Pool Types

Question 1

What is a green pool?

Answer 1

Disinfectant-free. Water is purified by passing it over an open-air shallow filter bed that is planted with aquatic vegetation. Sand filters and UV disinfection may be incorporated.

Question 2

Pool Types?

Answer 2

Concrete, Liner, One piece, Above ground.

Question 3

What are the different concrete pool methods?

Answer 3

Sprayed concrete, temporary shuttering and permanent shuttering.

Question 4

How are liner pools made?

Answer 4

Excavating a hole, fitting a frame or shell and finishing with a high quality flexible PVC membrane (Liner). The shell can be made out of materials such as concrete, steel, aluminium, fibreglass or plastic panels. Takes about 4 weeks install. Life expectancy of 10-12 years.

Question 5

How are one piece swimming pools made?

Answer 5

Prefabricated Glass Reinforced Plastic (GRP). 95% of construction occurs in the factory. All necessary equipment can be fitted in the warehouse. The pool is craned into a pre-prepared excavation with a crushed gravel base. The gap between the pool and the soil surround is filled with gravel. It usually takes 5 days to install.

Question 6

What are the two common filter types?

Answer 6

Sand filter- Can be made of steel, thermo-plastic or fibreglass. Thermo-plastic and fibreglass are non-corrosive. Cartridge filter- force the water through a man-made filtration material.

Question 7

How are sand filters cleaned?

Answer 7

Backwashing. The pump is switched off and the position of a rotary or multiport valve is altered. Turning the pump back on thereby reverses the water flow. This expands and agitates the sand bed and the water carries away dirt particles. May only be needed about once a week in the peak system.

Question 8

How are cartridge filters cleaned?

Answer 8

Switch off the pump, remove the cartridge and soak the element in acidic degreasing cleaning agents. Wash it down before allowing to dry and replace.

Question 9

What are the finishing options for concrete pools?

Answer 9

The shell is coated with sand and cement wall plaster (render) and a floor plaster (screed). In some cases an additive can be mixed into these to make the pool watertight.
Finishing options include: mosaic tiles, tiles, natural stone, plaster finishes, painting and painting.

Question 10

How long can liners generally last?

Answer 10

8-10 years.

Question 11

What are the different type of pool covers?

Answer 11

Sheet covers, heat retention covers,PVC slatted covers, solar blankets,reel systems, winter covers.

Question 12

What are the different ways a pool can be heated?

Answer 12

Heat pumps, Gas and oil boilers, Direct resistance electric heating, solar panels, indoor pool heating.

Question 13

What are the different methods of shuttering a concrete pool?

Answer 13

Temporary- shuttering of steel or timber is removed once the poured concrete has set. Suitable for larger commercial contracts.
Permanent- Shuttering in the form of two skins of concrete blocks are often used for domestic installations.

Question 14

What are the different ways to spray a concrete pool?

Answer 14

Gunite- Dry mixed aggregate and cement are pumped to the spray nozzle where water is added.
Shotcrete- wet concrete is pre-mixed before being fed to the spray head.

Question 15

What is the difference between single phase and three phase?

Answer 15

Three phase has a larger power supply. It is more compact and less costly than a single phase.

Question 16

What are the steps of the pool circulation system?

Answer 16

The skimmer takes water in with suction produced by the pump. The main drain is another outlet for the water to reach the pump. The water then passes through the filter to the heater. Chemicals are then dosed into the water before returning to the pool via returns.

Question 17

Why is it essential to keep the water level consistent with the height of the skimmers?

Answer 17

It prevents air from being sucked into the skimmer. If air gets into the plumbing system, it can cause a loss in pressure and reduce the function of the circulation system.

Question 18

What is the rate that pool operators should replace pool water?

Answer 18

30 litres pet bather.

Question 19

Under what conditions do pumps operate best?

Answer 19

Under flooded suction conditions and be sited near the balance tank. If the plant room must be at a pool surround level, a pump pit will give flooded suction conditions.

Question 20

What temperature should a pool hall be?

Answer 20

No more than 1 degree above that of the water.

Question 21

Can multiple pools at different temperatures be operated by a single heat exchanger?

Answer 21

It may be possible using mixing valves and associated equipment to serve different pools at different temperatures. It is recommended that a separate heat exchanger with controls is provided for each separate pool water area- unless the pools share one filtration and circulation system.

Question 22

What are the problems with higher pool temperatures?

Answer 22

1.Microorganisms multiply faster (up to twice as fast for a 10 degree rise) Filters are increasingly likely to become colonised. 2. Bathers get hotter limiting serious swimming and increasing sweat/grease in the water. 3. Energy costs are higher. 4. Air temperatures rise too, making surrounding atmosphere uncomfortable. 5. Dissolves gases become less soluble, so more bad smells and potentially harmful gases.

Question 23

What are the recommended maximum pool water temperatures?

Answer 23

Competitive swimming- 28
Recreational- 29
Leisure- 30
Childrens teaching- 31
Babies, disabled- 32
Hydrotherapy- 35
Spa pools- 40

Question 24

What is the guideline ventilation rate?

Answer 24

10 litres per second per metre squared of total pool hall. This normally results in 6 air changes per hour but may need to be increased to 8 or 10 for extensive water features. A minimum of 12 litres of fresh air per second should be ventilated for each occupant of the pool hall.

Question 25

What is the maximum daily load rule of thumb?

Answer 25

20-50% of instantaneous bathing load x12.

Question 26

What is circulation rate and how do you calculate it?

Answer 26

The flow of water m3/hr to and from the pool through all the pipework and treatment system. Instantaneous bathing load x 1.7 OR water volume x turnover period.

Question 27

How do you calculate the turnover period?

Answer 27

Water volume / Circulation rate

Question 28

What are the suggested turnover periods for different types of pools?

Answer 28

Competitions 50m: 3-4 hours
Public up to 25m: 2.5-3 hours
Diving: 4-8 hours
Domestic: 4-8 hours
Hydrotherapy: 0.5-1.5 hours
Bubble: 5-20min
Leisure up to 0.5m: 10-45min
Leisure 1-1.5m: 1-2 hours
Leisure over 1.5m: 2-2.5hours
Domestic spas: 15min
Commercial spas: 6min
Learner pools: 0.5-1.5 hours
Waterslide splash pools: 0.5-1hours
Interactive water features: 20 mins

Question 29

What systems are there for removing surface water?

Answer 29

Deck level- The water in the pool is at the same level of the pool surround. Water is displaced over the edge through a grid cover into a transfer channel round the perimeter.
Overflow (scum)- Sills round the sides of the pool allow surface water entering them to flow through to connecting pipework.
Skimmers- Short, self-adjusting weirs installed at intervals around the sides of the pool. Efficiency is dependant on how many used.

Question 30

What do balance tank volumes need to accommodate for?

Answer 30

80 litres of water per bather for displacement, plus allowances for water loss during filter backwashing and for starting up the circulation system. As a rough guide balance tanks should have a volume of 10-20% of the hourly circulation rate. Most are as deep as the pool or slightly deeper.

Question 31

What should the total water calculation be based on for a balance tank?

Answer 31

The maximum water level being that of the base of the transfer channel. The minimum level being the least possible for the pumps to operate without drawing air. An allowance for filter backwashing. An allowance for bather displacement.

Question 32

How can a balance tank improve skimmer/scum systems?

Answer 32

The water level can be maintained at a pre-set, constant depth. The surface water removed can be more accurately controlled. Fresh make-up water can be introduced via the balance tank and automatically controlled. Filters can be backwashed without dropping the pool water level.

Question 33

How do you calculate the free open area of outlets?

Answer 33

Circulation of grille (m3/h) / 0.5x3600

Question 34

How do you calculate the size of the outlets to achieve a water velocity that doesn’t exceed 0.5m/s?

Answer 34

Total SA of grille= free open area(m2) / % outlet which is free open area

Question 35

What is the maximum velocity for inlet water?

Answer 35

Doesn’t generally exceed 1.5-2 m/s. As low as 0.5m/s in shallow/sensitive areas.

Question 36

When are VSD pumps suitable for use?

Answer 36

Assessment should look at treatment plant bather load capacity and pool tank bather load capacity. Only if there is a surplus in the treatment plant capacity at certain times should a VSD be considered. If a treatment plant is already under-sized or under-capacity, applying a VSD would only make it worse.

Question 37

How can you ensure that the pumps operate as efficiently as possible and with a maximised lifespan?

Answer 37

The distance between pumps and outlets/balance tanks should be minimised to reduce the overall friction loss on the suction side of the pump. If they cannot be close, the suction pipework size may need to be increased to reduce friction and thus ensure acceptably low pressure drop.