Pond Construction

by Tom Burton

The next step is to lay out the pond perimeter using powdered lime or a rope or hose to see what this thing is really going to look like in the spot you’ve chosen. Again, it’s probably good to leave this for a couple of days to see if that’s what you really had envisioned. Then, start digging.

If you live in an area where ice might be a problem, slope the sides about 20 degrees so the ice can slide up as it expands instead of straight out (and through your liner). Dig out the trench for the 4″ bottom drain pipe and run it all the way to where the rest of the filter system will go. If a straight shot is not possible, use 45-degree elbows to raise or turn the pipe rather than 90’s. The fewer bends the better. Put the bottom drain and all the pipework in place to check all the measurements before gluing. It’s a good idea to cover the whole top of the drain to keep dirt out. If the drain is sitting on firm virgin clay/soil, there’s no need to set it in concrete. The weight of the pond water will hold it steady.

Returns from the pump and filtration system to the pond are usually via a waterfall and a couple of through-the- liner bulkhead fittings that allow for the creation of a current by using directional “eyeball” (spa) fittings or 90 degree Fernco elbows with the clamps removed (so the fish don’t hurt themselves) and glued to the pipe out of the bulkhead. Don’t be afraid of the through-the-liner returns. Just be sure to tamp the backfill around each pipe so they’re in a solid setting. It usually takes two people to install them and only go arm’s length down the side – one person holds the outside of the fitting outside the pond (male threaded) while the other tightens the nut that sandwiches the liner against the flange (female threaded) for a water-tight installation. A bit of aquarium-safe adhesive wouldn’t hurt either.

Tip: Inch-and-a-half PVC, schedule 40, is good for most water transfer functions. However, if the run is longer than about 15 feet, 2″ works better by reducing flow resistance. If flexible PVC is used, be sure to use the PVC cement made for it. Also, always use PVC cleaner before gluing (a clear one is available if you don’t want to see all the typical blue around joints).

Tip: Fernco couplings make pipe joints simple. This is a rubber coupling with stainless steel clamps and comes in many configurations and is available at home centers and plumbing supply houses. After installation, check for tightness periodically if used near pumps. They have been known to loosen, detach and allow depletion of an entire pond.

Tip: Skimmers are a really “nice-to-have.” Either the inexpensive (about $40) aftermarket one or a swimming pool type that installs in the liner just like it does in a liner swimming pool. They keep the surface looking great and both require a pump to operate (external is best – 2,000 to 2,400 GPH).

You’ve already decided whether you’re going to have a partially raised pond and what that structure will be made of and look like, or you know what type of stone you’re going to use around the place. The rule here is to hide the liner and the plumbing. The water level should always be a little above the exposed liner inside the pond. This means that the liner must not only go under rocks placed around the edge of the pond, it must come up behind them as well. To accomplish this, a shelf an inch or two below the intended water line is in order (remember, you know where the water line is going to be because of the levels shot with the transit). Hiding that back edge or tip of liner can be accomplished by using overlapping rocks, plants, decking, you name it (see diagram). Here’s where your imagination comes to play. Just don’t let it show either inside the pond or out. Decide how the excavation at the top perimeter of the pond should be done to arrive at the look you intended. It’s a good idea to steer clear of a necklace or swimming pool look except maybe for a partially raised pond.

Tip: The edge of the pond should be slightly higher than grade so that rainwater doesn’t flow into the pond.

Now’s the time to check the dimensions of the pond again and calculate the size liner you’re going to need. Length plus 4′ plus (depth x 2), and width plus 4′ plus (depth x 2). That 4′ in each direction is to give you 2′ overhang all around. Thus a pond 25’ x 13’ and 3′ deep needs a piece of liner a minimum of 35’ x 23’ plus any for bog garden, streams or waterfalls. If the stones you’re using are more than 18″ wide, you will need to add liner accordingly. The rule of thumb is, if water is going to be there, there must be a covering of liner AND a lip at the back to contain it. Don’t forget to include a planned stream or waterfall. They need to be lined as well and the water contained on the sides (with the liner hidden of course). One contiguous piece for everything, to include the water garden if that’s in the plan, makes it a lot easier but there is an EPDM bonding material that does well when applied properly. Or, there is an EPDM tape that will work if applied with care and correctly. There are some good diagrams and examples of perimeter treatment in the Tetra Encyclopedia of Koi and though this book is an excellent reference, it’s rather dated, particularly in filtration, so check with other folks before accepting the material as gospel. The fundamentals are all there but technology and new developments have passed it by.

Now the hole is perfect and its time to lay padding for the EPDM. Old carpet works well, as does sand or carpet padding, almost anything that will give a bit of cushion and help the liner resist puncture from underneath. Once that’s in place you’re ready to lay the liner. And since its pretty heavy, fellow club members or friends are needed for this operation. One method is to lay the whole liner out and roll it up from the sides to the center lengthwise then tie it in a few places to facilitate carrying by you and your friends. Then march single file through the hole, placing the liner properly lengthwise, and then roll it out from the center and up the sides. Another way is to get six people to hold it out over the hole then gradually let it drop into place. Once it’s in the proper position, smooth out the bottom over the hole for the bottom drain, mark the hole with a Magic Marker, then cut the hole in the liner as neatly as possible with a utility knife. Then apply a fish friendly (aquarium safe) adhesive/caulk between the liner and the bottom drain, then on the collar that will sandwich the liner and the bottom drain together. With the collar in place install the screws or whatever fasteners came with the drain trying to apply equal tightening all around. Wait for that to set-up according to the directions for the adhesive, then proceed to lay the liner so as to avoid as many folds and wrinkles as possible (this the major down side to using a liner – some folds and wrinkles can’t be avoided and will harbor crud). This was my saddest day as I couldn’t imagine getting that huge sheet of rubber to flatten out and look like anything – but of course it mainly did and with gorgeous fish swimming around I don’t notice it anyway. As the pond slowly fills it’s possible to work even more wrinkles out as the weight of the water starts to work in your favor. It’s not a good idea though, to stretch the wrinkles out by letting water act as air would in a balloon – this ends up thinning the liner. Some folks have filled their pond, left it sit for a few days, then pumped it out and started the wrinkle removing process again as they refilled. They say it helped. Also, the use of 6″ EPDM tape can help flatten and seal major folds. The anti-vortex domed top for the drain should be set about 1 ½” off the bottom.

Tip: When filling the pond, water should be metered so you will know FOR SURE how much is in there AND in the entire filter system together. You’ll need this info if/when you must treat for parasites or other baddies as dosages are based on water volume (and no one I ever heard of has gotten away without some).

Tip: DO NOT CUT excess liner until you are SURE it isn’t needed. This is a lesson learned the hard way by too many of us.

Now to the filtration system: At this stage you should have the system all hooked up and in place or have all the necessary parts on hand. You’ve kept the water in the pond from running out the drainpipes by closing the knife valve for each. Look at the attached filter diagram as only one of many ways and means to arrive at the same end; good water quality. The filter system is the key to that and if we don’t have good water quality, we can’t keep koi (very long) – period. The system incorporates bottom drain to settling chamber to mechanical filtration to biological processing to pump to pond. It doesn’t matter what the containers look like, or what their shape is as long as they hold water and don’t lose their shape when filled. The settling chamber won’t work if we feed it too fast. The mechanical filter won’t work if all the water isn’t forced to travel through the filtration media. Likewise, the biological processing station won’t work if the water can go around the media you’ve selected as the home of the good guy bacteria. Water will seek the least line of resistance and all of your efforts will be for naught if it doesn’t go THROUGH the media. Also, match the media to the type container. Brushes do well in round, or straight-sided square or rectangular containers. Ribbon type media goes in either as well. Ribbon material will try to sneak out purge drainpipes if you don’t contain it (say in nylon drawstring laundry bags or by having a grate at the bottom of the container). However, these are just a few of the potentials for media so ask and look around. They are ones I’ve used successfully though.

Now we can start up the pump and test our recirculating, gravity fed system. The pump should obviously be outside the pond and move 2,000 to 2,400 GPH. It normally doesn’t have to create much head or pressure as water falls should neither look nor sound like Niagara Falls. The effect should be soothing, not kinetic or frantic but that’s a personal thing I guess. Most of the water being pumped will go to the through-the-liner returns to create the current we mentioned earlier. The fish love it and the crud is moved to the bottom drain where it belongs. There are several choices of pumps and any one that uses around 3 amps and is quiet will do just fine. Most have 1 ½ ” input and output connections. If you’re going to use 2″ pipe from (and/or to) the pump, just use a 1 ½ ” to 2″ coupling. Installing a ball valve (Teflon ones are best) on the output side of the pump for complete control, and a flow meter that displays 20 to 80 GPM, are highly recommended.

Tip: Amps x voltage = watts x 24 hours divided by 1000 = kilowatt hours (KWH). Example: 3 amps x 120 volts = 360 watts x 24 hours = 8640 watts divided by 1000 = 8.64 kWh x rate charged by the electric company per kWh (mine is 15 cents) = $1.29 per day to operate the pump (or $38.88 per month).

Tip: Union couplings on the input and output side of pumps make for quick disconnects.

You’re up and running now and have used some type of dechlorinator to neutralize the chlorine in the water and are ready to add a few fish that will provide the food (ammonia) for the good guy bacteria to get started. Remember that our biological processing station is only RE-active and never PRO-active so it always has to catch up to any increased bio load (so we never want to add a lot of fish all at once).

Tip: Call your water company and ask if they use chloramine to get rid of bacteria. If they do, you need a neutralizer that attacks that specifically. Just read the label on the product.

(Carolyn says: Aqua Xtreme neutralizes both chlorine and chloramines and removes ammonia and heavy metals, etc.)

Tip: An ultra-violet sterilizer is the best way to get rid of suspended algae (which makes our water green). The wattage needed depends upon a lot of things, such as nitrate in the water and hours of sunlight on the pond (algae is a plant after all and needs food and sunlight to thrive). A 40-watt UV with water flowing through it at 900 GPH, works very well for most ponds (4000 to 6000 gallons). If you need more power and water is run through two 40-watters one after the other in sequence, you can increase the flow to 1800 GPH (or 3 to 2700 GPH, etc.) Those are figures I know to work but the hobby has more art to it than science so a little deviation either way probably wouldn’t matter. A branch off of one of the returns or even placed in a return line, can supply the water but you’ll need to know what the flow rate is. Installing a flow meter in the line will take care of that and the ball valve on the line after the pump will be your control. The alternative is a separate small submersible pump (of the type without oil in it) picking up water from the processing station or the mechanical filter and pumping to the waterfall or even from one container or section to the other, will work.

Koi Club of San Diego is a 501(c)(3) organization, and all monetary donations are tax deductible to the fullest extent allowed by tax laws. Please check with your financial advisor if you have more questions. Tax Identification Number: 33-0355312

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