by Victor K. de Fontenay
  PREPARING THE POOL AREA
4.0 PREPARING THE POOL AREA
- 4.1 Selecting the Area
- When you prepare to select the area in which the pool is to be constructed, you must conside the following points:
- Can the pool be seen from the Kitchen & or the Family room, irrespective of what fences or other safety devices you have around the pool, it should always be located where it can be seen by an adult whilst children are using it.
- Is the access to the pool convienent from the Family room or deck area or varendah, you don't want to be walking around the back of the house to the pool all the time. Also you don't want the children to have to trapse all through the house in their wet swimwear to go to the toilet or shower.
- Is the area one in which the pool will get the most sunshine & the lease leaves from overhanging trees.
- Will noise from the pool become offencive to the neighbours & cause problems in the future.
- Will the pool fit in aesthetically with the rest of the property.
- 4.2 Picking the Level Area Point
- If you have a sloping block of land, you will need to pick a point which will be the top level of the pool. This point could be at the deep end, centre or shallow end of the pool.
If you pick the deep end then you may find that a lot of the pool is below the natural ground level & you have to build retaining walls.
If you pick the shallow end than you may find that a lot of the pool is above the natural ground & you will have to do a lot of backfilling to make a level path or you may want to create a sloping walk way around the deep end of the pool.
Normally it is easier to pick the centre of the pool & this way you have approx half of the pool which may need a retaining wall to stop the garden running into the pool & the other half will have to be built up using the dirt dug from the other end. It is not easy at times to get an idea of how the pool will be looking untill the area in which it is to be constructed is leveled & then the pool marked out using flourecent paint on the level ground.
- 4.3 Checking for Utilities
Always contact the Water, Gas, Electricity, & Telephone companies prior to any digging to make sure that there are no utility pipes or cables in the area where you wish to build the pool.You may find there are utilities there and you will have to make the decision to either move the pool position or to move the utilities.
- 4.4 Allowing for Drainage
When you build the pool on a sloping block & even on a reasonably level block, you will need to make allowance for drainage of rain & splash water from around the pool area.You will need to be very careful to drain water from the high side of the pool, where you may have built a retaining wall or there may be a natural rock wall. You want to provide specfic drainage to remove water from these areas. Also make sure to allow for drainage in the area between the pool & the house, you dont want lawn or even concrete in that area to be continually wet.
- 4.5 Access for Removal of Spoil
Many time with building blocks gettting smaller & smaller, it is getting harder to have access to remove the soil dug from the pool hole. If you are in a tight situation then you may have to use a bobcat or very small excavator to dig the hole & you may need to use a conveyor belt system to transport the dirt to the street for loading on to a truck.
4.6 Reuse of Spoil
As I have said eariler, dont leave the dirt or soil or rock from the pool dig on site unless it is being used for fill. (See Photo) If you are using it for fill then try to carry out the fill & compaction at the same time as the dig so that you do not get mounds of dirt in the way of your work. Always place the fill dirt in 150mm layers & then compact, then another 150mm & then compact again until the desired level is reached. You may have to store store some fill for backfilling close to the pool wall later but any other fill should be placed at digging time.
5.0 CONSTRUCTION SEQUENCE
The following instructions are a brief outline & it is preferable if the user has some knowledge of building prior to starting on a project such as a swimming pool. These notes are provide to allow persons to have some knowledge of what a contractor or sub contractor should be doing while building a pool.
- 5.1 LAYOUT - POSITION
Considering the points in 1.4 above, the whole area in which the pool is to be built should be marked out so that you have a good idea of the total area you will be using.
Normally I do this with some cans of flurocent paint, Light blue for the basic shape of the pool, brown for the surround area, red for extended paving, & green for new pr moved garden beds. This can be easily seen for a distance when you stand back to get a distance perspective or stand inside & look out the window to see how the end result will look.
Once you are happy with the layout of the area then confirm the position of the pool & mark its outline (150mm outside the finished internal dimentions) for a normal concrete construction. This is the line which the digger will dig to.
Pick your datum point (see 2.1.2) & decide the relivance this has to the top level of the pool. As you will need to refer back to this point all through the construction.
Make it a point which will not get disturbed & which can be seen from any point in the pool construction area.
- 5.2 EXCAVATION
DO NOT LEAVE THE EARTH DUG FROM THE POOL ON SITE Unless there is more than adiquate room or only if there is a specific need for leveling the yard etc.
In most cases if you leave the earth in the yard, it will get in the way of the digger & it will make a mess as well as making it very hard to keep the worksite clean.
If the earth is used for fill on another part of the land, then in most cases it must be spread 150mm thick & then compacted & then another 150mm & then compaction, up to the required level. This should be done as soon as it is excavated.
If you dig a normal 9.5M x 4.5M pool, you can get upto 100 CubM of earth out of the hole.
Where possible use the biggest machine possible, a good large machine, especially an excavator can move the earth much more efficently than a small machine costing less per hour but more over all. If you use a large machine make sure that there are enough trucks to keep up with it. The machine is costing you money while it is sitting idle waiting for a truck to load.
Make sure to check of underground utilities prior to digging.
Make sure that you have identified the level that the top of the pool will finish at so that you can use this as a fixed point from which to check dig depths.
You will need a dumpy level or water level to be able to check the depth of the excavation at various points along the floor.
Where possible try to dig from the deepest point to the shallowest. it easier for the excavator operator.
Make sure that the markout for the shape of the pool is 150mm (6") outside the finished internal line of the pool. (Less if using Fibrecrete & more if the engineer asks for thicker walls)
Make sure that the excavator operator does not dig back past the lines as it will cost you more concrete to bring the internal wall face to its correct lines.
Beware of rock or underground water seepage below ground level, both could increase the cost of the excavation.
If you strike water seepage, it can cost you for dewatering for not only the dig time but possibly through out the construction or at least untill the concrete shell is complete.
Always try to have the excavator trim as close to the perfect line as possible as he can carry out a lot of work much quicker than it being done by hand. (see photo)
Remember that you need to dig the floor to a depth to allow for at least 75mm of gravel underdrain & 150mm of concrete floor.
You can let the walls come in slightly as they go down, about 50mm for each 1000mm in depth.
Remember the deepest point should be equal distance from the two side walls & the deepend wall.
The walls at the deepend should be straight down for 1500mm then curve into the deepest point see accompanying typical drawings. Wall Drawing
Dig out area for skimmer box & dig pit 450mm x 450mm x 450mm at the deepest point for the hydrostatic valve which is connected to the main drain. Dig a grouve in the floor & wall to run the pipe from the main drain to the skimmer box, normally 40mm PVC pressure pipe.
It will normally be necessary to excavate for a bond or ring beam around the top of the pool which is usually twice the thickness of the pool. Beam/Wall This may have to be done by hand.
- 5.3 FITTING INCORPORATED ITEMS.
- 5.3.1 SKIMMER BOX '(S),
Most pools will have one or more skimmer boxes for drawing the water from the surface of the pool. (normall allow one skimmer per 50SqM of pool surface area.
The skimmer box should be mounted so that the mouth faces the prevailing winds, the skimmer box does not have to be in the deep end of the pool but must work with the wind which is blowing leaves etc across the water surface.
The skimmer box should be mounted such that the centre of its mouth is 150mm below the top of the pool.
Make sure that the skimmer box is set level & upright.
Connect a pipe to the suction point on the skimmer box, this pipe will have to go back to the area where you have your pump & filter. (normaly 50mm PVC pressure pipe)
Connect a pipe to the drain connection on the skimmer box, this pipe goes to the main drain in the base of the pool. (this pipe is normally 40mm PVC pressure pipe.)
Make sure to seal the front & top of the skimmer box to prevent concrete or concrete slurry entering during concreting.
(Some pools have an overflow gutter or weir or level deck, these don't have a skimmer box, see here for information)
Make sure to seal the top of the main drain to stop concrete of concrete slurry getting in during concreting. The maindrain must be protected from entry of cementous compounds for the entire construction period.
- 5.3.2 MAIN DRAINS
The main drain is a unit which is set at the lowest point of the pool.
The main drain has a perforated pipe in its base which is set in the gravel in the pit at the deepest point of the pool. There is also a pipe which connects from the side of the main drain to the skimmer box.
Set the main drain level with the deepest point required in the pool.
Set the main drain level. (see photo)
The main drain normally includes a removable dress ring & grated lid which are not installed at the start, these are set in the final finish of the pool.
- 5.3.3 RETURNS
These are the pipes which allow the water to return to the pool from the pump & filter.
Preferably use the following formula
.660 kW Pump = one return
1.0kW Pump = Two returns
1.25kW Pump = Three returns
1.5kW Pump = Four returns.
The returns should be set at least 300mm below the surface of the pool water or 450mm below the top of the pool. Use 40mm Class 9 PVC Pressure pipe through the walls.
Set the returns such that they will drive the water in a circular motion to force floating debri on the surface to go towards the skimmer box.
If you have an extra deep pool, (more than 1.8M deep), then place one of your returns 750mm below the top in the deep area.
Use two elbows in the wall with each return to reduce the chance of leaking around the pipe.
If only one return is used then use one 40mm pipe to feed it, if two or more returns are used then use one 50mm pipe to feed them & using 50mm tees, branch off to each return.
Make sure to tape up or put caps on the ends of the returns so that concrete does not enter them.
You can set up the returns with a short section of pipe protruding out past the top edge form around the pool & connect on to them after the shell is finished or you can connect them together & run the main feed line back to the area where the pump & filter will be straight away.
- 5.3.4 LIGHT CONDUITS
Light conduits shoud be install so that they project into the pool 450mm below the level of the water or 600mm below the top of the pool.
Use orange 25mm conduit & terminate it 300mm out from the pool.
Seal the end of the conduits before concreting
- 5.3.5 OVERFLOW
If you live in a high rainfall area, then it is necessary to have an overflow line (normally 40mm PVC Pressure pipe) installed with the base of the pipe set 25mm above the centre line of the skimmer box mouth opening.
When you recieve heavy rains this will drain off excess water collected into the pool.
Seal the end of the pipe before concreting
- 5.3.6 MAKEUP LINE
If you wish to connect an automatic makeup line to the pool to allow it to automatically fill when necessary, the run this line in 25mm PVC pressure pipe to a point a safe distance from the pool.
This line should enter the pool at least 150mm below water level. & it MUST be set LEVEL back to where you install the level controller. (See notes provided by manufacturers with level controllers for more specific installation proceedures)
Seal the end of the pipe before concreting
5.4 FORMWORK - BASE - STEEL
- 5.4.1 FORMWORK
To provide an outline edge for the top of the pool & the bond or ring beam, a form must be set up to the shape of the pool.
This form can be timber of steel of fibreglass & is usually 200 to 300mm high. The top of the form is set perfectly level for finishing the concrete. (see photo)
The level of the top of the form, relitave to the finished top of the pool is dependent upon the thickness of the coping or deck being used. If it is a tile or aggrigate the top of the pool may only be 20mm below the finished level, if it is a brick or paving slab deck then it maybe 75mm below the finished level, if it is concrete with Kooldeck or similar then the for will be 100mm below the finished level.
If the pool is more out of the ground on one end or one side then the formwork on that side will be higher than on the other.
5.4.2 SUPPORT LAYER
Once you have the floor & walls of the excavation trimmed to your requirements, then your will need to spread 75mm min of 20mm gravel across the floor area to act as a drainage layer below the concrete. This gravel must be spread to meet the gravel surrounding the main drain at the deepest point.
The support layer must be covered by a membrane to stop the concrete getting into it & rendering it in effective. Many people use a layer of builders polythene but I find this to slippery to work on & prefer to use either Bitumen (tar) inpregnated paper or a thin bitumen membrane sheet.
5.4.3 STEEL
Once the formwork is in place, then the steel for reinforcing the concrete must be bent & put in place. (see photo)
Depending upon the pool design & the length, width & depth & the engineer, the pool will normally use either 10 or 12mm deformed bar at 200 to 300mm centers in both directions. Be sure to tie the steel at each cross over & flattern every tie wire so it does not stick up through the concrete.
The steel will be bent at the top out to the formwork & will usually carry an extra three bars around the top in the bond/ring beam on the horizontal .
Extra steel will be needed around the skimmer box & the main drain. (see photo)
The steel must be set in accordance with an engineers recommendations but would usually be set to have at least 60mm cover on the dirt face & 75mm cover on the water face. This can be achieved with the use of plastic bar chairs available in both sizes.
The steel is normally bent with a 300mm radius bend at the floor wall joint in the shallow end & up to 600mm radius in the deep end.
If you are doing a flat bottom pool. then reduce the steel floor wall joint radius to 150mm.
All of the steel in the pool must be connected to an earth strap along with any other metal objects (hand rails, ladders) in the pool. This earth strap must be connected back to the main house earth at the switch board.
5.5 CONCRETE,
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Concreting of swimming pools is normally carried out using a spray concrete. The special spray concrete mix is delivered in to a concrete pump which pumps the concrete to a nozzle which uses compressed air to blast the concrete on to the earth & build up a thick wall encompassing the steel. (see photo)
When spray concreting is being carried out, there is always the possibility of overspray.
It is necessary to cover any nearby garden, parths, house walls & windows etc so that the strong, cement rich concrete does not get on to these items.
The spraying of the concrete is always carried out by professional concrete sprayers.(see photo)
Once the concrete has been sprayed on & cut to the finished shape. (See Photo)
The concrete must be cured for a minimum of seven days.
This is usually carried out by wetting the surface every 3-4 hours with a garden hose.
This is ok but it is better to fully cover & tape in place a complete thin plastic cover hard against the concrete.
This must be taped at the joints to stop air entering & drying the concrete.
5.6 COPING - DECKING
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The coping or decking around the pool can be of many finishes & can vary from 300mm to many metres wide.
Normally most engineers design a pool with a bond/edge beam 300mm wide around the top & this is covered with a material of the same width in aggrigate, brick, stone or large quarry tile. This should be laid by a compertent trades person.
Most times there is a path or deck associated with the pool & this can either be at the same level as the coping or set lower than the coping, if you want to make the area around the pool look larger then set the decking at the same level as the coping.
The finish on the deck can be the same as the coping or can be of a different material.
If you are setting a deck associated with the pool & butting it up to the coping, there will be a expansion joint between the two lots of concrete. It is inadvisable to pave over the joint. The joint should be sealed with a joint sealer such as SIKAFLEX to stop water entering it.
To give a cleaner finish to the surround, you can finish the top on the pool shell 100mm below the finished level of the deck around & pour the concrete deck right over the beam of the pool creating a joint on the horizontal instead of the vertical.
This effect can be enhansed by incorporating bull nose edges etc. The form for this can be obtained from any KOOLDECK agent. You can use tile or paving or Kooldeck as a finish on the uninterupted deck area. http://www.mortex.com
5.7 INTERNAL FINISHES
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5.7.1 TILING , PART & FULL
There are a number of ways in which you can finish the interior of the pool shell & all of these systems have been discussed in sections previous to the construction section.
Following are some points specific to application of the finishes.
5.7.2 TILE BEAM
300mm deep plus Pebble or Marble plaster or liner.
When applying this type of finish, the top band of tiles must be laid first before the coping finish. The tiles must be laid on a screed which has been set with a plaster mix approx 15mm thick which is used to give a nice clean line to the top edge of the pool & makes up for any irregularities in the concrete shell.
The tiles must be laid with the joint nearest to the level 150mm below the top of the pool being perfectly level. This way the water looks level when it is at its correct level.
The tiles must be laid on a cement based adhesive to give long term adhesion.
When the tiles have been laid & grouted, then the pool coping should be set in place & it will be perfectly level as it relates to the tiles.
If you are then using pebble or marble plaster finish, this should be applied up to the bottom of the tile line.
5.7.3 MARBLE PLASTER (MARCITE) FINISH, It must be done in one go from start to finish without a stop. Marble Plaster finishes require the use of special plastic trowls to smooth the plaster but not burn it.
The dress ring component of the main drain will be installed into the plaster over the main drain hole during your application of plaster.
The plaster must be covered with water starting about 4-6 hours after it is finished to allow it to cure under water. It is necessary to make sure that the water you are using to fill a plaster pool is clean & free from iron or copper or manganese or any other chemical which could stain the new finish.
A plaster pool finish will need to be brushed daily from about the fourth day to the 30th day to remove any minerals or other sediment which may try to adhere to it.
The pH, Alkalinity & Calcium Hardness levels must be kept correct with a plaster pool other wise the water will damage the plaster & could even make it fall off long term.
The pH, Alkalinity & Calcium Hardness levels must be kept correct with a pebble pool other wise the water will damage the plaster & could even make it fall off long term.
5.7.4 FULLY TILED
A fully tiled pool starts by plastering the concrete pool shell with approx 15mm thickness of 3-1 plaster.
Next the top row of tiles are set in place & the subsequent layers down to & across the floor. Some tradespersons may want to finish the coping after they have done the first row of tiles, & before they do the rest of the tiles. I think this is a good idea as it means that it is easier to do the coping & if a little mess gets on the pool floor then it can be cleaned easily & does not damage anything.
Tiles of the same color & size through out can be used or you may wish to run a top border of a lighter or darker color and or you may want to high light the floor wall ares with a different color or style.
You have many choises of tiles but think of how you will like looking at the same tiles for the next 20 years before you make your decision.
5.7.5 FULLY PEBBLED
The fully pebbled pools ususlly have the coping done first and the tradesperson will try to get the top coping as level as possible but it may never be as level as if tiles were set first. Next the pebble will be laid through out as with the tile/pebble system & all the same precautions must be taken.
When applying a PEBBLE finish, extreme care must be taken to make sure that the cement residue which gets washed off the pebble does not wash down into the main drain.
The dress ring component of the main drain must be installed & sealed using the pebble mix.
5.7.6 FIBREGLASSED
Many pools have a layer of fibreglass laid over cement plaster which as been applied to the concrete shell.
The fibreglass is usually laid in four layers. It is usual to have to wait 28 days from when the plaster is finished until when the fibreglassing can be done to allow the plaster to cure & to release its moisture.
Once the fibreglass has been applied, it should last for many years.
Always make sure that the applicator uses vinylester resin for the fibreglassing.
5.8 EQUIPMENT INSTALLATION
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Once the pool shell is finished & before the surround concrete or decking is done, you will need to connect the pump suction pipe to the skimmer box or boxes & the filter return line to the return eyeballs.
LAYOUT:
Before you complete these lines, draw out on the ground the layout of your pump & filter & any accessories which will be located in the same area, eg salt chlorinator cell or gas heater or solar pump. So that you do not have pipes crossing over & looking untidy. Many times a pump will sit on the right or the left of the filter but with some filters it will only sit on the right or the left.
SUPPORT SLAB:
You should then bring your suction line, return line, & backwash lines up through the ground in the correct places & then form up & pour a concrete slab large enough for every thing to sit on easily. Also see ELECTRICAL CONNECTION below before proceeding.
Sit all the equipment on the slab & make sure that there is good alignment for the pipes between each piece of equipment.
VALVING:
If the equipment is set below water level, then you will need an ON/OFF valve on the suction line & a CHECK - NON RETURN valve on the return to pool line. These should be place d before & after all equipment.
It is preferable that the pump not be more than 500mm above water level unless a CHECK valve is used in the suction line below water level. (Be careful as these valves in this position tend to catch leaves etc).
PUMP:
The pump should be set so that you have easy access to the lint strainer on the front as it may need to be cleaned weekly.
FILTER:
Always sit the & filter so that you can easily access the backwash valve & also see the clear site glass on the backwash line if the filter has a site glass.. Also allow for future access for maintainance of the filter.
ACCESSORIES:
When installing a salt chlorinator cell in the return line, make sure to install it in accordance with the manufacturers directions otherwise you could have problems. Give careful thought as to how to comply with the recommendations & still have a neat installation with the least number of bends.
If you are installing a gas heater, then you must connect the heater such that it always has water in it. This is usually accomplished by the use of positive loops on the inlet & outlet & if the is above water then a check valve on the inlet to the heater can be an advantage.
You may also need to install a line (40mm) from the return line to the solar pump if you have a solar system for heating your pool. The other possible lines are:
Feed to the spa as a seperate return.
Pressure line for a pressure type pool cleaner
Feed to jets in a spa.
5.9 ELECTRICAL CONNECTIONS
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There are a number of connections which could need to be made at this point.
- Power to the pump & filter area.
For normal single pump allow 10amps
For pump & lights allow 15 amps
For pump & solar pump allow 20 amps
For pump & spa pump & blower allow 25 amps
- Set a post in to the equipment concrete slab on to which you can mount the control switches if you dont have a wall nearby.
- Bring the main conduit feed to the post or the wall for the power.
- Bring up the conduits for the lights if the transformers are to be mounted near the equipment.
- Make sure to connect the main earth to the earth straps which come from the pool steel & hand rails or any other metal object in the pool.
5.10 SURROUND WORK
Once all of the pipework & conduits and make up water etc are in place, then any surround concrete or paving can be laid in position.
Before actuall concreting or paving the area, make sure that there is adiquate drainage from the actual area & also from any uphill areas adjacent. This may require the installation of actual underground drainage or sub soil aggi drains to make sure the areal is left dry & not muddy after a rain.
The surround area can be of many different types of material but make sure that the material selected & used is compatible with the area It is always advisable to take some professional advise on the surround material for you area.
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