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Water Feature Knowledge Base - Need to Know (NTK)


The resistance in a hydraulic system based on the equivalent height of a column of water that causes the same resistance (100 feet of head equals 43 pounds per square inch.)

A pressurized sand filter is an integral part of biological filtration. They act both as a mechanical and biological filter. Not only do sand filters trap 'stuff' on top of the sand, they colonize bacteria on the surface of the sand that eat the nutrients in the water that would otherwise build up and become toxic to the fish. See nitrification. We favor pressurized sand filters and 6 position back wash valves over gravity filters because they are space efficient and are much easier to maintain and clean.

Sand filters are basically a canister with laterals, (slotted pipes) near the bottom and a diffuser near the top. Attached to the canister is a 6 position back wash valve that directs the movement of the water. The function of the back wash valve and the movement of the water are described in the back wash valve section. Often connected to the canister is an air bleeder valve, pressure gauge and bottom drain.

We have selected Sta Rite and Purex Triton TR sand filters because these filters are reliable, economical, easily back washed and are space savers compared to gravity filters. They are the same kind of filters that are used for swimming pools. Both have similar design with the exception that some of the Sta Rite filters split apart in the middle whereas the Purex Tritons do not. NOTE: We use clean course aquarium sand or the first 1/4 the volume in clean pea gravel and the balance in clean course aquarium sand.

Some people think that a sand filter is unnecessary and that a pond will function well 'naturally'. This may work for a while but eventually, in our opinion, this is short sighted thinking. Firstly, these ponds are not 'natural' and never will be. Secondly, watch a natural pond over time and see if that is what you want to happen to your pond. They fill up and become a bog and eventually a meadow. A pond, like a house or other landscaping, needs regular maintenance to keep them up. Some people can live in a house without taking out the trash for weeks or longer. I can't. Not being able to get rid of excess nutrients in the pond water is the dangerous for the fish and leads to a very unsightly pond. See pond overview.

Our idea is to have the best equipment available to maintain a healthy, esthetically pleasing pond with a reasonable amount of maintenance. Also, we think it is easier, and better for the pond, to maintain a pond a little at a time and not try to dig out, literally, a pond that has been ignored for years. An important part of having a healthy pond is to have the right size sand filter.

The effectiveness of the filter is largely a factor of how fast the water passes through the sand. The slower the water moves, the more material can be filtered out. If you have a big pump and small filter, the water will move so fast, you could pass golf balls through it, almost. Having the correct size filter is probably your biggest ally to maintaining a healthy pond.

The size of the filter is determined by the number of gallons in the pond and the number of fish and plants anticipated.Once you have determined how many gallons there will be in the pond, select a filter that can handle that many gallons every two hours. For example, if you have a 8,000 gallon pond, you will need a filter that can handle 4,000 gallons/hour or about 67 gallons/minute. If you are on the border between sizes you are better off going with the bigger size to keep the flow rate down.

See Pump and Filter sizing.

Each filter comes with directions from the manufacturer. We encourage you to lay out all the equipment; pump and leaf trap, sand filter and back wash valve, UV light and Jandy 3 way valve (if needed) before you start cutting and gluing. See pump/filter schemata and PVC pipe gluing and Zen and the Art of Plumbing.

The sand filters need to be set on a firm base of crushed gravel, concrete cap blocks (1-1/2"x8"x12") or a concrete pad. If the native soil is susceptible to settling when wet, the dirt should be removed and replaced with compacted rock such as crushed shale. Some of the bigger filters will weigh over 1400 pounds when in operation.


Mount the Back wash valve (BWV) on the side of the filter. (Hand tighten only.) Lay out the pump, filter and ultraviolet light. Different back wash valves have different configurations. Keep in mind where the pipes will go. You want to keep the pipe from the pump to the filter as simple as possible. We can usually do it with only two 45° fittings. Remember, we want to keep the piping as simple as possible using only as many 45° elbows as necessary and as few 90° elbows as possible. Many pumps come with unions. If your pump doesn't, be sure to put a union between the pump and filter. See PVC cutting and gluing for more hints.

Yet again, depending upon the backwash valve, it may have a female threaded fitting or a slip fitting. With a threaded fitting, you can use a male fitting, a male threaded 90° elbow, a threaded male union or cut an end of a PVC nipple to thread in the opening. Remember, think in 45°s, not 90°s when possible. See Zen and the Art of Plumbing. Connect the BWV to the return pipe with a union. The return pipe then may go to a Jandy 3 way valve if there is one pipe directly to the pond and another pipe to the waterfall. The waterfall is usually higher that the filter and it is necessary to put a check valve in the pipe so we do not drain the pipe every time we open the leaf trap by the pump. If you are using a Jandy three way valve, install the check valve after the Jandy. See Pump/Filter schemata.

Again, we want to use as many 45°s as necessary and the fewest 90°s. If there is a lot of spaghetti in the piping a lot of action during back washing would be lost.

It is good insurance to put a ball valve in the waste pipe to insure that no water is lost. If you are using a 1-1/2" BWV and the run is greater than 15', think about upgrading to a two inch pipe.

You are ready to put sand in the filter.

These generalized instructions are written for the filters that have a hole in the top of the filter. The same instructions apply for filters with a split housing.

  • Check to see that laterals are hand tight. Do not over tighten. If the lateral are slotted on only one side, the slots should face downward for maximum filtration.
  • Fill filter with 12" of water above the laterals. This helps prevent damage when you put in sand.
  • NOTE: We use coarse aquarium sand or the first 1/4 of volume in pea gravel and the remainder in sand in pond filters.
  • If the diffuser in the hole of the filter has a little air relief tube with a screen on it, remove it and don't step on it. Move the diffuser aside. We wash all the gravel and sand with a kitchen sieve in a bucket of water to remove the small sand that can, and will get stuck into the laterals requiring removal of sand. An ounce of prevention is worth avoiding a dirty job. Be sure not to get sand in the diffuser.
  • Put in the sand slowly to insure you don't damage the laterals.
  • Use the amount of sand recommended. The sand should come up approximately to within 2-4 inches to where the filter starts to get smaller at the top.
  • When all the sand is in, move it around by hand to level it out.
  • Move the diffuser back to the middle of the hole and replace screen.
  • Prepare the dome or upper filter housing by putting on pressure gauge and air relief valve if provided. Instructions provided with each filter
  • For a 'hole-in-the-top-filter, put the 'O' ring on the male threads of the dome and lubricate with silicon lube. Make sure threads on filter are clean and lubed. Screw down dome using wrench provided.
  • For a split-body filter, put the gasket around the lower filter housing. Place upper housing in place. Install compression band or fittings. No lube is required.

After a few years, most sand filters require cleaning. If you are experiencing volume loss that is not improved very long by back washing, the problem may be there is a lot of gunk and caked algae collected on top or in the top layer of the sand. Double check to see if the volume is restored with the BWV on 'recirculate'. If it is, it's time to clean the filter. Wear long sleeves so you don't get fiberglass from the filter opening on your upper arm. See Trouble Shooting for more help to determine volume loss.

Before we talk about filter cleaning, let me tell you a little story in the book Continuum Concept by Jean Liedloff. The author relates an incident she saw when taking pictures of Gringos and Indians working together to portage heavy canoes up a creek. Both the Gringos and Indians were slipping, scrapping and getting beat up by the experience. What she observed was the Gringos were cussing at the pain and discomfort while the Indians were laughing at it even though they were experiencing the exact same thing. This may be one of those jobs to remember to laugh at. It doesn't get better by cussing. Actually its not that bad, but its a good story anyway. It is made a lot easier with a Pac-Fab Sand Vac.

If you have the proper size sand, there is no point in getting new sand. We just need to get the sand out of the filter, clean it and replace it. Once it is out, it is easy to clean and expensive to replace. How difficult or easy the job is depends upon the type of filter you have. For all filters, make sure power is off and open air bleeder valve or otherwise depressurize filter. Move Back wash valve to closed. Bring out a radio and put on some good tunes.

For those of you with a split-housing filter it is relatively easy to loosen the compression band and remove the upper housing. Then scoop out the sand using a plastic container. Skip to Lateral Removal.

For a hole-in-the-top-filter, there are two or maybe three ways to remove the sand. The sand can be removed through the hole by scooping of siphoning if your have a sand siphon. With the newer Triton filters by Pac Fab you can remove the housing for the drain plug but this is very messy especially if you want to reuse the sand.

Scooping - Wear long sleeves. Remove the dome and the little screen and move the diffuser aside. Don't get sand in it. If there is a bottom drain, you may be able to drain out the water. Often they are clogged. You can either scoop out the water or siphon it out with a tube or garden hose. Use a plastic glass, yogurt container, etc. to scoop out the sand.

Siphoning - Wear long sleeves. Now we use a sand vacuum which hooks up to a garden hose and siphons out most of the sand. The lower you put your buckets, the more sand you can get out. If you have someone to help move the siphon for bucket to bucket so that you don't have to turn off the water to move it, you can siphon out almost all of the sand. Put the sand in buckets or a wheelbarrow.

Draining - The newer Pac Fab Triton filters have a 2" sand drain located at the base of the canister. The drain plug is located in the sand drain. You can remove the drain plug and then the sand drain. I recall that the threads are reverse so you turn it to the right. If the sand is really caked it may be necessary to get into the filter with your hand or garden hose to loosen the sand.

Using the sand drain to remove the sand is messy. You may be able to allow it to flow in some low pans.


  • As you remove the sand, you will encounter 8 or 16 laterals about 6 inches above the bottom of the filter. Remove them carefully by turning them counterclockwise. If you have a TR140 or short arms, it may be helpful to rotate the lower pipe assembly to which the laterals are attached. Clean the lateral with a brush such as an old toothbrush.
  • Replace the laterals. If they have the slots on only one side, have them facing downward.



The volume of liquid flowing past a given point in a specified time period. Usually expressed as US Gallons per minute (gpm).






(Ground Fault Interrupter) is a safety feature that is found in most kitchens and bathrooms or anywhere near water. A circuit breaker trips when the temperature gets too high and takes a few seconds to trip. A GFI, on the other hand, trips when there is a slight loss of current and trip much faster than a circuit breaker. Some circuit breakers are GFI as well but have a reputation as sometimes being unreliable. All pumps and lights should be GFI protected.

All pumps and 120v lights need to be properly grounded. For pump, we usually drive an eight foot copper-coated steel rod into the ground and attach it to the grounding terminal on the outside of the pump. This connection is made with a grounding clamp and #6 bare copper wire. Follow all local codes.

All lights need to be grounded. Light canisters for gunite (concrete) all have grounding lugs on the outside. The lugs are connected to the rebar with bare # 6 copper wire. In addition, the lights themselves have grounding wires that need to be connected to a GFI.



is a unit for measuring the power of motors, engines and pumps. It is equivalent to 746 watts. That is to say, running an one horse power pump takes about the same electricity as turning on seven 100 watt and one 50 watt light bulbs. Therefore, using the Sta-Rite JW two speed 1/8-3/4 horse power pump take about the same juice on low as a 95 watt light.

Not all horsepowers are equal. All pumps now come with something called 'service factor'. Officially, the service factor indicates the degree to which as electric motor can be operated over a specified horsepower without danger of overload. Unofficially, its a fudge factor to make a 1 hp pump look like a 1.5 hp pump. A 1 hp pump with a service factor of 1.65 is exactly the same pump with the same output as a 1.5 hp pump with a service factor of 1.1. The only thing differant is the number on the name plate. Because of the confusion, many companies are forced to carry both of the pumps in different packaging.

Beware of the fast sales person that says they can sell you a 1.5 hp pump for the same cost as a 1 hp one. Check the service factor and if he/she/it is trying to get a fast one past you, return to the reputable dealer.

All of our pumps have a the highest service factors available. That means they have more in reserve and are maxed out all the time.

We can not order a pump on horsepower alone. We need to be concerned with how much water the pump can put out at the hydrolic head we anticipate.

is the study of the movement of water and its applicatons. We will write more about this as time allows. Hydrology is the theoretical basis by which we select pumps, filter, design and about everything else concerning a pond or filter. Examples: As discussed in Pipe Size, we are limited by the laws of hydrology as to how much water we can pass through a pipe. Also, if we are going to use two bottom drains in a pond, we have ways of plumbing them to get a balance flow between the two naturally. We know of a really good training in hydrology for swimming pool people that is very relevant for us fountain and pond people. Contact us if you are interested.



The rotating part of a centrifugal pump that creates the flow of water.

as described in Trouble shooting, if the water volume does not improve with the back wash valve on recirculate, it may be that the impellor is clogged. Cleaning the impeller is more often necessary if the pond is under pine trees because the needles can get through the leaf baskets.

  • Make sure the Pump is turned off, BWV on off
  • Undo union in front of the pump and loosen union on discharge side of the pump. Don't loose the 'O' rings. If there are no unions, you may want to install some.
  • Open the impeller housing either by loosening the retaining band or undoing the six bolts that hold the housing together.
  • Split the housing apart
  • Clean the debris with needle nose pliers or tweezers. Make sure it moves freely. Hose everything down.
  • Make sure 'O' ring or gasket is clean and in place with light lube and close it back up.

If you need to remove the impeller, follow the instructions for impeller cleaning

  • open up the electrical cover and place a wrench (often 3/8")on the shaft and loosen the impeller by hand. They usually are counterclockwise (normal) thread and you have to crank on it.






A Koi Pond
Landscape Smart : Home and Garden Television, Episode LDS-306


Step One: Preparing the Site

The back yard of David and Judy Blake's San Francisco home features a beautiful expanse of lawn but doesn't offer much in the way of visual interest. To add color and aesthetic appeal to the site, the couple has decided to add a koi pond in the area near the back patio.

To implement the project, the Blakes enlist the help of contractor Jim Wilder, who says water gardens offer a number of benefits, chief among them soothing sound and tranquil beauty. Wilder estimates that a professional installation would cost around $7,000 (using a sophisticated pump and filter system such as the one used here), whereas the average do-it-yourselfer can expect to spend about $2,000 for the required materials. Wilder also explains that the project requires a great deal of physically challenging labor and the average homeowner would need about four weekends to complete the work. On a difficulty scale of 1 to 5, with 5 being the hardest, Wilder rates the project a 5.

To get started, the crew first clears the area where the water feature will be located. Once the workers remove the turf, they use landscaper's marking paint to outline the shape of the pond and the cascade that will provide the structure for the waterfall . (A gently rounded shape gives the pond a natural look; Wilder recommends avoiding straight edges.)

Next, the crew digs the hole for the pond to a depth of 2 1/2 feet, carefully following the outline. All ponds with fish must be dug at least 2 1/2 feet deep: predators pose a threat in more shallow water. The dimensions of the pond measure about 10 feet by 12 feet.

Crew members build up one side of the pond--topped with a few stones--to compensate for an existing slope. This will create a level bed for the water once the pond is filled. Then they dig out a ledge along the perimeter of the pond, about two inches below where the surface of the water will reach. This will serve as a starting point for building up the stones.

Finally, the crew digs a trench from the pond to the top of the cascade. Inside the trench workers lay a 1 1/2-inch length of PVC pipe (sold in home centers) that reaches from one end of the trench to the other. This will allow the water from the pond to be recirculated to the top of the cascade. Wilder notes that this is a good time to lay any low-voltage power lines that will be used for lighting as well as the electrical line to power the pump.

Step Two: Lining the Pond and Adding Plants

For this project the crew uses a professional-grade external pump (and filter), which is stronger and easier to maintain than other types of pumps. Homeowners who want to keep costs down and keep the installation relatively simple may prefer a submersible pump. Wilder notes that submersible pumps have a relatively low usage cost--about $5 a month when running full time.

After installing the pump and filter, the crew begins lining the pond . The first step is to remove any rocks or sharp objects that could puncture the liner. Next, the crew lays landscaper's cloth (available in home-supply stores) and cuts a hole to accommodate the end of the return pipe.

Crew members then attach a bulk head fitting (available in pond-supply stores) to the end of the pipe where it emerges from the fabric: this permits the liner to be sandwiched next to the landscaper's fabric to prevent leaks.

With the landscaper's cloth in place, the crew lays a layer of sand over its surface to hold it in place. Then workers begin laying the liner, made from a heavy PVC material that costs about $1 per square foot and can be found in home-supply stores. The crew lays the liner so it covers the entire pond, with enough excess hanging over the sides so it won't be pulled too small when the rocks are put in place. Now the workers add water to the pond to fill the liner and weigh it down.

Finally, they cut a hole in the liner to allow the return pipe to emerge and finish attaching the bulk head fitting, making sure it's secured tightly.

While the crew finishes adjusting the liner, garden designer Dorothy Nickolai sets to work on the planting plan. Nickolai says her goal is to add color and interest without overwhelming the area. She explains that the plants will create a setting for the pond that helps integrate it with the surrounding garden.

Inside the pond Nickolai adds several water-loving plants for strong visual impact, then plants a variety of colorful, low-growing shrubs and grasses around the pond's perimeter (all the chosen plants are suited to a pond setting). Featured plants include the following:

  • Hibiscus moscheutos, Zones 5-10
  • Cardinal flower (Lobelia cardinalis), Zones 4-8
  • Waterlily (Nymphaea 'Hermine'), Zones 4-11
  • Dwarf red canna, Zones 8-11
  • Zephyr lily (Zephyranthes candida), Zones 9-10

Note: In colder climates, the dwarf red canna and zephyr lily should be brought indoors during winter.

Step Three: Setting the Stones

Wilder has chosen Sonoma fieldstone from which to construct the pond. He explains that it is local to the area, is inexpensive and has a great texture, covered with mosses and lichens that will enhance the pond's natural look. The stone's appearance is similar to that of stone used in other areas of the property, which will help unify the pond with the landscape.

Wilder explains that it's important to select stone that will hold up well underwater. He recommends checking with local building-supply stores to find a suitable type.

The crew begins building up the stones from the ledge inside the pond, working upward. Wilder explains that it's a good idea to work in small sections to avoid getting too far ahead without evaluating the pond's appearance. He also recommends avoiding straight lines when laying rocks in place to maintain the natural look.

Next, the crew moves on to the mortar, mixing it with dye so that its color blends better with the rocks. (Mortar dye is available in most hardware and home-supply stores.) Wilder says the consistency of the mortar should be just thick enough to adhere to the rocks. Wilder suggests using small pieces of rock or cinderblock as supports to prop up larger stones and help wedge them into place.

Once the ledge is in place, the workers move on to the cascade--first building up the walls, creating a curving path to give the water a natural flow. They integrate several flat stones into the cascade to serve as "spill stones": these will create mini-waterfalls along the cascade and into the pond. The spill stones must be level to ensure that the water flows properly.

To fill in between the rocks and hide any areas of exposed liner, the crew uses 1/8- to 1/4-inch Mexican gravel mix, available in rock and sand specialty stores. To hold the gravel in place, they first add additional mortar around the stones that are already laid, then sprinkle gravel over those areas and pat it down.

After allowing the mortar to set for about two days, the crew fills the pond with water to check for leaks. Once the pond has been deemed leak-free, workers treat the water with dechlorinating chemicals to remove chlorine and chloramine, both of which are poisonous to fish. Now they're ready to add koi.

Step Four: Adding Koi

Koi expert Bob Gordon says koi are ideal for a backyard pond because they're beautiful and playful and can be hand-fed. When selecting koi, Gordon advises looking for active, fast-swimming fish that are integrated with the others; avoid fish that are isolated as well as any with signs of injury such as split fins.

Koi, which generally range from four to five inches in length, cost about $20 apiece and can live to be more than 100 years old. He also notes that the fish will eat floating koi food but are easily overfed because they like to nibble all day. As a precaution against overfeeding, give the fish just enough to eat for a four- or five-minute period. Koi generally eat more in warmer temperatures, less in cooler temperatures. Finally, Gordon explains that koi should be brought indoors and kept in an aquarium during winter in climates where temperatures drop particularly low.

Bob Gordon
Koi Expert, Pond Systems
320 Tesconi Circle
Santa Rosa, CA 95401
Phone: 707-579-6070
Email: Pondsys@PondSystems.com

Dorothy Nickolai
Garden Designer, Dorothy Nickolai Garden Design
646 Oregon St.
Sonoma, CA 95476
Phone: 707-996-1086
Email: djnick@vom.com

Jim Wilder
Landscape Contractor, Living Water Creations
PO Box 611
Santa Rosa, CA 95402
Phone: 707-527-0125
Website: www.pfpros.com


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