MAINTAINING YOUR POND

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Ice can do more than displace a horizontal outlet. When a trickle tube is installed so that the top several feet of pipe stand in open water, the pipe is vulnerable to damage from ice movement. I've heard of ice actually lifting a plastic trickle tube right out of the outlet elbow so that the pond emptied. Trickle tubes also can be pushed around by ice so they crack and leak. It makes sense to install the trickle tube close to shore, so that only a foot or two isn't packed in earth.

Installing the pipe in solidly compacted, water-retaining soil is essential. One of the worst pond blowouts I've seen occurred in a pond that had been designed with "sand doughnuts" to serve as anti-seep collars. The drain pipe had been installed with several rings of sand around the pipe, intended to prevent seepage. Water found its way through the sand, and during spring runoff the dam tore open. By the time the pond emptied, a half-mile of town road had been destroyed. Repair fees and legal expenses exceeded the original construction costs.

In addition to making sure any pond overflow system near a public road is floodproof, it's important not to locate outlets too close to roadways. Water-saturated roadbeds are easily damaged by traffic and, because they're plowed in winter, may freeze and lead to icing in nearby pipes.

In cold climates, an outlet pipe exposed to the air for any great length at the downstream end may act like an ice tray, freezing and blocking overflow. The outlet should be cut off close to the earth it's installed in, making sure that the surrounding area is reinforced to prevent erosion.

Outlet pipes can become plugged with leaves and other pond debris. Flat mesh screens and trash racks are sometimes used to keep pipes from plugging. It's important to make sure the mesh isn't so small that debris builds up and stops the outflow. If the pond owner occasionally cleans the outlet trash rack, or screen, the chances for plugging are reduced. Outlet cleaning is another good reason to site the pipe close to shore.

Outlet pipes can be plugged by animals. Beavers may block up outlet piping in an effort to raise the pond water level. It might not take long to clear the outlet at first, but beavers are persistent critters, and the pond owner may find himself in a daily struggle to prevent flooding. There are several ways to deal with beavers: They can be trapped or shot, depending on local laws and the sympathy level of the landowner. Dynamite is sometimes used to blow out beaver dams that jeopardize a pond or pose a threat downstream. Dynamite can also be used in the lodge to kill beavers, and to prevent another family from taking up residency.

But these are drastic measures, in many states against the law, and certainly not in tune with most pond owners I know. Thus, beaver inhibitors have been designed for pond outlets. The simplest is a mesh screen to prevent the animal from inserting brush or mud into the pipe. However, it's not unusual for a beaver to pack enough debris against the outlet screen to plug it, and more complicated solutions are required. One pond builder I know recommends building a dock over the outlet pipe and then wrapping the structure in wire mesh, right down to the bottom of the pilings (similar to a large trash rack). Vertical baffles on the outlet can also hinder beavers. Preventing beavers from damming a natural spillway may require more than physical removal of brush.

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