“Which filter choice is right for me and my pool?” is a common question often asked of me to which there is really no definitive answer. The 3 leading choices available for pools today are DE (or Diatomaceous Earth), Cartridge, and Sand filters. There is no “perfect” filter choice for any pool - all have their strong points and all also have drawbacks. It is my hope that this general discussion of filter types listing advantages and disadvantages will help you make the right choice for your individual situation.
The operative terms in pool filtration are “EFFICIENCY” and “CAPACITY”. Efficiency refers to how small a particle of dirt, measured in microns, a filter is capable of trapping and is the most important term in determining water clarity. To help put this into perspective, particles start to become visible to the naked eye in the 35 to 100 micron range. Examples of particles in this range include some pollens (30-50 microns), human hair (50-70 microns or so in diameter), beach sand (around 100 microns in size). It is important that any pool filter be more efficient than this, as most bacteria, single cell algae and the like are much smaller than 35 microns. The more efficient a filter is, the clearer it can make your pool water. Capacity refers to how much dirt afilter can hold before it needs service, backwashing or cleaning. Capacity is typically measured in “square feet of surface area” for pool filters. The greater the capacity of a filter, the longer it can run between cleanings. The filter pressure gauge is used with all filters to determine when it is time to clean the filter. It is always important to know the “clean” pressure of your filter system. As the filter catches dirt, it becomes harder for water to flow through the filter and the pressure on the gauge begins to rise.
DE or Diatomaceous Earth filters have long been touted as the “best” type of filter for a swimming pool. Diatomaceous Earth is a fine white powder, somewhat similar to sand but much smaller in size, that is used in all DE filters to catch the dirt from your pool water. They are “best” in terms of efficiency by far compared to the other choices of filtration available for your pool. Regardless of manufacturer or design, all DE filters have an efficiency rating of 3-5 microns which is truly microscopic in size. A typical DE pool filter has some sort of fabric covered hollow elements inside. The fabric is woven tightly enough so that water can pass through to the inside, but Diatomaceous Earth cannot. DE is fed through the pool skimmer while the pump is running and flows into the filter, coating the fabric element evenly with a layer of DE. Water flows through the DE, through the fabric, and is collected clean inside the elements and returned to the swimming pool. Diatomaceous earth filters for residential pools are cleaned by backwashing. Backwashing involves moving a valve or valves to reverse flow through the filter. Water is sent backwards to the inside of the elements, flushing out the dirt the filter has caught and also the used DE coating, and sending them out of the system to waste. Once cleaned, valves are changed to restore flow in the proper direction, and a new coating of DE is fed through the skimmer into the filter, “re-charging” it with the proper amount of DE. While DE filters are truly the best in terms of efficiency, they can be a little unforgiving at times to operate. Simply put, nothing much gets through a properly functioning DE filter and they can clog quite rapidly under dirty water conditions. As such, they require more frequent monitoring and regular backwashing and recharging with DE to keep them running at peak efficiency. A Pentair FNS PLUS DE filter is the right choice for anyone who wants the clearest possible water and is prepared to spend some regular time on simple filter maintenance.
Advantages of owning a Diatomaceous Earth (DE) Filter:
* Most efficient of all filter types available for pools (can catch the smallest particles of debris down to 3 microns). This is true of all DE filters regardless of style due to the fact that it is the DE that catches the dirt from the pool.
* Relatively large surface area compared to some other types of filters.
* Modern style of grid filters we sell are easy to take apart, service and clean.
*Modern style of grid filters we sell come with a multiport 6- position control valve for service flexibility.
Disadvantages of owning a Diatomaceous Earth (DE) Filter:
*Need to learn proper backwashing technique and backwash regularly to keep filter running at peak efficiency.
*Because filter is so efficient, it can be unforgiving if you are not keeping up with the other aspects of pool care, particularly water sanitization.
*Need to buy, use, store DE and dispose of spent DE after backwashing.
Cartridge filters have been available for many years but are making a resurgence in popularity due to favorable changes in engineering and design. A typical swimming pool cartridge filter uses a set of pleated cartridges to catch the dirt from your pool water. While not as efficient as a DE filter, cartridge filters do pretty well and catch particles in the 8-30 micron range. This small sacrifice in efficiency is made up for in greatly increased capacity. Cartridge filters typically have a capacity about 9 times larger than a DE filter with a similar tank size. This translates into a tremendous savings in time spent on pool maintenance. With all other factors being equal, a cartridge filter is cleaned once for about every 9 times a DE filter would require maintenance. While not particularly recommended, it is possible for a properly sized cartridge filter to run an entire swimming season without much attention or cleaning. Cartridge filters can also save water and chemicals in your pool, as there is no backwashing out of any pool water to clean a cartridge filter. When the filter gets dirty (as indicated by pressure rise on the gauge), the cartridges are removed from the filter, hosed off with a garden hose, and replaced in the tank again when clean. The old adage “time is money” applies to cartridge filtration, however. Since we are relying on the large capacity of this style of filter to save us time on regular maintenance, there can be a higher cost of ownership of a cartridge filter. The elements typically have a useful life span of 2-5 years, depending on conditions and care, before they need to be replaced. A Pentair CLEAN AND CLEAR PLUS cartridge filter is the best choice for someone who doesn’t mind spending a little more money to save a lot of time on in season pool maintenance.
Advantages of owning a Cartridge Filter:
*Great time save! Super large surface area (capacity) relative to filter tank size gives longest filter cycle before filter requires cleaning. Can be sized to run the whole season with minimal cleaning or attention.
*Still reasonably efficient (6-8 micron capability)
*Great water savings. Filter requires no backwashing so water and chemicals stay in the pool.
*Modern style of cartridge filter we sell are easy to take apart and clean.
Disadvantages of owning a Cartridge Filter:
*When it is time to clean the filter, it must be physically disassembled and the cartridges rinsed off with a hose.
*Higher cost of ownership than other filter types. Because we are using this filter to save our time, there is a cost in replacing the filter elements every 3-5 years on average. (time vs. money)
Sand filters have been around as long as swimming pools have. With a typical modern sand filter, pool water is forced through a bed of sand, which catches the dirt, and then returned to the swimming pool. Sand filters are cleaned by backwashing which reverses flow through the sand bed and flushes captured dirt out of the sand and to waste. The sand stays in the filter and is reused over and over again. Sand filters score lowest in both efficiency (25-80 microns particle size) and capacity (the capacity of a sand filter is typically the surface area of the top of the sand bed), but are still in use today because they are simple and low cost to understand and operate. Because of their relatively small capacity compared to other choices of filter, sand filters require frequent backwashing and waste the most water and pool chemicals in the process. Sand filters can help keep a clean pool clean and presentable, but due to their low efficiency and small capacity, can rather quickly show their limitations under extreme circumstances. For those who prefer the time tested simplicity of sand, Pentair TRITON II sand filters are among the finest available.
Now that you know the basics, if you still have any questions regarding the proper choice and recommended size of filter for your pool, please give me a call or email. It is our job to make sure your pool is as easy and trouble free as possible to care for.
Here is some information to help you in your thinking and planning process.
There are so many choices on the market today that selecting the one that is right for you can be a bit confusing. What type of heater is best for your pool? What size heater do you need? Often, we only hear the "good stuff" from manufacturers and sales info, but are left to wonder about or find out the hard way some of the "not so good stuff". Typically in our area, we see GAS FIRED POOL HEATERS, POOL HEAT PUMPS, AND SOLAR POOL HEATING SYSTEMS. Each has their own advantages and disadvantages that we try to address briefly in this blog post.
The first thing you need to know is that it CAN be quite expensive to heat any swimming pool, particularly if you are counting on your heater to extend the season by a number of weeks early in the spring and later into the fall. It is usually more practical to use a heater to enhance your normal swimming season by giving you more swimmable days. How many times have you gone out on a cloudy day in the summer and wished the pool was just 5 degrees or so warmer so it would be more comfortable to get in? This is the true value of a pool heater in our Maryland climate - owning a pool heater can give you the maximum number of swimmable days in our short swimming season and used in this way can be relatively inexpensive to run. How inexpensive or expensive it is to heat your pool depends on quite a few factors that include size of the pool in surface area, capacity of the pool in gallons, environmental conditions at your particular pool location (windy, woodsy, sunny, etc), temperature differential between air and pool (how cold is it outside vs. how warm do we want the pool?), and whether we are using the pool heater for maintenance heating (heating the pool and then maintaining a constant temperature throughout the season) or demand heating (heating the pool intermittently only as needed and when desired). Most manufacturer heater sizing charts are based on “average” environmental conditions and usually include one chart for maintenance heating based on pool surface area and one chart for demand heating based on pool capacity in gallons. It is important to remember that all pools (and spas and any body of water) loose 90% or better of their heat through evaporative cooling through the surface area of the pool. Utilizing a SOLAR BLANKET with any pool heater cuts evaporative heat loss to a minimum and is the single best thing you can do to minimize energy costs with any type of heating system. Solar blankets typically are cut to fit and float on the top of the pool water.
SIZE MATTERS!! Regarding HEATER SIZING, you should always check the manufacturer charts to make sure you are never buying a heater that is simply too small to effectively heat your pool. If you select a heater that is marginal or too small for your size pool, chances are you are just throwing you money away as it can never heat your pool the way you want. BIGGER IS USUALLY BETTER!! Gas heaters and electric Heat Pumps are usually rated in bTU sizes. By way of example, assume we have two identical pools right next to each other in exactly the same environmental conditions and want to heat both pools from 60 degrees to 85 degrees. Pool #1 is heated by a gas fired 250,000 bTU heater and pool #2 is heated by a gas fired 400,000 bTU heater. In a “textbook” situation, by the time both both pools reach 85 degrees both will have used EXACTLY THE SAME AMOUNT OF GAS to do the job. Pool #2 with the larger size heater will have simply done the job in about half the amount of time. In practical (not “textbook”) application, since pools loose a great amount of heat through the surface area and this loss is constant based on time, the larger capacity heater can actually use LESS GAS over time because there is less heat loss during the shorter heat up time!
GAS FIRED POOL HEATERS, while more expensive in terms of energy cost than other alternatives, are usually the best overall choice for heating any pool in our service area. They seem to give the best balanced combination of comparatively low initial cost, quick heat up time, fuel consumption and cost, and ongoing service and maintenance. Blue Waters has technicians that are capable of repairing just about any problem you may have with your gas fired pool heater. They are available for either propane (LPG) and natural gas use, depending on what is available in your area and also available with either electronic ignition or standing pilot (millivolt) versions. While the millivolt heaters cost a little less up front, electronic ignition is usually more trouble-free over your years of ownership. If you have a pool and spa combo and/or you want to be sure, no matter what the conditions that your pool is heated when you need it, then beyond a shadow of a doubt an electronic ignition gas fired heater is the best choice for you. For the reasons above, it is usually best to choose the largest size heater available for your pool. Just remember to check with your local gas supplier to make sure they can supply the gas to feed your heater.
SWIMMING POOL HEAT PUMPS definitely win in the category of efficiency of fuel cost over gas fired pool heaters. When you read this in manufacturer information, it is not a lie. Be careful to look at the big picture, though. Heat pumps by nature heat whatever they are heating (pool or house) very slowly - usually by only a fraction of a degree per hour. For this reason, they are better thought of for “maintenance” heating rather than “demand” heating. The colder it is outside, the less heat is available to “pump” into your pool and the heat pump becomes less effective. At air temperatures too much below 50 degrees, most swimming pool heat pumps become unable to add any significant heat to your pool. They are also more costly to purchase up front (often twice the cost of a gas fired pool heater) and because they utilize a mix of technologies (they are similar to an air conditioner working in reverse to add heat to a pool) it is often difficult to know who to call to solve your heat pump service problem. Control and water chemistry and flow issues can usually be handled by Blue Waters Inc.,your pool service company, but the refrigeration aspects usually require an HVAC technician. You are a good canditate for a heat pump if you simply want the lowest energy cost to run your heater, religiously use a solar blanket or have a relatively small pool in terms of surface area, are never in any particular hurry to get the pool up to temperature, and don’t really ever have the need to extend your season too far in either direction and/or for any reason cannot get any kind of gas supply on your property. If you are considering a heat pump for your pool, remember again that BIGGER IS USUALLY BETTER. Blue Waters will be happy to recommend a quality heat pump that can best meet your needs.
WHY NOT BOTH? Adding one of each to your pool gives you the best of all worlds. The powerful, fast heating gas fired heater can be used to handle the extreme circumstances of overcoming cold air temperatures, extended seasons or needed quick “demand” heating and the much more econimical heat pump can be used to take over the “maintenance” heating to keep the pool warm at the lowest energy cost.
SOLAR HEATING SYSTEMS can be quite tempting with their promise of “free” energy to heat your pool. Usually composed of large, dark colored panels that your pool water flows through to be heated by the sun, solar heating systems need a rather large area that is exposed to constant sunshine to do their job. The larger the surface area of the solar panels, the more heat they are capable of adding to the pool. They are typically mounted on the sunny side of the roof of your home and require re-piping of the pool to divert water through the solar panels to be heated when the sun is shining. While this is a great concept, remember that solar heaters only work when it is warm and sunny outside - typically the times you need to heat your pool the least. If it is cloudy or cool outside, a solar system has the potential to work in reverse, acting like a large “radiator” that can increase the surface area heat loss of the pool if pool water is flowing through it during a non-desirable period such as a cool day or night. If you have a suitable location to mount a solar heating system, they are best used to simply keep the cost of energy used by gas heaters or heat pumps lower, but can be rather disappointing in our climate as a stand-alone heating system.