Best Practices | Collaborative Formal Pond Design

4 foot deep formal pond

This 4-foot-deep formal courtyard pond is sealed with polyurea.

In the past couple of years, I have been fortunate enough to help design and supply equipment for clients who are interested working with both their pool and landscape contractors to build a formal pond. Occasionally a client will retain me and then go from contractor to contractor. The contractor-client relationship can be a delicate balance of trust when it comes to building a life support system for their fish.

Recently, I had a new client, Edgar, who was moving into a new development. He had a pond at the house he was leaving, but he wanted to create a better system with lower maintenance and a formal design. Over the course of the design phase, Edgar consulted with three contractors, two of which I had worked successfully with on other projects. The third was Tim Kalkowski, owner of Nevada Pools. I had not worked with Tim, but I was excited because I had talked with him a couple of years earlier and knew he was open to building a living water feature.

Design Specs

Edgar’s pond was to be rectangular, in-ground and located in a covered side courtyard. It would be visible through glass windows and sliding doors from both the home’s entrance and kitchen with a hardscape walkway surrounding the pond. The end farthest from the house would have a low, formal spill coming from the edge of a raised patio area with a fire feature.

From a functional perspective, I couldn’t effectively use an airlift on this design because at about 3,000 gallons and incorporating a 36-inch-wide raised spill, there wasn’t enough total pond volume to use a split airlift-standard pump system. The spill would need at least 3,000 gallons per hour of flow to operate smoothly, and a split system would be more complicated than what was necessary for the total turnover rate.

The pond was to be 12 by 9 by 4 feet deep. I decided to use two 3-inch LWS aerated bottom drains each flowing to its own in-ground, 55-gallon drum radial separator and place a single LWS shelf-mounted Aqua-Niche skimmer in the top step in one corner. To pass code, the pond needed steps, so placing the skimmer in the top step was a good functional use of the space. The skimmer and bottom drains need an average of 2,000 gallons per hour each to function properly. I chose a 6,000-gph Wlim Wave I, ¼-Horsepower pump to operate the system.

The pond pump pulls from both radial separators and the skimmer through a 3-inch double wye reduced to 2 inches as an intake plenum. From there, the water is pumped to two upflow 55-gallon drum sand and gravel filters and one Air-Driven Dilution Reactor (ADDR) for aerated biofiltration. The ADDR oxygenates the pond water, making up for the lack of aeration through a waterfall or other source. The 57-watt downflow LWS ultraviolet light is mounted inside one of the sand and gravel filters. One 45 LPM Medo air pump on a timer runs both 5-inch diffusers on the aerated bottom drains with a valved manifold to balance the air flow between them. The air ring in the ADDR is powered by one 60 LPM Medo air pump, which runs continuously.

Getting to Work

Working with the crew from Nevada Pools was a great experience. Once the excavation was complete, I supplied them with diagrams for the different plumbing runs along with guidance on how to properly install them. They did an excellent job and plumbed the filters the way I wanted with very little assistance.

In progress: Two 3-inch bottom drains (left) and returns with foam rings for shotcrete. The shotcrete trough is for a stainless spill with 3-inch lines.

As a pool company, they are used to having the piping stubbed out past the rebar and capped to be cut off after the shotcrete is finished. Each penetration pipe was fitted with foam rings that would flush up with the surface of the shotcrete when finished. Once removed, they leave a cavity that mimics the size of the fitting for that position. The pipes were cut back, and after the penetration fitting was in place, the space between each fitting and cavity was foamed. The next day, after the foam was set, the excess foam was trimmed flush. The bottom drains were installed in a similar fashion, with foam rings the size of the drains. This worked well, because it mimicked the system already in place for the plumbers and inspectors.

A 3-foot-long by 8-inch-wide open trough was created behind the stainless spill to hold and distribute the volume of water coming from the sand and gravel filters. The trough was created with shotcrete during the shell shoot with the appropriate foam rings around the 3-inch pipes coming up through the floor of the 10-inch-deep trough. After the first week of cure time for the shotcrete, the Nevada Pools crew parged the entire surface with Bond-Kote as preparation for the polyurea seal coat.

Sealing the Deal

One nice side note about using polyurethane spray foam around the fittings — polyurea likes polyurethane foam. Any foam surface that is slightly exposed doesn’t create a problem for the polyurea.

The shell is surfaced with polyurea.

Paul Parszik from Artisan Aquatics arrived immediately after the Bond-Kote was cured to apply the polyurea seal coating. Once the polyurea was finished, a 6-inch strip of Laticrete 9235 was painted along the top edge of the pond to give the 6-inch water level edge tiles an appropriate surface for bonding. The face below the spill was also finished with Laticrete. Few products adhere to cured polyurea, so applying the Laticrete immediately allows the two coatings to bond together during the cure time.

The raised deck behind the spill was constructed of solid-filled block and concrete. The hardscape around the pond and across the deck was finished in Ivory Shellock Artistic Pavers that matched the surface of the backyard patio and surrounding pool. The wooden lids covering the in-ground radial separators were stained and sealed with the bottom sides coated in Laticrete 9235 to protect them from the moisture. Wooden lids over tanks with water are always an issue in the long term, but the Laticrete protects them better than anything else I’ve tried.

Filled with a water meter, the pond measured 3,206 gallons when running. The auto-fill is placed in one of the radial separators, and a valve and connector pipe between the two prefilter tanks allows for cleaning both with only one discharge pump.

Gravity Flow

pump station filters

The top edge is coated with Laticrete in 9235. The pump station with intake plenum from the prefilters and skimmer.

Many times, the weight of the water above the water’s destination will cause a surging or burping, drawing large bubbles with it. The upper surface of the water in the filters needs to be as low as possible in relation to the surface water level of its destination. A couple of inches higher is all that’s necessary for gravity flow, but when a foot or more is necessary because of location, a vertical surge or purge tank should be installed directly after the filter. This is a larger-diameter pipe of 4 or 6 inches that allows the water to slow down and purge itself of air bubbles. This pipe should extend downward below the water level of the surface destination as an equalizing chamber. A purge tank can allow remote use of gravity-flow filters on a formal pond, no matter what the location.

Representing the needs of the fish, the client and the architect as they choose a contractor affords me the opportunity to balance my relationship among all parties involved, creating a successful project. Nevada Pools has already asked me to work on another project, and I’m genuinely pleased to be able to work with them again.

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