The 7 most common sprinkler tank defects
Sprinkler tanks hold the fire water for the sprinkler system – if they fail, fire protection is at risk. From the waterline zone to the liner, a range of defects can impair their function. In this article we show which typical damage occurs in in-ground tanks and steel tanks and how underwater drones record it – without draining the tank. This makes it possible to detect damage early and plan repairs before they become expensive.
Inspecting sprinkler tanks without draining – underwater drones at work
In the event of a fire, every sprinkler tank must work properly. Its task is clear: to provide fire water immediately and reliably.
Experience shows, however, that typical defects occur more often as tanks age, even with regular maintenance. The inspection of sprinkler tanks is described in rules such as VdS CEA 4001 and the FM Global standards; our footage supports the inspection by the expert assessor.
From the waterline zone to the liner, the weak points are many and can jeopardise the function of the entire system. Underwater drones record the condition of the tank while the water stays in it. In this article we present the seven most common defects and show how inspection by underwater drone detects them and in many cases saves you from draining the tank.
Christian Engelke
1. Defects in the waterline zone
The waterline zone lies around the waterline of a sprinkler tank, where the water level changes through consumption, refilling and evaporation and where condensate forms. The alternation between wet and dry conditions puts the coating and the material surface under stress, which over the years can lead to cracks or spalling.
In the long term, this creeping damage can lead to corrosion, particularly in free-standing steel tanks, and weaken the protective coating. Regular inspections with underwater drones make it possible to monitor the condition of the waterline zone closely without having to drain the tank. Early intervention helps to avoid greater damage and considerably extends the service life of the tank.
2. Pipe defects caused by sediment abrasion
Sediment settling on the tank floor can be carried into the pipework by the water flow during weekly pump tests and cause abrasion there. Pump systems and supply lines are particularly affected; the recurring load leads to increased wear and ultimately to cracks or leaks.
The causes often lie in sediment deposits formed by corrosion or dirt particles in the water, and in the mechanical stress on the pipes from the constant flow of water during the tests. If sediment is not removed over long periods, the problem gets worse.
The consequences: abrasion by sediment can cause considerable damage to the pipework and impair the functioning of the system.
Prevention: underwater drones make it possible to detect sediment deposits early, so that cleaning of the tanks can be arranged in good time, before the weekly pump tests cause serious damage.
3. Algae growth and increased corrosion from algal metabolism
In free-standing tanks, algae growth can become a problem, especially when light and nutrients are present in the water. The metabolism of the algae releases chemical compounds that accelerate corrosion of the tank's metal components.
Typical causes are light entering the tank, which encourages algae growth, nutrient input into the water, and the metabolic products of the algae, which increase the risk of corrosion.
The consequences: corrosion caused by algae can considerably weaken the metal structures, particularly pipes and anti-vortex plates.
Prevention: regular inspections with underwater drones reveal algae growth early, so that the affected areas can be cleaned before major damage from biogenic corrosion occurs.
4. Defective pipe supports due to corrosion
Pipe supports and fixings that are not made of stainless material are particularly susceptible to corrosion. Inferior materials that are not suitable for permanent contact with water often lead to serious defects.
Typical causes are the use of inferior or non-stainless materials, constant contact with water and a damp environment, and missing or inadequate corrosion protection.
The consequences: corroded pipe supports can lead to unstable pipework, which jeopardises the entire system. In some cases, pipes can even break and fall into the vessel, damaging the vessel itself.
Prevention: underwater drones can be used to inspect the pipe supports in a targeted way. Corroded or defective parts are detected early and can be replaced before major damage to the system or the vessel occurs.
5. Cracks in the liner of free-standing steel tanks
Free-standing sprinkler tanks are often fitted with a liner that holds the water in the tank. Cracks or damage in this liner cause the tank to leak, so that not enough water is available.
Typical causes are mechanical impact during maintenance, ageing of the liner leading to embrittlement, and stresses caused by water movement in the tank.
The consequences: cracks in the liner make the tank leak, which impairs water availability and means the tank can no longer fulfil its function.
Prevention: underwater drones examine the liner throughout the tank and reveal defects, so that countermeasures can be taken in good time, before larger problems arise.
6. Severe corrosion on pipes and anti-vortex plates
The pipes and anti-vortex plates inside the tank are particularly susceptible to corrosion, as they are in constant contact with water. The regular pump tests also repeatedly introduce oxygen into the tank, which can accelerate corrosion further. If the corrosion protection is inadequate or damaged, serious damage can occur within a short time.
Typical causes are constant contact with water and the oxygen additionally introduced by the pump tests, damaged or worn corrosion protection, and increased chloride content or other chemical contamination in the water.
The consequences: corrosion considerably weakens the structural integrity of the pipes and anti-vortex plates, which can impair their function in the sprinkler system.
Prevention: regular inspections with underwater drones show the corrosion condition of these components, so that repairs or replacement can be planned in good time, before larger problems arise.
7. Foreign objects in the tank
Foreign objects, such as parts left from maintenance work or other contaminants, can cause considerable malfunctions in the tank. They can clog pipework or block pump systems. Rusted-off pipe clamps, pipe sections or pieces of sheet metal are particularly problematic, as they can cause further damage if they go undetected.
Typical causes are carelessness during maintenance or cleaning, foreign objects entering through leaking or open maintenance hatches, and deposits of rust or other materials.
The consequences: foreign objects can block pumps and pipes and so considerably impair the functioning of the sprinkler system.
Prevention: underwater drones show foreign objects before they affect the installation. We can recover smaller objects such as rusted-off parts with the gripper arm of our underwater drone; whether this is possible in an individual case is clarified in advance.
Tank inspected, fire protection kept ready
A fire suppression system is only as good as its fire water supply – and sprinkler tanks play a central role in it. Regular checks are essential so that the system works in an emergency. Without an underwater drone, this requires divers or draining the tank.
Inspection by underwater drone solves this problem: it records the condition of the tank comprehensively while the tank stays full and the fire water supply remains available. Corrosion, cracks or deposits are detected early and recorded in the inspection report with their location in the tank (wall, height, fitting). This increases safety and provides a sound basis for planning necessary repairs. You can learn more about our approach under Inspection of sprinkler tanks and water tanks.