Pond-Free 101 Chapter 7
Pumps in Reservoirs, with recommendations
Circulation is important in Pond-free systems, but for different reasons than in pond ecosystems. Ponds require constant circulation to avoid stagnation and maintain oxygen levels for plants, fish and other animals. Pond-free systems don’t need to support aquatic life, so they can be turned on and off at will, but the waterfall is the whole show, no lilies or fish to look at, so it has to be impressive. Pond-free water features typically have a much larger ratio of waterfall size to reservoir volume, so the operating costs of the pump or pumps powering that large waterfall can be a consideration. The hidden reservoir keeps evaporation losses low, but every silver lining has a cloud – without being able to see the water level, it’s pretty easy to lose track and run the pump in low water, which can quickly lead to overheating and premature burnout, especially with vertically oriented pumps. The combination of powerful pumps and hidden water levels leads to a few logical recommendations.
- In general, the deeper the water is above the pump, the better. Locate the pump as low in the reservoir as possible. Some manufacturers make their Pump Vaults taller than their Matrix Blocks for precisely this reason – Atlantic, for example. That way you can set the bottom of the Vault 4-6 inches lower than the height of an installed EcoBlox, to give the pump a few more inches of freeboard (and to serve as a cleanout for sediment), while the top of the Vault still lines up perfectly with the top of the reservoir. Be especially careful with half-height or shallow Matrix Blocks, as they encourage the construction of shallow reservoirs that can exacerbate the problem of pump burnout.
- Maintain the water level well above the pump. Water level is
going to vary because of splash and evaporation losses, and few folks have the time or inclination to remove a rock or cover and visually check the water level as regularly as necessary. The easier way to maintain the level without personal attention is to set an Automatic Fill Valve 6-12 inches above the top of the pump, so the water level can never drop too low. Autofills like the AF-1000 need a ¾ inch hole and a water supply, through either ½” poly sprinkler or funny pipe or even a garden hose. Just be sure the feature isn’t leaking before turning on the autofill, or it may hide potentially large water losses. 
If an autofill valve isn’t an option, protect the pump with an electronic Pump Protector, a switch that monitors the current going into the pump for any changes in load or draw, then shuts the pump down before it can overheat. Because the switch activates before any damage can occur and requires a physical reset, the problem will usually get noticed and, hopefully, get fixed. Regardless, unlike with thermal switches, the pump never overheats.
- Use horizontal pumps in shallow reservoirs; reserve vertical pumps for deeper reservoirs. A common problem occurs when a powerful, vertically-oriented direct drive pump operates in shallow water. When water levels drop the pump will continue to push water well after the top of the pump is above water level. All the electronics live in the top of the pump, and when they overheat, it’s the beginning of the end, even with internal thermal switches that shut the pump down as it overheats. Underground, unmonitored, the pump will cool, the switch resets, and the cycle starts all over again. After a certain, very finite number of cycles both the switch and the pump will burn out. In general, while most direct drives are vertical, most Asynchronous Pumps are horizontal, so as soon as water levels drop to the level of the top of the pump they start sucking air, signaling a problem before they get a chance to overheat, and they are arguably less susceptible to low water damage, though any submersible pump for water features needs to be fully submerged. Asynchronous pumps are also very efficient and available up to around 8000 GPH; the use of multiple Asynch pumps can provide as much water as a big direct drive at a lower electrical cost. Visit the College of Pumps for more detailed information!
- Finally, use check valves to keep debris out of pumps. The tubing coming out of the pump offers direct access to the impeller inside the volute. Without a check valve, any pebble or debris at the top of the falls that gets sucked down the pipe when the power goes off will end up right where you don’t want it, inside the volute, ready to snap an impeller vane when the power goes back on. Check valves are cheap insurance to keep anything from going where it doesn’t belong.
Circulation is important in Pond-free systems, but for different reasons than in pond ecosystems. Ponds require constant circulation to avoid stagnation and maintain oxygen levels for plants, fish and other animals. Pond-free systems don’t need to support aquatic life, so they can be turned on and off at will, but the waterfall is the whole show, no lilies or fish to look at, so it has to be impressive. Pond-free water features typically have a much larger ratio of waterfall size to reservoir volume, so the operating costs of the pump or pumps powering that large waterfall can be a consideration. The hidden reservoir keeps evaporation losses low, but every silver lining has a cloud – without being able to see the water level, it’s pretty easy to lose track and run the pump in low water, which can quickly lead to overheating and premature burnout, especially with vertically oriented pumps. The combination of powerful pumps and hidden water levels leads to a few logical recommendations.
- In general, the deeper the water is above the pump, the better. Locate the pump as low in the reservoir as possible. Some manufacturers make their Pump Vaults taller than their Matrix Blocks for precisely this reason – Atlantic, for example. That way you can set the bottom of the Vault 4-6 inches lower than the height of an installed EcoBlox, to give the pump a few more inches of freeboard (and to serve as a cleanout for sediment), while the top of the Vault still lines up perfectly with the top of the reservoir. Be especially careful with half-height or shallow Matrix Blocks, as they encourage the construction of shallow reservoirs that can exacerbate the problem of pump burnout.
- Maintain the water level well above the pump. Water level is going to vary because of splash and evaporation losses, and few folks have the time or inclination to remove a rock or cover and visually check the water level as regularly as necessary. The easier way to maintain the level without personal attention is to set an Automatic Fill Valve 6-12 inches above the top of the pump, so the water level can never drop too low. Autofills like the AF-1000 need a ¾ inch hole and a water supply, through either ½” poly sprinkler or funny pipe or even a garden hose. Just be sure the feature isn’t leaking before turning on the autofill, or it may hide potentially large water losses. If an autofill valve isn’t an option, protect the pump with an electronic Pump Protector, a switch that monitors the current going into the pump for any changes in load or draw, then shuts the pump down before it can overheat. Because the switch activates before any damage can occur and requires a physical reset, the problem will usually get noticed and, hopefully, get fixed. Regardless, unlike with thermal switches, the pump never overheats.
- Use horizontal pumps in shallow reservoirs; reserve vertical pumps for deeper reservoirs. A common problem occurs when a powerful, vertically-oriented direct drive pump operates in shallow water. When water levels drop the pump will continue to push water well after the top of the pump is above water level. All the electronics live in the top of the pump, and when they overheat, it’s the beginning of the end, even with internal thermal switches that shut the pump down as it overheats. Underground, unmonitored, the pump will cool, the switch resets, and the cycle starts all over again. After a certain, very finite number of cycles both the switch and the pump will burn out. In general, while most direct drives are vertical, most Asynchronous Pumps are horizontal, so as soon as water levels drop to the level of the top of the pump they start sucking air, signaling a problem before they get a chance to overheat, and they are arguably less susceptible to low water damage, though any submersible pump for water features needs to be fully submerged. Asynchronous pumps are also very efficient and available up to around 8000 GPH; the use of multiple Asynch pumps can provide as much water as a big direct drive at a lower electrical cost. Visit the College of Pumps for more detailed information!
- Finally, use check valves to keep debris out of pumps. The tubing coming out of the pump offers direct access to the impeller inside the volute. Without a check valve, any pebble or debris at the top of the falls that gets sucked down the pipe when the power goes off will end up right where you don’t want it, inside the volute, ready to snap an impeller vane when the power goes back on. Check valves are cheap insurance to keep anything from going where it doesn’t belong.
