How to find a leak in a pool
Water loss from a pool normally varies between 3 mm and 6 mm per day due to evaporation, but greater loss indicates a leakage problem. It is possible that at certain point of time your outdoor concrete swimming pool starts leaking. Pool leaks can result from defects in the pool concrete shell or any of the plumbing associated with recirculation, filtration and spa systems.
The first and most obvious indicator that your pool has a leak is the loss of water and the lowering of the water level. To be sure that you really have a problem in your pool, a couple of simple test have to be done in order to determine the reason for the water loss.
Reasons for water loss in the outdoor pools
Generally, there are three reasons for water loss in the outdoor pools:
- Natural evaporation and splash-out. Depending on the climatic characteristics of the region you live in, your pool may lose certain amount of water due to natural evaporation. The people who are using the pool can also splash out quite a big amount of water.
- Leaks in the plumbing lines. Leaky valves, leaky seals, leaky pump (lid or body) or a broken pipe could result into major water losses and have to be repaired as soon as possible.
- Concrete shell leaks. Even the smallest cracks in the tiles and plaster may cause a solid water loss. Very often leaks come from the areas where the skimmers, the lights, the return jets and the other fittings are installed into the pool’s shell.
HOW TO DETERMINE THE REASON OF THE WATER LOSS IN MY POOL?
1. Water loss through evaporation from pool water surface
Evaporation is the changing of water from a liquid state to a gas. It is usually used to indicate a state change below the boiling point of water. To determine if the water loss comes from evaporation fill a transparent container or a jar with water and place on the first pool step or fix it somehow floating in the water ( THE BUCKET TEST). It is important that the water level in the pool is the same as the water level in the container and the pool is not used during the test. If there is a difference in the water levels after a couple of days (for example – the pool level is lower than the container level) this means that your pool has a leak.
Swimming Pool Water Loss Calculator
2. A leak in the swimming pool plumbing system
The basic configuration of a swimming pool plumbing and filtration system is simple. Water is pulled through the skimmers and main drain in the swimming pool by the pool pump. Then the water travels through the pipes back to the filter room where it passes through the pump and is then pushed through the filter, and is returned back into the pool through the return lines. The plumbing systems are a constant source for water loss for a lot of different reasons ranging from pipes material, installation quality, age, configuration and soil conditions. Before you begin to tear apart your plumbing system you need to locate the leak in the plumbing system first.
Swimming pool with Sand filter filtration 
The procedure used to monitor and log the water lever over given period (usually over a week) of time is called a “Hydrostatic diagnostic test”.
The test will return one of these options:
1/ The pool is losing the same amount of water regardless if the pump is on or off:
=> broken pipe, leak around skimmers, lights, drain, multiple leak locations
2/ The pool is leaking more when the pump is on, but water loss is experienced in both conditions:
=> loose fitting or crack in return line, multiple return line leaks
3/ The pool is leaking more when the pump is off, but water loss is experienced in both conditions:
=> loose fitting or crack in suction line, multiple leak locations
4/ The pool is leaking when the pump is on, and not leaking when the plumbing system is off:
=> crack in the return part of the plumbing
5/ The pool is leaking when the pump is off, and not leaking when the plumbing system is on:
=> crack in the suction part of the plumbing
Should the monitoring results indicate a difference in rate of water loss when the plumbing system is running and when it is shut off, this can be a strong indicator for a problem existing in your plumbing system.
A simple inspection of the area around the pool could be very helpful to detect a leak from the plumbing. To determine if the leak comes from the plumbing you have to investigate the ground around the pool, the filter and pump area and all the pipes coming from and going into the pool. If you see a wet or damp spot, follow the line to find the trouble-maker.
Both ways – the conclusions from the hydrostatic test and the pool inspection would help you to discover by yourselve the reason for the water loss but in any case it is recommended to call a professional to deal with the problem.
3. A leak in the pool’s shell
When the water loss is the same regardless if the plumbing system is running or not, then you probably have a leak in the structure of the pool itself, and not in the plumbing system.
Underwater leaks in the shell and the fittings can be identified with the help of special dye – the so called “Leak Detection Dye Test“. First of all you have to turn off the pump and wait until the water is calm. By adding some dye in the water near suspicious cracks, the skimmers, the return lines, the lights and all other underwater fittings piercing the pool’s shell you will be able to determine where the problem is. If there is a leak, the dye will be sucked into it. The leaks from the shell should not be underestimated or ignored, because they may lead to even bigger structural damages, not to mention the high water bill and the excessive usage of chemicals.
No matter if the leak is in the plumbing or in the shell, prompt measures have to be taken to eliminate the problem and to avoid further damages. As an experienced builder of concrete swimming pools, we are familiar with all most probable leakage places and can help identifying and repairing the leak in your pool.
How to repair leaks in your swimming pool
Because of significant loss of water a client contacted our company to undertake the repair of his outdoor swimming pool. The pool was losing water and the leakage was damaging the pool’s neighboring area.
It was ascertained that the concrete shell was leaking through cracks in the tiles and through the underwater fittings. The unprofessional execution of the construction works, especially in the skimmers and return lines zones was ascertained when the skimmers’ bodies and the return inlets were removed.
1. Skimmers and inlets
When we drilled around the skimmers and the inlets we found there big holes filled with brick pieces instead of waterproof concrete and plaster.
The areas were cleaned carefully from brick pieces and wooden shattering remains and after that filled with hydraulic cement in order to prevent any further leakage from these particular zones.
When the cement filling dried out new tilling in the areas was professionally installed, leaving no visual trace of the repair.
2. Shell cracks
When building a concrete pool it is essential to execute the body as a monolithic structure free from work joints in order to avoid movement or cracking within the pool shell, water loss and subsequent damages.
In our case, the upper part of the pool had been concreted separately from the rest of the pool’s body and thus forming a joint. In the course of time, really bad cracks had appeared in the pool’s tiling. The water was leaking through the holes and was destroying the area around the pool and damaging the stone ground tiling. These cracks were also very dangerous for the concrete pool shell itself. If not cured these cracks would continue to erode the concrete and the forces involved would keep on pulling the cracks apart. It was not possible just to glue or plaster them over, to fill them with some epoxy and silicone products, or other pool repair putties. More serious measures had to be taken.
3. Chiseling along the crack line
In order to make the walls as monolithic as possible we had to chisel around the joint and clear the damaged concrete. The openings were then filled with hydraulic cement that would connect the two separate parts of the wall into one monolithic structure free from cracks, joints and other leaking zones.
After the cement was dry the places were plastered with hydro insulation and the tiling was renewed. After the repair, the walls were looking as good as new.
4. The plumbing
This particular pool didn’t had any leaks from the plumbing itself but from the places where the pipes were installed. There were large openings where the pipes were going into and out of the pool’ s walls filled again with brick pieces and mortar. Through these holes the pool was leaking in the ground and destroying the neighboring area. We assume, two separate building companies had executed the concrete works and the pipework without any coordination between each other and the results are abvious. And again the brick pieces were carefully removed and the gaps around the pipes were filled with hydraulic cement which is a special cement mixture that expands as it dries and is mainly used to fill the void areas in foundations around water pipes, foundation form holes, electric wire sleeves and others of this kind.
5. Repairs of the damaged yard tiles outside the pool
Because of the numerous leaks from the pool, the tiled sun area around the swimming pool were damaged also. The leaking water had drained into the soil and the ground had sunk unevenly. Some tiles were loose or broken. The client had assigned our company to repair the problematic areas and to install new tiles.
The tiles were completely removed, a new stell reinforcement installed and concreted. When the concrete dried, the new tiles were installed to the complete satisfaction of the client.
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