MAINTAINING YOUR POND

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Ponds are usually piped through either a horizontal or slightly tilted overflow, or through what's called a trickle tube (also known as a drop inlet). A horizontal pipe is relatively simple to install just a foot or so below shore level, with a slight downward tilt. The trickle tube is a vertical drain open at the water level and coupled by an elbow to an outlet pipe near the bottom of the pond basin. Pipes are often used in embankment ponds because they offer no-erosion overflow as well as the option of attaching a drain for repairs, clean-outs, and fish harvest.

Unless carefully installed, overflow pipe is vulnerable to an assortment of maladies. Because they often lie above frost level, horizontal water level overflows are especially subject to ice damage in winter. If the ground freezes and shifts the pipe, it's easy for overflow to sneak underneath.

During spring, the ground beneath the pipe erodes and can drain the pond, damaging the embankment in the process. Chances for this kind of blowout are greatly reduced if one or more anti-seep collars are fitted around the pipe prior to installation. The collars may be plastic, steel, or concrete. Tar is used to seal the seam. Plastic pipe is becoming popular with pond builders because of low cost and ease of handling and installation. It's light, no welding is required, and it won't rust.

Because water moves with less resistance through smooth plastic pipe than through corrugated steel, smaller diameter pipes can be used. Some pond builders are skeptical about the longevity of plastic pipe and its susceptibility to ice damage. Thus double-riveted, asphalt-coated culvert pipe is often specified by state or federal engineers, especially for larger ponds. It's important that culvert pipe be carefully coupled together using asphalt caulking, and then banded tight and welded.

A leak or modest amount of erosion around a horizontal pipe should not be difficult to fix. One resourceful pond owner told me about a shortcut remedy he devised for a water-level horizontal outlet that was leaking around the outside. He tamped down the earth above the pipe with a heavy log, and the leak stopped.

However, tearing up a trickle tube and drain deeply embedded in a dam is another matter. Such repairs can be expensive and don't always work. Tearing apart the dam may lead to subsequent leakage unrelated to the pipe, because it's difficult to restore the integrity of the dam core. It's not unusual for pond owners with leaky or eroded piping to remove the pipe completely, refill the dam with earth, and then channel the overflow down a natural spillway. I once saw a leaky trickle tube filled with concrete to solve matters; an alternate natural spillway replaced it.

George Williams, a pond builder in Cavendish, Vermont, recalls an outlet that had to be dug up and repaired twice, and it continued to leak. He finally discovered small holes drilled into the pipe. The holes had been used for wires to help secure the pipe during transportation. He repaired the holes and the outlet worked.

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