Step 4 - Pond Overflow
One of the most important things a pond need is an overflow. During a heavy downpour, an overflow cuts the weight and stress against the walls of the pond. The wall at the lowest point of gravity is most at risk. A pond without an overflow makes it’s own, often with catastrophic results.
You can lose your fish and be forced to rebuild. An overflow reduces stress against the embankment walls.
Watch this: The Importance of Having an Overflow for Your Pond
Look for vulnerable pond walls
When I’m building a pond and a certain side of the wall looks more vulnerable to erosion, I add cinder blocks to reinforce it. One often runs into situations like this when building a pond on a hill. The lowest point of gravity is the weakest. Reinforce the wall with cinder blocks by laying them as one row, horizontally. Then bury the blocks. One time I doubled up the cinder blocks in a specific situation that worried me.
Keep these things in mind during pond construction. Starting all over again isn’t fun. I’ve had to do that with my first pond and it was a major bummer. In Florida, we have torrential downpours and sandy soil. Mass erosion and mudslides are possible. I reinforce the wall with cinder blocks and then lay sod over the entire area. When the sod roots, it helps anchor the wall in place. This drastically reduces erosion.
Setting the overflow
When you design your pond, plan to put the overflow where the water is most likely to flow out of during a downpour. Torrential downpours happen just about everywhere. Make sure to prepare your pond for when this event occurs. Plan to set the pond overflow at the lowest point of gravity.
If the pond sits on a hill, place the overflow on the lower side. I’ve had lots of experience with this particular situation. Make a trench from the spillway for the excess water to go. Avoid aiming the trench at your neighbor’s property; that’s asking for trouble. Also, excess water shouldn’t flow into the street, road or sidewalk. Take all these factors into consideration when setting a pond overflow.
How to make a pond overflow
There are different ways to make a pond overflow. One way uses pipes and filters. The problem with a piped overflow is that it gets clogged with organic matter. When that happens, you no longer have an overflow. Removing a clog from the pipe is very difficult because it’s likely clogged in more than one area. Hiring a pond contractor to come out and fix it could end up being very expensive. I’m highly against the idea of this kind of design.
Let’s avoid problems like this from occurring in the first place. Some pond contractors try to talk you into getting a piped overflow because they can charge more money. They’ll get you on both installations and try to sign you up for an ongoing maintenance plan. I never have to clean out any of my overflows or change any filters so I have no such costs.
My overflow plan
Here’s how I create a pond overflow: Take two 12 in. x 12 in. x 1.5 in. concrete pavers and lay them side by side. Then stack more on top, building them up to the level of the intended waterline.
Two pavers laying side by side allows the overflow two feet of width. I’ve never needed anything wider than that. One can then easily adjust the level of the water by simply adding or taking away two of the top pavers. They’re 1.5in thick, so it is very precise, right where you need the water to overflow from the waterline.
Make sure all your corresponding pond walls are higher than the overflow. To cover up the eyesore, one can use flagstone and river pebbles.
Now when a downpour occurs, the fish cannot swim over the overflow. You’ll also learn exactly when your pond is full when filling it manually because water trickles out through the flagstone into the spillway.
Your pond overflow is complete!
Check out the pictures
You can see on the picture to the right how I keep the front of my overflow. I prefer to keep river pebbles at the mouth of the overflow as an extra deterrent from fish being able to swim through and over the spillway. It works very well.
The only issue I have is when one of my bullfrogs hides in between the flagstones.
When she does this, she pushes some of the pebbles aside, exposing small areas of the liner. Once a week I usually have to add a few more pebbles to hide the liner. It’s still a better system than having to deal with a clog in a piped overflow.
The total cost of creating a pond overflow my way
The total cost of creating an overflow in this fashion is about $30.00 (sometimes less). You need the right amount of pavers and two bags of river pebbles (40 lbs each).
When the second pond contractor quoted me a price for a piped overflow, it was $630.00 with no guarantee the filter wouldn’t get clogged. After some other absurd quotes and ridiculous claims, I showed him the door. Another red flag which proved going with a contractor wasn’t for me.
I’d like to reiterate a point here. It’s not just about the money or going cheap. I wouldn’t have a piped overflow installed if I were a millionaire because it’s a faulty system. The cost and possible annual maintenance needed isn’t worth the aggravation. If my pond were to sustain damage to one of the walls because of a clogged pipe, it would be of tragic proportions. Most of the fish would be lost and draining the entire pond would be necessary to rebuild the wall.
Have you ever worked with muddy, wet pond liner? If you think working with a new pond liner is hard, try working with it smelly, muddy and wet. A miserable experience I can assure you. If you hire a contractor to fix it, it will cost a couple of thousand dollars. If you’re not familiar with the story behind this website, I threw away over $10,000 on a pond that a contractor installed after three months.