, and a full cure before the first ice forms.

What goes into a pond we build

• Subgrade proof rolled and compacted, with soft material removed rather than covered over
• Reinforcing steel both directions in floor and walls, lapped and supported off chairs
• Waterstop set in the cold joint between the floor pour and the wall pour
• Pipe penetrations sleeved and sealed with collars, never mortared into a rough opening
• Seven days of wet cure on floor and walls, covered and kept damp
• Fill, drain, and refill before plants or fish, so any cure residue leaves with the first water