The hole for my pond was dug with an added three feet at the back end. Before laying the liner, I filled the back end with gravel at three feet deep by three feet wide and supported by cinder blocks. I then made the back surface a few inches shorter. Any overflow drains into the gravel.

A few years ago a stalled storm dumped over eight inches of rain in about twelve hours. The area had significant flooding, but my pond was fine. I think my floating plants and some fish would have been in the neighbors yard without the gravel.

Allow me to add my two-cents.... whether or not you need an overflow drain depends very much on three factors: 1) pond size (potential runoff volume), 2) how much it rains in your area, and 3) the pond location/placement. Larger ponds, those over 1000 gallons, do well to have an overflow drain, especially in rainy areas (I lived in Oregon/Washington for more than 20 years). However, depending on the three factors mentioned previously, and you don't mind a wet yard, the overflow drain is optional.

I'm in Southern Cal and my current 5000 gal pond has both an overflow drain and an automatic fill. Personally, I wouldn't be without either. My overflow is constructed using 2" PVC pipe and is integrated into my Savio skimmer. The skimmer required a little customizing, but it works very well. If you decide to use an overflow drain, there are many options or ways to install one suitable to your situation.

The land dips down toward my neighbor's patio near one end of my pond. I booted a 4" pipe (using abs 90 degree elbow that is easily disguised) about 1" below the top of my pond. Barrier to fish on it. It is discharged to the storm sewer system. Never had any overflow, even in Hurricane Ike aftermath. Lots of good ideas and approaches here--what suits your particular pond situation and property is what you need to decide.

I did a 2" abs pipe at a 90 degree angle and have it booted through the liner. It runs through a discharge pipe to the back of the property away from the pond. It has worked great.

Just an observation, but public sewers have a tendency to back up during extremely heavy rainfall.

Don't worry so much about letting water out - If your yard is flat make sure the edge of your pond is at least 2-3 inches ABOVE the ground. You need to keep water from running IN. You can use the dirt from the hole to bank the edge.

It's OK for water to run out of your pond and it will - no matter how carefully you make the edge level - there will be a low spot - mine is at the "beach" so the water runs through the gravel on the way out. NO fishes get washed away that way.

What you don't want is water running in - carrying dirt and other bad things INTO your pond.
sam

This topic pops up regularly. When I was planning my pond a few years ago, the advice I received was that a drain was not necessary. I had no clue how fast the pond would fill and overflow, even with siltation berms. But I did what I felt I needed for my situation.

I couldn't imagine water on my lawn because we have quite impermeable soil and a very high water table. It seemed irresponsible to ignore the potential for flooding my neighbor. I just couldn't envision a pond without an overflow. Luckily, we have a 4" storm drain pipe that runs near the end of the pond. Sewer back-up is not a factor.

In my experience in a tough building area, you have to fit your dream of a pond into the reality of the environment or modify the environment in some way. Soil drainage of overflow area, slope, likelihood of flooding your basement, run-off and erosion, some of the particulars of your property to be considered. Controlled overflow as opposed to uncontrolled overflow just works better for me and makes draining a dream.
Mike

I think everyone is overlooking one thing. The pond is not going to produce any more water on the lawn than would have been produced if the pond wasn't there. No drain is necessary. It is necessary to have the edges of the pond a few inches above the surrounding area so there isn't a reverse flow.

I do believe a drain is important for some larger ponds. I think normana61, the original poster, would be happy with a drain. What he describes is just what I have, to the street and into a storm basin. All the pipe and fittings were under $20. The labor is something else.

When you have an impervious basin, even with a berm, water on the lawn and in the pond are not the same. On the lawn there will be infiltration, run-off, factors that usually prevent puddling. Water in the pond can only rise and if it overflows it usually will puddle, especially depending on the soil and how saturated it is from rain.

Assuming there is a 2" berm. With two inches of rain the basin is full. More rain makes it overflow and that is a matter of personal preference, if it matters to the owner or not. Evaporation and possibly seepage into the berm can lower the water. However, in many climates evaporation cannot beat rainfall.

The question that I haven't seen answered much is how people without a drain do water changes or lower the water to work on the pond--pump onto the lawn or into a ditch? I wish I could have done that but find my drain so useful I wouldn't have it any other way.

As I said, it is personal preference that works in my setting. Certainly there are locations and climates where water level control isn't necessary.

This subject has interested me a lot since I was faced with my decision a few years ago. I'm sorry to keep beating a dead horse here. I'll try to not get involved next time the subject is raised--right!
Mike

I agree it is an individual site situation. My pond is plumbed directly into the sanitary sewer from my pump. I also have a line directly outside the low point in my pond plumbed to the street. But generally, a person will have no more water problem than if the pond were not there.

My pond kit has a skimmer that has an overflow outlet. We piped that outlet to a pit filled with stones and gravel i.e. a dry well. (Worked well when I forgot to turn the hose off when I was adding water to the pond)

Thank you for the responses. I guess the idea of controlling excess water is more important than what we call what it is we do-if we feel we need do anything. Dry well is a great way to go. Whether or not an overfull pond has no more impact than natural conditions is a great discussion that has had no hard facts on any side of the issue in the many posts over the years. That's what makes it enjoyable. Looks like lots of us think it just seems prudent to be able to control that water under our own conditions.

Good ponding - Mike