Pool Cert Flash 3. Filtration

Question 1

How does a Conventional Pressure Sand Filter (CPS) work and what is it’s flow rate limit?

Answer 1

Filters through several layers of various sized gravel and a layer of fine grained sand. Can operate at a flow rate no more than 3 gpm for each square foot of effective filter surface area.

Question 2

How do you know that a CPS filter requires backflushing?

Answer 2

When the pressure difference between the influent and effluent gauges reaches 6-8 psi.

Question 3

What is the process of backwashing and what is it for?

Answer 3

Reversing the flow of water through the filter and draining to waste. Removes mud ball formations, calcification of sand, and accumulation of organic matter trapped in the filter and discharges it to waste.

Question 4

What is the minimum backwash rate for sand filters?

Answer 4

15gpm/sq. ft.

Question 5

How do you back wash a CPS filter?

Answer 5

1. Turn off the pump and close valves both from the filter to pool and from pump to filter. 2. In multiple filter systems, adjust other valves so water can only be pumped through one filter tank. 3. Turn off pump and slowly open backwash valve. When water is clear, filter is clean. 4. Close both effluent and influent valves slowly so sand can settle evenly. 5. Repeat for each tank.

Question 6

What is a High Rate Sand Filter (HRS) and its use and limitations?

Answer 6

Smaller than CPS and uses only sand. Capable of filtration rates up to 20 gpm/sq. ft.

Question 7

How do you backwash an HRS Filter?

Answer 7

Perform when the difference b/n influent and effluent gauges reaches 10 to 15 psi. Same process as CPS Backwash. Backwash rate must be 15 gpm/sq. ft. For all closed filters, air must be released regularly.

Question 8

What is a Diatomaceous Earth Filter, it’s types?

Answer 8

Use finely crushed diatoms (tiny aquatic plant fossils) for filter media. Pressure and Vacuum Types.

Question 9

What characteristics differentiate Pressure (DE) Filters and it’s maximum filtration rate?

Answer 9

Use a pump ahead of filter to push water through the system. Maximum filtration rate is 1.5 gpm/sq. ft., except when continuous feeding (slurry fee) of DE is employed, then 2 gpm/sq. ft.

Question 10

What characteristics differentiate Vacuum (DE) Filters and it’s maximum filtration rate?

Answer 10

Use a pump after the filter to pull water through the system. Maximum filtration rate is 1.5 gpm/sq. ft., except when continuous feeding (slurry fee) of DE is employed, then 2 gpm/sq. ft.

Question 11

How do you know when Pressure and Vacuum (DE) filters need to be cleaned?

Answer 11

Pressure: pressure differential is 25 to 30 psi. Vacuum: 12 to 16 inches of Hg.

Question 12

How do you backwash DE filters (4 ways)?

Answer 12

1. Backwashing. 2. Air-bump-assist backwashing (momentary reversing surge of water casued by air trapped under pressure in system. 3. Spray washing (hose down filter surface). 4. Agitation (physically cleaning elements)

Question 13

What must you do before cleaning DE filters?

Answer 13

1. Turn pump off to release pressure holding DE material to elements. 2. Close valves to and from pool basin. 3. Open valve leading from filter to waste drain. 4. Wash out all DE material and Pre-coat.

Question 14

The filter removes _______ matter from the pool water.

Answer 14

Solid

Question 15

Name two different types of Diatomaceous Earth (DE) filters.

Answer 15

Pressure and Vacuum

Question 16

The rate of water flow through the filter is called?

Answer 16

Filtration Rate

Question 17

How is filtration rate determined?

Answer 17

Filtration Rate (gpm/sq. ft.) = Flow Rate (gpm) / Area of Filter (sq. ft.)

Question 18

The process of cleaning the filter by reversing the flow of water through the filter and draining to waste is called?

Answer 18

Backwashing

Question 19

The State of Illinois requires a 6” ______ be provided between the backwash pipe and the waste pipe?

Answer 19

Air gap

Question 20

A high rate sand filter should be backwashed when the difference between the influent and effluent pressure gauges reaches what level of psi?

Answer 20

10 to 15psi

Question 21

Tiny aquatic plant fossils are used as the filter media in what type of filters?

Answer 21

Diatomaceous Earth (DE)

Question 22

The maximum filtration rate for both vacuum and pressure (DE) filters is ____ gpm/sq. ft. except when continuous feeding of (DE) is employed, in which case the maximum filtration rate is _____ gpm/sq. ft.

Answer 22

1.5 gpm/sq. ft., 2.0gpm/sq. ft.

Question 23

(DE) filters must be _____ prior to operation. How is this done?

Answer 23

Pre-coated by isolating the filter from the pool and allowing the water to circulate from the filter to the pump and back to the filter. Once isolated, fill the filter tank or pre-coat pot with clean water and start the recirculation pump. Add 1.5 oz. of diatomite per sq. foot of filter surface area to the water. The diatomite will adhere evenly to filter surface. Flow should be directed to recycle through the filter or discharge to waste to avoid DE entering pool.

Question 24

Pressure (DE) filters should be cleaned when the pressure differential between the influent and effluent gauges is between___psi and ___psi.

Answer 24

25psi and 30psi

Question 25

Vacuum (DE) filters should be cleaned when the pressure differential between influent and effluent gauges is between ____ inches of Hg and _____ inches of Hg.

Answer 25

12 and 16 inches of Hg

Question 26

The State of Illinois requires high rate sand filters to be backwashed at a rate of 15 gpm/sq.ft, T or F?

Answer 26

T

Question 27

The State of Illinois requires all filters to be certified to comply with NSF Standard 50, T or F?

Answer 27

T