Loch Lomond Pond Detail Page

This page describes the details behind the history, design and construction of our backyard pond, Loch Lomond (jr.).

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Last Updated: August 30, 1997.

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This material is Copyright 1997 Craig Buchanan. All rights reserved. This page may be freely linked to.
Please send comments or questions to
mailto: buchananc@acm.org.


Pond History

Although I had intended to build a pond for a long time the quest to design and build a pond didn't start until the summer of 1994. I used several sources in my quest to develop a good pond design including:

Unfortunately I didn't have a “suitable” spot in the backyard in which to build a pond. The two essential properties I was missing were:

In the end I chose the best spot in terms of dedicating the space. The ground had quite an incline at that spot which would require building up that section of the yard. I situated the pond across the incline to minimize the effect of the incline.

In trying to work out all of the details of the project before beginning it looked as though I might never begin. In the end I decided I wouldn't have it all figured out until I was done so I began the pond's construction (digging the hole) when I had all the basics figured out. I knew where I wanted everything, I just wasn't sure how I would build it all. Of course it's much more exciting changing the design of things as you're building them (not to mention making them much more challenging). (A systems engineer at work asked me if I ran my system projects the same way, start now and figure it out later. I told him no, but when you lack experience the only way to find all the trouble spots is to run into them.) The design evolved by working backwards. The discharge hole in the pump house depends upon the plumbing in the reservoir which depends upon the pump and its plumbing which …

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Pond Design

The design called for the following:

Given the pond's location under the trees and the known problems leaves cause I thought the pond should have a good current from one end to the other leading into a pond skimmer which would catch the leaves before they could sink to the bottom.

The skimmer would remove large debris from the water but I also wanted some filter medium ahead of the pump to keep dirt out.

The biofilter's job is to provide a place for aerobic bacteria to live. The bacteria break down the fish wastes in the water. Plants would be used to remove the nutrients produced by the fish waste. I designed the biofilter to aerate the water before it enters the biofilter medium.

The pump house was designed to house the skimmer, the filters and the pump. The filters and pump are in a reservoir which is fed by the skimmer.

I designed and built all of the plumbing in such a manner that most pieces can be easily removed for cleaning or replacement. For example the reservoir can be removed from the pump house and the pump can be removed from the reservoir.

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Pond Construction

The Pond - Take 1 - In before Winter.

The original plans called for a pond, a stream and a waterfall. I decided that it was too much work to do all at once and would build the pond the first year and the stream and waterfall the second.

The pond wasn't constructed in an entirely logical order. The pond was constructed as follows:

The biggest problem is what to do with the dirt. As the landscaping around the house had settled over the years I used the dirt around the sides of the house and made a large mound in the landscaping where the stream and waterfall would go. The hole was dug with a shallow surround for the flagstone surround and deeper shelves for plants. The rocks, clay and tree roots all presented their own challenges.

According to everyone I talked to, the biggest mistake people make with their first pond is they make it too small and end up building a second larger pond. I toured one pond owner's yard where he had built a bigger pond every year for four years. I made the pond as large as I could fit into my limited space and within my budget for the pond liner.

The skimmer was purchased at a local pool supply house. I purchased the largest capacity pump I could find, it's a Little Giant 1200 gal/hr model. I bought it at a discount hardware store. The reservoir is a tall office style wastebasket purchased from another discount hardware outlet. The wastebasket was selected using the basic dimensions of the skimmer and pump. It was quite a task finding a suitably sized container as most were too short. I used a Tucker 52 quart wastebasket (model #1059).

I had decided to use 1” pvc pipe for the pond. Ideally I wanted 1” pvc compatible bulkhead fittings for the reservoir and biofilter. The largest fittings my local commercial plumbing supply house had were 3/4", I bought 4 of them.

The pump has a 1” threaded fitting on its base which points straight up. This led to a geometry problem. The exit must be horizontal so a 90 degree elbow is required. All plumbing must fit under the filter mats. The filter mats should be as low as possible to provide a height difference with the skimmer as the reservoir is gravity filled. The pump is quite tall. The plumbing must fit under the height of the pump. The threaded pump fitting meant the pipes need to be free to twist but the 90 degree elbow below the top of the pipe meant the pipes couldn't twist. In addition I needed room for a decoupling joint

The solution was to use a clamped rubber connector to connect the pieces after they were screwed into place. In the end two 90 degree elbows, a rubber connector, a decoupling joint and a bulkhead fitting were used.

The return water bulkhead fitting which came with the pool skimmer was used as an inlet to the reservoir. The fittings directional nozzle was removed to allow easy water passage. The reservoir is gravity filled but pump emptied.

The pump house is a five sided wooden box made out of 2x10 and 2x8 pressure treated lumber. The two sizes were used to stagger the seams so the boards could be screwed together at the corners. The pump house was sized to fit the skimmer and the reservoir. I cut the opening for the pool skimmer and drilled holes for the mounting screws before I assembled it. After it was assembled I cut a hole for the discharge (return) pipe and a hole for the plastic conduit which would carry the electrical service. The entire box was then painted in Elasto-Seal to make it water tight. This wasn't strictly necessary but I needed to waterproof the opening to the skimmer and thought I might as well do the whole box for good measure. (The wood between the skimmer front plate and the skimmer body, a good inch and a half, is exposed to the water.)

I actually filled in some of the pond in front of the pump house to give me room to move the return pipe into the ground along the side of the pond. The dirt was used to build a deep plant shelf in front of the pump house.

A large, sturdy, hard plastic storage container (27"x18"x18") with a hinged lid was purchased from a national, members only discount club. (It was on sale.) The water enters a pvc screw fitting connected to a spray bar. The spray bar is a piece of 1” pvc with two rows of holes drilled at 90 degrees to each other. The spray bar ensures good aeration. The water collects in a lattice of pvc pipe at the bottom of the container. The lattice pvc is covered in holes and connects to an upright and exits through a bulkhead fitting. The vertical pipe off the lattice has no exterior holes to ensure that the water's pressure due to its depth is not lost. A smaller pipe connects to the bottom of the lattice and exits the box through a homemade bulkhead fitting. This pipe is used to backflush and clean the collection lattice. (Without removing the filter medium.) Lava rock was chosen as the filter medium as it's cheap and readily available. (It is heavy however.)

Although a longer total distance, it seemed more useful in the long run to run electricity to the gazebo first and then to the pump house. A small exterior circuit panel was installed next to the external air conditioning panel. The exterior panel contains a single ground fault circuit breaker connected to the main circuit panel in the basement. A trench was dug between the house, the gazebo and the pump house pit. Plastic electrical conduit similar to pvc was installed in the trenches. An electrical fish tape was used to pull the wiring from the circuit panel to the gazebo. The last length of conduit intended to enter the pump house was left loose for later connection. After testing the service to the gazebo the electrical trench to the gazebo was filled in.

The pump house was lowered into its hole using the flat plastic straps from the pond liner box.

Not wanting to dig a trench for the return water pipe (I had already battled enough tree roots) I decided to dig into one wall of the pond instead. The original idea was to have a single, straight pipe with a constant incline which could be drained at the pump house in preparation for winter. Unfortunately the return pipe reached the pump house at an angle. This problem was overcome by installing two 45 degree elbows and a short length of offset pipe to bring the pipes into alignment. Care was taken to ensure the pipes and fittings would still drain completely. The extra plumbing was buried by making a deep plant shelf in front of the skimmer.

The return pipe connects to a valve inside the pump house. The reservoir was temporarily installed and the return pipe was cemented to the valve.

The loose conduit was connected to the pump house and cut to fit. The pump house outlet was then connected to it. An electrical fish was used to pull wire from the pump house to the gazebo. After testing the outlet in the pump house the electrical trench to the pump house was filled in.

The hole was lined with a layer of sand and then a layer of old carpet underpadding I had saved when we had some carpeting replaced. A 40 ml liner from Tetra Pond was used. The Tetra liners come plain and with integral underpadding, I opted for the plain variety. The liner is heavy and quite difficult for a single person to maneuver. A couple of neighbors helped me position the liner.

The first job was to connect the liner to the skimmer. The pond was partially filled to ensure the liner was in place so the skimmer could be installed. The skimmer is held in place by long screws which go through the skimmer front plate, then the pump house, and finally into the skimmer body. After the skimmer was installed, a hole was cut in the liner for the skimmer opening.

The second job was to install and connect the reservoir to the skimmer. The skimmer and reservoir had slip fittings and the plan called for a length of hose to connect them. Unfortunately the tight space required quick bends in the hose which restricted the flow. Initial tests showed the pump could easily empty the reservoir faster than the hose could fill it. The slip fittings were removed and a complex 1.5” pvc contraption was put in place of the hose. It was very difficult to measure all of the lengths and angles involved so many trial dry fittings were used. The pvc version turned out to be a blessing in disguise as it is much more functional than the hose in that it contains a valve and two quick disconnects. The valve allows the reservoir to be removed at any time. The pump is left running to empty the reservoir and then the pump is shut off and the reservoir lifted out of the pump house for maintenance.

The flag stone was installed using mortar cement. A double layer of chicken wire was arranged over the area. The chicken wire was folded over to give two layers. The flag stones were broken and test fitted a small section at a time. The mortar was applied and the flag stones were placed on top. Mortar was then added between the flagstones. This process was repeated as I moved around the pond. I completed half the surround on a Saturday and the remainder on the following Sunday. The job would go much smoother and faster if two people worked in parallel, one mixing mortar and one breaking and cementing the flagstones. I kept the mortar wet by misting it at frequent intervals to ensure a quality set.

The pond had to be emptied after installing the surround as some of the mortar fell into the water. The wet mortar makes the water unsuitable for fish.

The biofilter was installed behind the mound of dirt in the trees behind the pond in order to hide it. It was connected with a pair of quick disconnects at each end so it could be removed. My intention was to place the biofilter inside the house for the winter (along with the reservoir) as I didn't think the winter would be good for the inexpensive plastic.

The biofilter exit was connected to a length of pvc which simply hung out over the edge of the pond.

The pond was turned on. The valve from the pump had to be adjusted to prevent the biofilter from overflowing. The gravity feed from the biofilter was no match for the pump. Additional plumbing sprang to mind but would wait until the Spring.

Unfortunately other parts of the lawn had been trashed in the process. The landscaping around the house was covered with additional dirt from the pit, and the lawn around the pond had taken quite a beating.


The Pond - Take 2 - Winter Running.

By the time the pond was finished it was winter. I had a few fish in the pond that I wanted to try to keep in the pond over the winter. Dad has an enclosure that he erects over his pond in the winter. He uses electrical pipe tape to keep a section of his pond open and he leaves his small recirculating pump running. The idea is to let the pond ice over and form a thermal barrier allowing the deeper water to be ground temperature. A small area needs to be kept open to provide for gas exchange. I wanted to use the same electrical pipe tape but didn't want it to come in contact with the liner. So I built a pvc frame which would hold the heating tape below the surface of the water and away from the liner. It has a section which goes above the water level and allows several turns of heating tape to be used to keep a small area open.

We had an early cold snap in November. When the temperature dropped below freezing the pond ran without any problems. Ice formed on inside of the biofilter cover but as long as the water moved it didn't freeze. When December became cold again I winterized the pond. The reservoir inlet valve was closed and the pump emptied the reservoir. The pump was unplugged and the pump outlet valve was closed. The reservoir was disconnected and lifted out of the pump house. The pond was drained to a level below the inlet of the skimmer to prevent ice damage to the flagstone and the skimmer. The skimmer outlet assembly was disconnected from the skimmer and removed. The biofilter was uncoupled and the drain was opened to remove the water. The biofilter and reservoir were moved indoors. With the pond at the right level the heater assembly was lowered into the water and plugged into the pump house.

All in all the winter experience wasn't very good. Winds blew leaves, dirt, debris and snow into the pond. The pond froze and thawed many times over the winter, letting the muck drop into the pond with each thaw. It was obvious that either the fish should be wintered inside or a temporary enclosure should be placed over the pond.


The Pond - Take 3 - Spring.

In the spring I cleaned out the pond, reinstalled the pump house plumbing and reservoir and reinstalled the biofilter. All of these parts had wintered indoors. I filled the pond with water and turned on the pump. I waited several days for the chlorine to blow off and introduced a dozen large feeder goldfish. I then worked on fixing the landscaping around the pond.

A good waterfall requires a good flow of water. In preparation for an eventual waterfall I had wanted to increase the flow rate from the pump but had decided to wait the previous fall. The bottleneck was the biofilter which had only a 1” pvc, gravity fed discharge pipe. I could either increase the flow through the biofilter or bypass it all together. I decided the biofilter was fine as it was and installed a bypass to increase the flow rate.

I installed another pipe run which simply went around the biofilter and returned to the pond. I installed valves on both the biofilter supply line and the new bypass. The valves allow the amount of water going into the biofilter and bypass to be controlled easily. This turned out to be a great advantage. To service the biofilter I simply shut off its supply and let it drain, and the water can continue to circulate using the bypass. To adjust the flow into the biofilter I open the biofilter supply fully and adjust the bypass valve. There is much less resistance in the bypass as the biofilter water is forced through a spray bar.

The pond looked great now except for the two pvc return pipes. I decided that a quick fix would be to install a wooden trough to replace the pipes. I built the trough from three pieces of 2x6”, 8' cedar. I placed three one inch high blocks at intervals along the interior so rocks could be added without danger of them rolling down into the pond. I later purchased another piece of cedar and built a cover for the end so the pipes can't be seen entering the trough. This was a temporary fix to improve the aesthetics until a proper stream and waterfall could be built. But of course I've come to like the “spillway” and it won't be replaced any time soon.

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If I had to do it over again.

Of course I will get to create another pond when I move. The things I would do differently next time or would like to change on the existing pond when I find the time are listed below. Many of these items would simply make the pond more self sustaining, eliminating maintenance. A self sustaining pond is required if it will be left unattended for any extended period of time. (Just don't go on holiday.)

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This material is Copyright 1997 Craig Buchanan. All rights reserved. This page may be freely linked to.
Please send comments or questions to
mailto: buchananc@acm.org.