Energy Efficient Pumps in review
Many people ask me whether they should get an energy saving pump. Here is my take on why you should or shouldn't get an energy saving pump.
The energy efficient pump
An energy efficient pump is like any other pool pump except that it can vary the speed of the pump motor to reduce power consumption when it isn't needed and increase when it is required. This way you don't waste electricity on a high flow rate that isn't really necessary. If you don't need a lot of wayer circulating but need to run the pool for longer hours then an energy saving pump will help you save.
When is high speed necessary and when is a decrease ok?
Suction Cleaners such as a Kreepy Krauly Marathon, VTX7, or a Zodiac G2 automatically clean the walls and floors of your pool by utilising the suction power of your pump. These can often run on lower flow rates than a regular pool pump produces but sometimes a low flow rate can prevent them from working properly or stop them working all together. When considering a variable speed pump it is important to consider whether your cleaner can work effectively with the decreased flow.
These days, most pool owners have salt water chlorinators installed on their pools, at least here in Brisbane. Chlorinators require salt water to flow through an electrode to produce chlorine. That doesn't require a lot of water flow, just enough to keep the electrode fully immersed in water and keep the chlorine flowing back to the pool. What it does require is a minimum run time. In order to produce enough chlorine to sanitise your pool you will need to run your filtration a set number of hours each day, which is determined by your pool size and the chlorine output of your chlorinator. You can work this out by dividing your daily chlorine requirement by the hourly chlorine output of your chlorinator. For example a 50,000L pool will require about 200g (100% pure) chlorine each day. If the chlorinator produces 25g/hr you divide 200 by 25 to get 8, the number of hours required per day.
Automatic Dosing Systems
In general I recommend running your pump long enough to circulate the complete volume of your pool through your filter an absolute minimum of once a day. For a 50,000L pool with an Astral CTX280 pump (Flow rate 280LPM) that means a minimum of 3 hours running time. Of course that is a minimum and you should run it longer if you have a lot of leaves or other debris, the water temperature is above 24C, or you get a lot of freshwater added. Other factors such as heavy use can also increase the need for filtration. Filters don't need a high flow rate to effectively catch dirt and contaminants from the water and sand/media filters actually capture more with low flow rates because smaller particles are not forced through the filter media back into the pool. However, a higher flow rate is required for backwashing.
Chlorinator & Filter Combination
You may have surmised from above that often there is a mismatch between the filtration and chlorinator running time requirements. If you have a 25g/hr chlorinator and a 280LPM pump running you may only need to run your pump for 3 hours to sufficiently filter the pool water, but you will need to run it an additional 5 hours in order to reach the minimum run time for the chlorinator. This is where a variable speed pump comes in handy. Of course, you could get a larger chlorinator and I often recommend that for pool owners who have temperamental suction cleaners. However, it's usually better to run your system for more hours on a low flow setting as it keeps a steady flow of chlorine flowing into the pool for a longer period each day.
It's probably quite obvious that water features require a minimum flow rate. What that is will depend on the type and style of water feature. Waterfalls, for example, require a high flow rate of around 200-300LPM. You may be okay with leaving your water feature off most of the time and just running it for special occasions, in which case a variable speed pump will be fine. Whatever water feature you have it is important to consider the implications of a lower flow rate and evaluate whether that is ok for you.
In the end your pool and existing equipment will determine whether a variable speed pump is worthwhile for your pool. If there is a large difference between your chlorinator and filtration run-time requirements it could save you a lot of money on electricity. If you have a suction cleaner I would recommend a variable speed pump with adjustable settings like the Viron XT or H2Flo VSP pumps. These allow you to adjust the flow rate with precision so that your suction cleaner can still work effectively, while you wind back the flow rate as much as you can to save on power.