Tiled Swimming Pools and Leaks
Why tiled pools
leak
Introduction
Sometims we are asked
if we can build a tiled pool in our operational area in SW France
and our answer is always "Yes - but it would be very costly
and we do not build them"
The question posed in
the title of this weblog can be answered with the simple statement
"Most tiled pools leak because of faulty design and installation
procedures"
Let's take look at what
is required in ensuring that a tiled pool does not leak and then
compare the technology with PVC liner pool technology.
The design and construction
of tiled pools
Tiles can only be placed
on walls and floors that are structurally rigid and that do not
flex under water pressure, ground pressure or temperature change.
If flexing occurs the tiles will come off. The tiles themselves
are not water-proof and so the structure itself has to provide the
water-proofing.
Across the globe such
structures are often formed with Gunite that involves projecting
concrete pneumatically at high speed onto a natural ground surface
or onto a formed surface using shuttering. Reinforcement consisting
of steel wires or rods is put in place before so that the gunite
surrounds them and becomes "reinforced concrete". The
method of construction allows both curved and flat shapes to be
formed and is in common usage in Australia and the US. It does require
good ground conditions because it is impractical to build thick
sections using this technology.
In SW France the ground
conditions are often poor at pool sites and so conventional reinforced
concrete construction would be required. This involves the construction
of a heavily reinforced slab base (250 to 300 mm thick) and walls
(180 to 200 mm thick).
In either case the structure
must be designed by an experienced fully qualified civil / structural
engineer who will take all the ground conditions, pool size, pool
depth etc into account.
The most important construction
issue relates to the joint between the heavy ground slab and the
walls. The slab obviously has to be cast first. The shutters for
the walls are then erected and the walls concrete poured a day or
so later. This results in a joint that is virtually impossible to
water-proof in a 200 mm thick wall.
Hence the water-proofing
is provided by a water-proof membrane that is applied to the surface
of the very expensive pool structure. The quality of the membrane
and the leakiness of the pool relies entirely on the materials used,
the mix proportions, the mixing and the skill and integrity of the
plasterer.
Other ceramic tiled pool construction issues
There are various other
construction issues that need to be taken into account in the design
and installation of a ceramic tiled pool and these include:
1. The concrete base
slab and the walls will need to be cleaned by water blasting, shot
blasting, grit blasting etc to ensure that the render / screed sticks
on - these are all very dirty processes that take a lot of time
to undertake
2. The concrete base slab and the walls will need to be levelled
with render / screed to get the necessary flatness for tile installation
(< 3mm in 3m) - this may also need cleaning before the membrane
is applied
3. After levelling the waterproof membrane will need to be applied
- this will be a proprietary latex based product mixed with Portland
cement that will stop moisture penetration, moisture expansion,
chemical attack by chlorides and efflorescence. The membrane will
need to cure for 7 days at 20 + degrees C.
4. After curing the pool will need to be flood tested for leaks
- this will involve filling at a slow rate of 600 mm in 24 hours.
Fugitive dyes and a scuba diver will be required to locate any leaks
5. Mosaic tiles will need to be paper faced ceramics as back mounted
mosaics can come off the wall following saturation and pool water
chemical attack
6. Tiles must be impervious or vitreous to reduce the effects of
moisture expansion and to eliminate freeze / thaw problems
7. The tile mortar bed must be latex based to reduce chemical attack
and improve flexibility to withstand moisture expansion and shrinkage
or epoxy based (expensive and can be difficult to use)
8. The grout can be latex based or epoxy based - epoxies can discolour
under sunlight.
9. Movement joints must be provided in the tiling in strict accordance
with the grout manufacturer's installation instructions
10. The latex based beds and grouts will need to cure for 14 days
at 20 degees C (10 days for epoxies)
11. Pool to be filled at 600 mm per 24 hours to prevent excessive
water pressure, thermal and moisture differentials. Filling should
not proceed in direct hot sunlight or with very cold water
Through the wall
pool equipment and main drain
There is another major
potential problem with tiled pools that relates to the "through
the wall equipment" and the main drain. These items are made
in high quality plastic that is not suceptible to corrosion from
the chlorinated water in the pool. But whilst the plastic is excellent
from a corrosion point of view the concrete that is cast around
the plastic inserts like the skimmers and main drain etc tends to
shrink away from it and it is virtually impossible to stop leaks
occuring, particularly around the main drain where the water head
is highest.
In a liner pool mechanical
joints with high quality gaskets are installed - these virtually
never leak and if they do because of faulty installation - the joint
is easy to repair.
So It is no wonder that tiled pools take so long to build and are
so susceptible to leakage!!
Ceramic tiled pool operational issues
The control of pool water
chemistry is very important in ceramic tiled pools:
1. Chlorine uses and
depletes calcium and so calcium balance is essential to prevent
deterioration of cement based grouts and mortars
2. If the pH is too high mineral deposits will form on the tiles
and grout - they can form under the surface of the ceramic tiles
causing the surface to come off the tiles
3. If the pH is too low acidic etching of the grouts and mortars
can occur
4. If the calcium hardness is too low the pool water will etch calcium
from the grout and if it is too high calcium deposits can form on
any of the pool surfaces
5. At normal pH values iron and copper metals will come out of solution
and can then be deposited as stain on tiles, grout and pool fittings
Another common problem
is that the skimmers become loose in the concrete wall in which
they are built. This results in leakage that can only be cured with
putty that is unsightly and likely to be picked out by small fingers!
PVC liner pool technology
When everything is taken
into consideration it is difficult to understand why anyone would
want to take the risk of building a ceramic tiled pool - that is
why we do not build them!
PVC liner pools:
* Will not leak even
under quite large structural movements in the pool walls and floor
* Can be renewed comparatively cheaply (800 to 1000 euros) and easily
on a DIY basis
* Allow leaks to be easily located and repaired (this will be the
subject of a future weblog)
* Are virtually impervious to chemical attack (calcium deposition
can occur but PVC is much easier to clean than tiling and grout)
And last but not least
they look terrific!
Summary
PVC liner pools
cost half of what ceramic tiled pools cost and are superior in just
about every way. They are based on the latest material technology
and are environmentally friendly because of the reduced requirement
for energy intensive cement and steel products.
Ceramic tiled pools are based on 40 year old technology and rely
on modern chemical additives to work!
And if you do not believe me just click on this link
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at 15 Avenue de Lattre de Tassigny, 17500 Jonzac, France
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