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Water Feature Knowledge Base - Need to Know (NTK)


is used to reinforce concrete. In ponds we usually use #3 (3/8" dia) rebar because it can be formed easily. We place the rebar on about 1 foot centers. More later.

Factors in a circulation system that contribute to feet of head, such as the length and width of pipe, the number of elbows and valves - as well as the size of the filter, or the presence of a heater, waterfeature, or automatic cleaner and the like.

Be careful of the rocks you select. Some rocks decompose quickly under water. Consult with your local rock supplier as to which they recommend. Also, take care to clean the rocks before you mortar them. We often use a local fieldstone that have mosses and lichens so we get a more natural appearance.

Normally we don't put rocks in the bottom of the pond. We don't do this because they cause dead spots. These stagnant, dead spots trap debris, and because there is no oxygen replenishing, an anaerobic bacteria colonize. This is the process that makes cesspools and high organic mud stink.

If you feel the need to put rock on the pond bottom, keep them well separated and put them in a bed of mortar. To fill in the voids, lay 1/2" thick bed of mortar and push 3/4" to 1-1/2" gravel in so that it is half way embedded in the mortar.



Why Salt Your Koi?

By Ben Plonski
Laguna Koi Ponds

Ordinary sodium chloride is probably the oldest fish medicine known to man. Salt can be very helpful for treating parasites; however it is not a cure-all. Most fish have an internal salt concentration of 1.0%. Tap water typically has close to a 0.1% salt concentration. An osmotic gradient exists between the fish and the water. The fish contain more salt than the surrounding water.
Through the process of diffusion the fish will lose salt and gain fresh water. In order to maintain proper cellular function, freshwater fish must constantly replace these lost salts and expel excess fresh water. This is called Osmoregulation and requires an energy expenditure. When salt is added to the pond the koi actually spend less energy osmoregulating. Energy may be saved for fighting disease. The osmotic balance of some parasites is upset by salt concentrations as low as 0.3% to 0.5%. Basically, the parasite’s cell dehydrates. This gives the koi a fighting chance.
Stronger salt baths of 2.5% for 10 minutes can quickly rid a fish of many parasites and bacteria or fungus. However, when the fish goes back into the pond, it may still be in a weakened condition and might fall prey to new parasites. This is why it is necessary to medicate the whole pond properly. Parasiticides or antibiotics may need to be added concurrently with salt treatments. Concentrations of salt stronger than 0.3% combined with formalin may be too harsh.
Salt has been used to control string algae at a concentration of 0.25% and higher. Killing large quantities of algae with salt may pollute the pond. Remove most of the algae by hand first to reduce pollution.
Salt concentrations of 0.3% are effective at detoxifying nitrite. The salt interferes with the nitrite ion exchange at the fish’s gills. Use until nitrites have cycled properly.
A 0.3% concentration is a good all around tonic for strengthening koi and improving disease treatments. This concentration will stunt your water lilies and string algae. You may choose to treat your fish in a separate container.
A 0.5% salt concentration has been proved scientifically to treat the “Ich” parasite. This concentration may be required for stubborn parasites like flukes. Fish can remain in this concentration indefinitely.
A 1% salt concentration is the same salinity as fish blood. This is called an isotonic solution. Salt does not transfer into or out of the fish’s body. Under normal pond salinity (0.1%), ulcer disease can cause a loss of internal salts through the open sore. Addition of 1.0% salt to koi in a separate hospital tank will limit this loss of internal salts. Limit this concentration to 2-4 weeks.
Always adjust salt levels gradually over 1-3 days to allow the koi time to adjust. Do not use salt continuously as parasites can become immune. The beneficial effects will be diminished. Use salt in the spring as a preventative for disease or when the koi are definitely sick. Monthly water changes will dilute salt to normal levels over time.
Much of the literature on salt treatment can be confusing. While we are given dosages in ppm, percent, ounces per gallon, grams per liter, etc., the most common term is percent. Percent is a comparison of weight of salt to weight of water, using 100 as a common denominator. Whatever dosages you measure, the units of weight must be the same. Following is a table of conversions to help you determine correct dosages.

Conversion Table
Tap water weighs: 1000 grams per liter; 8.3 pounds per gallon
Useful Conversions: 454 grams per pound; 3.78 liters per gallon

Solution % Grams/Litre Lbs./Gallon Results
0.0% (distilled water) 0 g/lr 0 lb*/100 gal fish die
0.1% (tap water) 1 g/l 1 lb*/100 gal  
0.25% 2.5 g/l 2 lb*/100 gal algae begins to die
0.3% 3 g/l 2.5 lb*/100 gal detoxify nitrite, good tonic for weak koi; some parasites
0.5% 5 g/l 4 lb*/100 gal parasites in pond 2-4 week treatment
1.0% (fish blood) 10 g/l 8 lb*/100 gal ulcers, antibiotics (4 week treatment in hospital tank)
2.5% 25 g/l 1 lb*/5 gal kills parasites, use as a separate bath, 10 -15 minutes
3.5% 35 g/l 30 lb*/100gal  


We use coarse aquarium sand in pressurized sand filters. You may put in 1/4 weight of clean pea gravel and the rest in coarse aquarium sand. see sand filter for how to install or clean sand.



is how the water exits the pond to the pump. One port is a pipe below the mouth of the skimmer to 6 inches above the bottom of the pond. The water enters the skimmer through both this port and through the skimmer mouth. The other pipe (usually the one in the back, below the equalizer) delivers the water to the pump.

Inside the skimmer is a floating weir and leaf basket. The floating weir adjusts to some changes in water level and helps take most water off the surface to aid in catching any floating leaves and debris. Below these are the float and equalizer. The ratio of how much water comes from the first port or over the weir depends upon the setting of these two doohickeys. The bottom of the float has a swing piece MORE installation

is can be installed before or after the pond is constructed. It consists of a black barrel with a leaf basket and floating weir. It is installed with 1-1/2" pipe (I often use ABS in the pond with black sides). It should be secured with weight so it doesn't jump when you put the pump on high. It needs to be mounted about 3-1/4" below water level. If you run the pipe over the side of the pond, you will need a check valve to prevent loss of pump prime. The check valve can be located in an horizontal or vertical run of the pipe in the pond.


Now is the big time. After all your hard work you are now ready to turn everything on for the first time. Nerves are on edge, champagne on ice.

  • Double check that all unions are tight.
  • Make sure the leaf trap at the pump is filled and the lid is properly closed.
  • Make sure the pond level is at the proper level.
  • Put Back wash valve (BWV) on backwash. If you have a valve on the discharge pipe, open it.
  • Before I flip the switch, I always say a prayer to the water Gods, big and small, whatever names they go by.
  • DO IT. Flip the switch. If you have a two speed, use the high speed. It may take some time to fill up the filter canister before water starts coming out the waste pipe. You may need to reprime the pump two or three times to get all the air out. If you have any problems, see Trouble Shooting.
  • Run it for 20-30 seconds after water comes out the waste pipe. We do this to wash out any debris that may be in the pond.
  • Turn off pump and change BWV to rinse. Run pump for 20-30 seconds.
  • Turn off pump and turn BWV to filter.
  • If you have a 3 way Jandy valve, turn it to waterfall.
  • Turn pump on and sit back and enjoy it. As you watch the waterfall, you may decide you want to make some small changes in the waterfall, see Waterfall Construction.



, also called bulkhead fitting, is used to pass through a liner without leaking. Each tank fitting is sent with instructions.

The sum of all resistances in a complete hydraulic system.


The period of time (usually hours) required to circulate a volume of water equal to the pool or spa capacity.





Ultraviolet germicidal energy is unmatched in its efficiency, simplicity and dependability for purifying water. Ultraviolet energy is radiation produced by low pressure mercury lamps. The lamps are made of a special glass, that allows the passage of UV light rays. This radiation is capable of killing all micro-organisms that it comes in contact with. UV rays strike bacteria, algae and protozoa breaking through the organism's outer membrane . The radiation reaches the DNA of the organisms, causing abrupt modification bringing about their destruction quickly and effectively.



    There are several key factors that determine the performance of ultraviolet sterilization. The first is "lamp life." Major germicidal lamp manufacturers recommend that when a lamp has reached its 60% efficiency it should be changed. What is often overlooked, is that different lamp styles reach their it's end of useful lamp life after different amounts of time. For example, the G30T8 style lamp with JAPAN etched on it reaches it's end of useful lamp life after 2500 hours of operation, while the Phillips Long Life G30T8 reaches it's end of useful lamp life after 8000 hours. The GPH/T5 style lamps used by Emperor Aquatics are superior to the commonly used T8 lamps. The GPH/T5 lamps provide more UV energy as well as giving 9000 hours of operation before reaching 60% efficiency.

    The next important factor in ultraviolet sterilization effectiveness, especially when considering a commercial application, is the design of the unit itself. Ultraviolet sterilizers that incorporate the use of more than two lamps should have the lamps housed together in one vessel. This multiple-lamp/one-vessel design dramatically increases the UV energy when compared to the inferior single lamps which run parallel in a series (many lamps in single vessels). The multiple-lamp/one-vessel design increases valuable UV energy without restricting flow capacity (as with the single lamp/single vessel parallel design).

    The amount of water forced through an ultraviolet sterilizer ultimately determines the dosage of radiation absorbed by the mi(cro organisms passing through it. Emperor Aquatics' recommended flow rates are based upon our lamps when operating at 60 % efficiency. See UV lights for suggested maximum flow rates. It is very important that our customers fully understand this information so that they receive the results they expect. In contrast, other UV manufacturers choose to give very little information covering flow vs. dosage ratings for the equipment they sell, creating a great deal of confusion and misbelief about UV sterilization and its legitimacy. Emperor Aquatics knows that ultraviolet sterilization is a very viable method of disinfection, when the user is supplied with a dependable, properly designed unit.

    Emperor's UV lamps are always positioned between the water inlet and outlet ports, using all of the UV lamp's length and available UV energy to sterilize the water (kill algae). Our UV Sterilizers are the only units featuring our exclusive easy-service quartz sleeve module and large internal view ports for monitoring the condition of the UV lamp. All of our units feature unionized water inlet and outlet ports for ease of service. All of our units feature long life (9000 hour) T5 hard quartz glass UV lamps for maximum performance and longevity. All of our unit's housings are molded in a black UV-resistant high-density plastic with a lifetime warranty against failure of the plastic due to UV light exposure.

Ultraviolet lights, like pumps, come in two main types, submersible and out-of-pond. Submersible UV lights are installed after the submersible biofilter if there is one. They can be either before or after the submersible pump. They need to be plunged or hard wired into a GFI.

Out-of-pond UV lights can be installed in two different ways depending upon pump flow rating and UV light flow rating. If they are the same, or close to it. The UV light should be in line after the sand filter. If the flow of the UV lights rated much lower than the pump. Install a Jandy 3-way valve after the sand filter. (Remember you can change the input side of the valve for easier installation. See Jandy valve)

Have one discharge leg go to the UV light. After the water passes through the light, it can join the remaining water with a PVC tee or a PVC wye. If you want to, It is easy to make a rack for the UV light out of 3/4" or 1" PVC pipe and fittings.

We recommend that for two speed pump installations, install UV light in the manner just mentioned, Rather than have the two discharges come together again, have the water that passed through the UV light return to the pond via the venturi and have the other return go to the waterfall. The majority of the time the pump will be on energy efficient low speed yet the pond received maximum effect of the UV light and the venturi. The occasional times when the waterfall is wanted the water won't go through the UV light but would not be very effective because the water flow rate would be too high.

is backing we put in the hole to protect the liner from sharp rocks, etc. Some people use old carpet pad or carpet. We don't want to take the risk of missing a staple and having problems. We do sell underlayment but you can go to a building supply house and ask for Mirifi or any other heavy drain material.

Unions are a PVC fitting that can be unscrewed and re screwed holding two sections of pipe or pump and pipe, together. Often they are used on both sides of the the pump, filter and UV light so that the system can easily be opened if repairs or cleaning are needed.



is a pain in the backside but still the best way to keep stuff from accumulating on the bottom of the pond. Whether you have a 2 port skimmer or a nicheless skimmer, the idea is the same. The reason I don't find it enjoyable is that there are, in my opinion, no good adapters between the inlet pipe to the pump and the vacuum hose. With a 2 port skimmer,

  • Pull out skimmer, leaf basket and equalizer float
  • Use a 1-1/2" threaded plug to close the inlet from the bottom of the pond.
  • Put the circular adapter plate in the bottom of the skimmer. With the hose full of water stick it on the end of the adapter and start vacuuming. With a 2 speed pump, start on low speed.
  • Backwash the filter thoroughly.


Ball valves are generally only used in the open or closed position. In water features, we use ball valves if the pump is below the water level so we don't lose water when we clean the leaf basket.

A check valve allows water to go one way in a pipe but not the other way. We recommend, and sell, only the flap type check valve where the flap moves out of the way entirely. Another kind of check valve has a piston and spring inside and restricts flow a lot more and can catch string algae. We sell check valves with, and with out, unions. A union allows you to easily clean it and change direction if you put it in wrong.

Make sure the arrow on the check valve that indicates the flow is pointing the right way. If you are putting horizontally, the hinge needs to be up. If the pump is higher that the water level, you need a check valve before the pump to prevent losing prime when you open the system. The check valve can be anywhere in the intake pipe as long as it is below water level. Generally we use a check valve on the pipe going up to the waterfall. Also, if the pump is lower than the water level, you need a check valve on the return to the pond so the pond water doesn't come back through the filter and pump

are useful in controlling the water to the waterfall or a direct pipe back to the pond. People do this to save energy, minimize algae on the waterfall and decrease water loss through splash and evaporation. These valves have one inlet and two discharges i.e. waterfall and venturi. Nice things about these valves are that they can't shut off the flow completely. All they do is direct the flow, not restrict it. Also, the balance can be changed so that the exact amount of water goes over the waterfall. We usually recommend the pipe back to the pond have a venturi.

NOTE: The valve is a 'tee' shape with the water entering the stem of the tee and is discharged through the cross bar. It is possible to unscrew the 8 screws and move the top so that the water enters one side of the cross bar and exits through the other and the stem. Try to arrange it so the larger flow goes straight through. This can make installation much easier.


Aerates the water as it returns to the pond. It is a small PVC part that restricts the water flow so that a low pressure occurs behind it. Air is sucked down through a small pipe and mixed with the water. It should be placed no more than 18 inches below the water level. It does create some sucking noise but can be adjusted by adding a valve to the 1/2" air inlet.

It need not be located near the pond but the further away the larger, and noisier the bubbles will be. It is best to put a union in front of it should you want to add or remove the inserts to increase of decrease the vacuum.

Often we hide it in the rocks around the edge for easy access. Use a tank fitting to go through the liner.



A pond and a fountain are very different in their construction and their operation. A fountain can be treated similar to a swimming pool. A fish pond on the other hand is more like a big, very big, aquarium. With a pond , we are not able to dose it chemicals like we could a fountain. A pond is a live organism and the water is like the air we breath.

There are several factor regarding water to be addressed. Water quality and water clarity are not the same thing. Fish can live well in pea soup conditions but crystal clean water can be potentially lethal.

A gravity filter works much the same way but are a bear to clean and thus often are not cleaned regularly


Here in northern California, we keep our pumps in operation all year long. Where I grew up upper Midwest, more stringent wintering is necessary.

  • Turn off all power. If you have a dedicated circuit breaker, turn that off also.

Open the drain plugs in the bottom of the leaf trap, pump, filter and other elements of the system so that no water is in the system that may freeze and expand and damage the works. If you can easily remove the pump entirely, it may be worth storing it in the garage or safe place.

Fish can usually winter over well if the water does not freeze solid. There are pond heaters available. If you need help locating one, contact us and we'll locate one for you.


X, Y & Z

Some of you old hippies may recognize, and remember, the adaptation of this title from a book expaining how to 'become one with your motorcycle' in order to repair it. While building a cascade or waterfall, it is essential, and fun, to think like water. For our purposes, we consider it a waterfall when the water actaually falls.

A cascade is more like a stream where the water tumbles between and around rocks but never actually loses contact with the water. If during the design and construction,[1] you put yourself in place of the water, you visualize, and even feel, how the water will behave in order to have an end product of which you can be proud. This is especially important to be Zen with your water as you place each and every rock.

Ususally we start building the waterfall or cascade from the bottom up. As you dry set the first rock, envision how the water will react to the rock. If the rock is in the corner, it may not have any contact or effect. But, you may need to place rocks on top of this one. How will those rocks effect the water?

Does it spread out the water or focus it to one side or the other? Generally, we need to have the rocks on the sides of the cascade guide the water back toward the center. In the middle of the cascade, we can utilize several types of rocks based on their effect. A good water feature is usually a mix of all these effects.

  • Sentry rocks, often large rocks at the top of the waterfall, focus the water toward the center.
  • Dividing rocks divide the water wo water goes around both sides.
  • Spillway rocks are usually flat stone that create the waterfall.
  • Splash rocks catch the water after it falls causing it to splash.

HINT: Something to avoid is to have a riser and waterfall, then another riser and waterfall etc. For some reason many beginners think of this stairstep effect as a natural waterfall. WRONG.

is my attempt to get you to try to 'be the water' as you design, layout and build a waterfeature. If we can put ourselves in the water's place, we can design and build a water feature that is in balance, balance being the essence of pleasure.

We need to design a water feature in balance with the surrounds. For example, we don't want a big, loud waterfall in a small backyard. On the technical side, we need to design the equipment so they are balanced, that is the pump, filter, UV light and all the components are properly sized.

During construction, we want to locate the equipment in a balanced or 'logical' order. I define logical order as being able to avoid a lot of unnecessary fittings. If the plumbing configuration is simple and works, it was probably done in balance. If, on the other hand, it is very hard to follow the pipes as they spaghetti in and around and include a lot of sharp bends, the system is not in balance, nor efficient, nor pretty. Believe it or not, plumbing, like anything else, can be pretty. Take pride in your work.



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