Thursday, February 23, 2012
Decrease Flow, Decrease Energy, Increase Circulation And Still Be Green
A pool is an item that can increase a person’s health, family time and enhance a backyard environment. But when the expense of maintaining the pool is beyond affordable after the initial expense, the dream can turn into a nightmare. While researching ways to make our pools safer from suction entrapment our industry found that slower flow is better for pool circulation and our pocketbooks. Having a “green pool” has new meaning.
Many people invest in a pool as a life-long dream. They work hard and save their money in hopes of having a backyard vacation and family area. Pools have become affordable for many and not just the very rich. However they do require energy to provide filtration, circulation and disinfection. Energy costs have increased since 1999 in the Southeast by 45.7% (U.S. Energy Information Administration). These rising energy costs and the imperative need to reduce our energy consumption has local governments issuing demands for energy reduction in all areas of building code. We are also looking to reduce our household budget demands during this economic downturn.
The swimming pool industry with the technical advancement of energy efficient pumps has been able to decrease the cost of running a pool by 90% or more. This can mean pennies a day. In the eighties the advancement of Dual Speed pumps gave us the ability to decrease costs by 75% over single speed pumps that are run the same amount of time per day. In the late nineties multi speed and variable speed pumps increased the savings even more. This is a significant reduction in energy. With more competitive production of these energy saving pumps and increase in energy costs the cost to the homeowners of the initial investment usually pays for the upgrade in months.
We use hydraulic calculations to know the resistance of the pool system, figure the turnover rate needed to properly maintain clarity and disinfection and size a pump to fit the swimming pool needs. One size fits all is no longer the educated way to purchase pool equipment.
A pump motor works on different rpm or revolutions per minute to turn the impellor which forces the water to flow. Swimming pool single speed motors use 3450 rpm. Dual speed motors drop to 1750 rpm and Variable speed can reduce to averages of 1350 to 1000 rpm. We are reducing the flow of the water and reducing the energy needed. It was found during technical trials in reducing flow of water for entrapment prevention (APSP/ANSI 7 2006) that we were using less energy as well as reducing velocity.
To move water slower in addition to reducing size and speed of a pump we can also look to our pool system and reduce the resistance to flow allowing for less energy to move the water. We can deliver more water through larger plumbing and reducing the amount of elbows and high resistance fittings such as multi port valves. This slower flow of water reduces the velocity and resistance of the water flow, reduces energy costs, but also is quieter, extends the life of the equipment, filters to smaller particles and better distribution of chemicals in the pool. We can run the pumps longer increasing the pool circulation and decrease the amount of chemicals needed.
When the speed is reduced from 3450 rpm to 1750 rpm (reduced by ½) we will get approximately ½ the amount of flow, and also have ¼ the amount of resistance (Total Dynamic Head in feet) which gives us 1/8 the electrical consumption. This is called the Affinity Law (Steve Barnes Pentair Power Point Presentation Florida Pool Show 2011). If we double the run time to compensate for longer turnover, we get ¼ the amount of energy savings. This equates to approximately 2.6 KW used for 16 hours of run time. With a single speed pump this would be approximately 8.1 KW!
When we apply the same principle to reducing speed even lower we can go as low as 1.9 KW to 1.4 KW for lower rpm. This is a substantial reduction in energy load. At the lowest amount we are only using 1.4KW to filter on a 24 hour basis.
With energy savings possible as shown above, it is within our reach to have a luxury item and be energy efficient. Spending a little more in initial cost is better than not being able to have a pool at all. If we have a product that consumes large amounts of energy it could possibly be legislated out of existence. A swimming pool being green is usually not a good idea but where energy costs are concerned it is the wave of the future.
Friday, February 17, 2012
An Old Swimming Pool Kid.: Pool& Spa Safety Act Falls Short of Safety
...: Pool & Spa Safety Act Falls Short of Safety In 2002 young Virginia Graeme Baker, granddaughter of Secretary of State James Baker...
...: Pool & Spa Safety Act Falls Short of Safety In 2002 young Virginia Graeme Baker, granddaughter of Secretary of State James Baker...
Pool & Spa Safety Act Falls Short of Safety
In 2002 young Virginia Graeme Baker, granddaughter of Secretary of State James Baker was held underwater by suction in a spa and drowned. In NC at a homeowner’s association pool another young girl was eviscerated by a suction line back in 1993 but was making news currently with her attorney John Edwards. Nancy Baker and Safe Kids Worldwide worked tirelessly to get Congress to enact laws for pool and spa safety. Representative Debbie Wasserman of Florida got the bill signed by President Bush known as the Pool and Spa Safety Act 2007. There was no doubt that even one accident is too many and a change needed to be made. Our industry was to learn so much more about hydraulics and entrapment. This newfound knowledge has caused many professionals to have issues and wonder why common sense and proven scientific studies have been ignored.
First the Consumer Protection Safety Commission studied from February 1985 to August 2002 how entrapment events occurred and how many resulted in death. We learned that of the recorded hair and limb entrapment events that 54% resulted in death. Body entrapment events accounted for 17% of deaths and of the 5 evisceration events that no death occurred. Most of these occurred in residential pools and not commercial. However the pool safety act was not retroactive to existing residential pools, only commercial pools. Many homeowners were led to believe that it was not important to them. Unfortunately residential pool owners have not seen the statistics nor has there been an aggressive campaign to educate them.
With technical research the adoption of dual main drains became required if main drains were being installed. No main drains were allowed as part of the ANSI /APSP 7 standard that was adopted by the Pool and Safety act also. The use of dual main drains was to slow the velocity down through the pipe so if one was covered and three feet away from each other so they both could not be blocked, that a strong enough suction would not occur to hold a body down or eviscerate. What Ms. Wasserman really did was double the chances for entrapment by limb and hair which had the highest percentage of deaths and injury of all types of entrapment. By doubling the occurrence of a missing or broken drain cover the new law succeeded to double our chances of death. This seems even more obnoxious as main drains are not needed at all for good circulation, cleaning or draining of any pool.
However we did learn that older drain covers are suspect to UV damage and now carry a date on them to be replaced. Design of main drain covers have been designed to hopefully mitigate mechanical and hair entrapment. It is very hard to see a main drain cover in the bottom of a deep pool or with any water movement.
We also have learned that if a cover is missing or broken regardless of flow that entrapment can occur. Human error cannot be legislated away.
The Pool and Spa Safety Act again failed in regards to suction entrapment. The allowance of a suction vacuum release system (SVRS) was heavily lobbied by the manufacturer of the device. This piece of equipment when in proper working order will shut off a pump within 3 seconds of low water flow and release the suction. However, even at the now required lower maximum velocity of water through the pipe at 3 feet per second for a single main drain the math shows that if blocked, nine feet of something could be sucked up the pipe within three seconds. That is still not acceptable and does not prevent evisceration. What is also not acceptable is the "water hammer"effect that could prevent the SVRS from cutting off power to the pump.
Much of the technical research done to prove the technical merits of ANSI/ APSP 7 standard has also created a better understanding of hydraulics which has led to energy efficiency and made our industry very aware of what we didn’t know. It has also increased awareness with code officials. The safety act was enforced before any training was available to the code officials or the public. Many pools were not opened due to costly repairs or not inspected properly many times. Few states have aligned their required codes which have put them in direct conflict with the federal act.
The most important change in legislation was not made as this bill was rushed through Congress before all the scientific studies could be concluded and expressed. Media attention on swimming pool safety was still high. It is now our responsibility to be sure the pools we maintain, install, or our family and friends swim in is safe. The only safe pool from entrapment has no main drain. It’s just that simple.
Tuesday, February 14, 2012
Total Dynamic Head and Why It’$ Important
Total Dynamic Head is the resistance that your pool water has to overcome to circulate and move within the pool hydraulic system. The flow of the water (hydraulics) is dependent on how easily it can move through the pipes, equipment, and pool fittings.
In our pool system we have a suction side and a return or pressure side. We can take gauge readings to determine what each is on our pool. But to calculate the entire system we must convert the suction and return readings to a common unit of measurement. We use the measurement of “feet of head” for this purpose. The pumps we use have charts supplied to us that show the “pump curve” or what flow the pump is capable of producing given a certain “feet of head” or “total dynamic head in feet” or with the resistance and friction loss.
We measure the suction side friction loss of our system in inches of mercury (Hg). We measure our return side in pressure per square inch (psi). To find common value for our measurements we look at the air pressure that surrounds us. When they have a common value of measurement we can add them together to get a total.
If we take pressure gauge readings 10 feet into a tank of water we will find 4.33 psi (pounds per square inch) is the pressure of the atmosphere pushing down on water. So using math we can determine that for every 1psi there is 2.31 feet of head (10 divided by 4.33 =2.31). When we take a pressure reading on a pool system we multiply that number by 2.31 to give us a measurement in feet of head.
Vacuum pressure is calculated in inches of mercury. At sea level there is 14.7 pounds per square inch pressing down on us by the atmosphere. If we use a vacuum pump you will see that the atmosphere pushing down on mercury will push it up into a tube 30 inches and no higher. If we do the same with a vacuum pump and water in a closed tube it will rise 33.9 feet and no higher. Therefore if we divide the water (which is in feet) by the mercury reading of 30 inches we conclude that we have 1.13 in feet of head. We use the 1.13 feet of head multiplied by the vacuum reading in inches to have a measurement in feet of head.
Now that we have our vacuum and suction readings in feet of head we can add them together to determine the Total Dynamic Head of the system or the total resistance we must overcome.
So, why is this important? This is important because we can determine how much water flow we have if we know what pump we are using. We can determine if we are getting the turnovers we need to keep our water clean and disinfected. We know if we have enough flow of water so that our equipment will work properly. We can also determine if we are producing more flow than what we need. If we are producing more flow than our system will allow than we have more resistance in our system and a higher total dynamic head than what is required.
The lower total dynamic head we have the less our pump and motor need to work. The less our pump and motor need to overcome the resistance the less energy will be required. The less energy that is required the less we pay for energy.
Many states have a new Energy Code that will require calculations to show the minimum pump size needed for your pool system. The days of thinking that the bigger the better are now gone. Energy efficiency is rewarded on some states with rebates on certain qualified equipment. Wattage per gallon is especially helpful to customers who want to have a pool that is cost efficient after installation.
Monday, February 6, 2012
Do You Know How Many Gallons Are In Your Recipe?
The above is a question I find myself asking customers in our store many times a day. When they answer that they do not know, I find these questions running through my mind:
1.) How do you know how much chemicals to add to your pool?
2.) How do you know how many hours a day to run your pool pump?
3.) Do you know if you are spending more than you should on energy and chemicals?
Likewise, the reason I am asking them in the first place how many gallons (or the size of their pool) is because they are asking me the following:
1.) Why is my motor running hot?
2.) I need to replace my pump what size do I need?
3.) I want better flow (they mean pressure usually which should not be confused with flow), can I increase the size of my pump?
4.) I want a new filter but don’t need to replace my pump. What size and type can I get?
5.) How much chlorine or other chemical should I add to my pool?
Everything we do on a swimming pool or spa is dependent on calculations. The entire design of the pool starts with calculations to properly size the circulation system or heart of the pool. This determines how many returns, suction inlets, lights, size of pipe, how much pipe and so on.
The equipment of your pool is the center of activity for your pool circulation. To get the water into your pool and back to the equipment in a manner that will keep your pool healthy is based on hydraulics. We determine the gallons in the pool, determine what our turnover rate should be (how many times the water is filtered in a day), the flow rate in gallons per minute and then calculate the resistance to be able to determine the proper pump size and match it to the filter type in order to achieve this.
Heaters, chlorine generators, and other equipment will not work correctly if the flow rate is less than the minimum required or over the maximum allowed.
Next we use the pool gallons and dosage directions to calculate chemical dosages so that we do not over dose or under dose the pool with chemicals. This will require calculations from the testing of the water and the amount needed to raise or to lower to adjust to accepted levels of given parameters.
So many times we find in our service department that someone has purchased equipment that they put on a pool will not function simply because someone did not do the math to find the flow rate required. Likewise adding chemicals without calculating how much is needed can be harmful and a waste of money if the results are not reached as expected.
Knowing your pool size and doing the calculations is like baking a cake with a recipe. If you don’t have a recipe and are just guessing you never know if the cake will be edible or maybe it will be edible but just look really bad.
Saturday, February 4, 2012
Many heros will be coming home soon. Many of our heros gave a part of themselves for our freedom but it also took away some of their personal freedom to move about freely. We all know how therapeutic water therapy can be for the disabled, the elderly and anyone with impaired movement.
The American Disabilities Act (ADA) has imposed rules regarding barrier removal for the disabled in regards to swimming pools specifically for primary and secondary access. There are five acceptable means of access. This rule is interpreted by each state in addition to the Justice Department. A state may have clauses in their building code which may be stricter than that of the Federal Department of Justice. This is true in North Carolina so what may be read online regarding fees or memberships to use pools in determining exclusions may not be correct on a state level.For pools over 300 linear feet, two means of access must be provided with at least one required primary access type. For smaller pools it is required to have one primary type access.
The two primary means of access would include mechanical lift chairs and also sloped entries to pools including ramps.
A mechanical lift chair can be permanently installed or be portable. It should be able to have controls so the person using the lift can use as well as someone outside the seat area. Various models are available with arm rests, foot support and portable batteries. Again check with your state code as some states will not allow a portable model.
The sloped entry can be built in or be a removable type ramp. Sloped entry is recommended if there are a large number of ambulatory users. The slope access must be thirty six inches wide (48 inches in NC, so check with your state building code) and slope twelve inches for every one foot in depth (1:12). For every thirty feet in length there must be a landing of level area of sixty inches long. Handrails and an aquatic mobile chair are required with slope or ramp entries.
The three secondary means of access consist of transfer walls, transfer systems and accessible pool stairs. The two primary means of access also qualify as secondary means of access.
A transfer wall is a wall where someone can transfer themselves from a wheelchair onto a wall and then ease themselves into the pool. There is a grab bar the width of the pool wall to help in transfer. A transfer system is similar to a wall where the person transfers from a wheel chair to the top of the device and then down the device into the pool water. A grab bar must be used on this system.
Accessible stairs offer support and rails for balance to enter the pool from a standing position and have rails.
The United States Access Board has provided a complete and very useful summary at:
The Association of Pool and Spa Professionals provides some Q&A facts, and updated Q&A linked by the highlighted words or available at www.apsp.org
The Dept. of Justice has provided an ADA 2010 Update on Accessibility as well.
As this is a complaint driven compliance issue, please be sure to check with your insurance company and counsel for the best policy and action to take. New construction must be compliant, and all existing pools must be compliant or have a plan in place by March 12, 2012. For further information please contact the Department of Justice at http://www.ada.gov/.