People don’t consider their water tank. Until it gets into trouble, that is. Then, one day, it is the most important thing in building. A leaking tank, contaminated water or a structural fault in the middle of the summer is the type of issue that seems like it shouldn’t happen, and does not.
Water tank maintenance is not difficult. It is consistent. This guide teaches you all the details of how to keep your tank in great working order, your water clean, and your tank as long as you can.
The Importance of Routine Water Tank Maintenance
One of the most neglected assets of a property, whether residential, commercial or industrial is a water tank. It is assumed to provide water supply, store water and deliver water. Until it doesn’t.
If water tanks are not maintained over time, dirt and sediment settle in the bottom of the tank, bacteria proliferate on the film that forms on the tank’s inner walls, and structural problems gradually become costly repairs. Always prevention is cheaper than crisis.
This is also serious from a health perspective. Legionnaire’s disease is a potentially deadly pneumonia caused by Legionella bacteria that grow in unused warm water tanks. CDC states that the major factors that influence the growth of Legionella are disinfectant residual, water age, temperature, biofilm, and sediment. Each of those factors is directly related to routine, proactive maintenance.
How long can a water tank last?
First, it is best to set expectations, before you start talking about water tank maintenance. The lifespan of the tank differs according to material and care.
Generally, concrete water tanks have a life of 20 to 30 years and in good condition can last for over 50 years. The life of polyethylene plastic tanks is also generally in the range of 10 to 20 years depending on quality tank, location and environmental conditions (25 to 30 years for quality UV stabilised tanks in sheltered conditions). S. Stainless steel tanks generally have a useful life of 20 years or more, especially if they are kept away from harsh conditions. Under favourable conditions, coated, well-maintained steel tanks can be expected to last up to 50 years.
The message is clear: the difference between minimum and maximum lifetimes is virtually all due to maintenance quality. Regular inspections and maintenance have gotten a concrete tank to 50 years. Failure at 15 years is almost certainly a failure.
Schedule regular inspections (at least once per year).
Health and safety guidance such as UK HSG274 Part 2 and ASHRAE Guideline 12-2000 suggests that hot or cold systems using elevated hold tanks should be inspected and cleaned on an annual basis to reduce the risk of bacteria developing within the system.
Inspection includes both internal and external. Externally inspect for damp spots, stains, surface cracks, and fittings, valves and pipe connections. Internally (after draining the tank) check for sediment at the bottom of the tank, biofilm on the walls and bottom, corrosion, mould or insect/vermin entry.
Never miss out the lid and access hatch. If the cover is not a proper fit, or if it is damaged, insects, air-borne debris and microorganisms can enter the tank. If the cover has not sealed properly, a clean looking tank may be very contaminated on the inside.
Bacteria samples should be taken from drinking water tanks every six months. For non-drinking water applications, test frequency will be based on your risk assessment and control plan.
2. Thoroughly clean the tank at least once a year.
Inspection is a way of discovering the condition. Cleaning addresses it. Annual cleaning is not always required by law, but annual inspection is; and inspection is always followed up by the need for cleaning.
The frequency is not as important as the process. Remove all the water from the tank completely, to clean the interior walls and bottom. Clean the base to remove sediment, using suitable tools. Clean the inside with a neutral, non-abrasive cleaning solution and a stiff brush or high-pressure wash with a non-abrasive solution that will not strip the inside of coatings. Allow solution to sit in the tank for a while before draining; after draining, rinse well and let the tank air dry before refilling.
Disinfection after tank cleaning (using a suitable chlorine solution at the right concentration) eliminates the remaining bacteria, and restores water safety for tanks providing drinking water. Then thoroughly rinse it out with clean water before it goes back to service, to remove excess chlorine.
Always remember: do not enter confined spaces unless trained, assessed and equipped for the job. Water tanks can be considered confined spaces, and entry into such a space without precautions results in a true accident each year.
3. Regulate water temperature and avoid bacterial growth.
This is the easiest maintenance tip to forget, and the science behind it is very straightforward. Legionella bacteria grow most actively in water temperatures between 25°C and 45°C. CDC advise to store cold water below 20°C and hot water above 60°C to maintain conditions outside the growth favour.
Cold water tanks placed in roof spaces without insulation, or in direct sunlight in warm climates, can become hot enough to actively promote the proliferation of bacteria. Cold water tanks should be well insulated to prevent the water within from becoming warm. Hot water tanks hold the water at the right safe temperature by means of insulation throughout the system.
Regularly check temperature at certain points around the house, near the outlets located farthest from the tank. When the hot water system is not providing the desired hot water at the farthest points, it is an indicator that the water system design or insulation should be investigated.
Check for Leaks, Cracks, and Structural Damage!
Leaks can cause serious health and economic problems if they are not resolved. A minor leak in a hairline crack allows moisture on the tank’s outside which fosters mould growth, structural deterioration, and water loss. If a leak occurs in a large tank in a region where water is a major cost, then it is an actual continuous expense.
In the case of concrete tanks, hairline cracks are not necessarily a cause for concern, although any cracks that leak or allow water to enter or exit should be addressed promptly. Water that is discolored or cloudy may mean that the water is breaking down or is starting to get contaminated. If the water pressure is low, it may be due to leakages in the walls of the tank and connected pipes.
In plastic tanks, check for surface crazing, structural deformation or brittleness, especially for tanks exposed to a lot of UV. Polyethylene will weaken with time when exposed to direct sunlight, developing cracks and eventually failing. Wherever possible, place plastic tanks in shaded areas or provide UV-protective tank covers.
Check all service fittings, inlet and outlet valves, pipe connections at each service. Close or re-seal loose joints before they can turn into leak points.
5. Manage Sediment Accumulation
Over time, sediments accumulate in all water tanks. It accumulates at the bottom when flow is low or none, and when it is established, it offers nutrients and surface area for bacterial growth, including that of Legionella. A positive relationship between opportunistic pathogens and nutrients in the sediment of water storage tanks has been reported in scientific literature.
Periodic flushing of the tank, not simply at the annual clean, helps to prevent sediment from settling. The ASHRAE and OSHA are both recommending that hot water storage tanks be drained annually to remove scale and sediment deposits, especially for hot water tanks. Sediment and scale affect efficiency of the heating system, cause the heating system to run harder, and lead to higher energy bills. That’s where flushing comes into its own.
In industrial and larger commercial tanks, the ‘rule of thumb’ when it comes to predictive maintenance is simple: if the tank is monitored regularly for sediment builds up, it will allow for early detection, and intervention takes place before the localised corrosion or deterioration of stored water quality.
Promptly repair, replace, and maintain valves, fittings and connected equipment
A water tank is not a standalone tank. It’s only as good as each of its inlet and outlet valves, float assembly, overflow pipe and filter through which they are connected. A leaking or broken float valve can cause water to continuously trickle over, resulting in loss of water and potential damage to the surrounding area by the dripping water. A clogged inlet filter cuts off supplies. Pressure is limited by a stuck outlet valve.
Flush twice a year all connected valves. Ensure that overflow pipes are not blocked and away from building. Check filter housings for sediment loading and change filter media as recommended by your filter supplier. If your tank is fitted with a thermostatic mixing valve, service the unit twice annually according to manufacturer’s recommendations; the valve is often the source of a tank’s thermal failure.
Record each service, each test and each corrective action. If there are no records, then it is impossible to recognise any trends to reoccurring risk, or to show compliance should an inspection authority ask for it. As a rule of thumb, records should be kept for at least 5 years.
7. Avoid UV, environmental damage and contamination entry
Think about how to fix the damage in advance of it happening to the tank as it happens from external attack, either actively or passively, is very easy to fix if you think about it in advance and difficult to fix when it has already occurred.
Plastic tanks will be worn down over time from the UV radiation, even those that are made with UV inhibitors. This is slower but not terminated. If tanks are not placed in direct prolonged sunshine, or covered with protective material, their service life is effectively increased. In coastal areas, corrosion due to exposure to salt air is the main external risk to metal tanks. Protective coatings require regular checks and maintenance prior to complete breakdown.
Maintain a clean, litter free area around the tank. Inspections are made more difficult and external materials introduced into the water tank at maintenance times are more likely when a tank room or installation area is contaminated.
You should contact a professional if you encounter any of these issues:
There are some maintenance activities that require trained and certified personnel, such as cleaning and disinfection, confined space entry, legionella risk assessment, and major structural repair. This isn’t a matter of playing it safe because of that. This is because poor quality water has direct health implications and cleaning chemicals can have their own hazards if used improperly.
Generally, replacement is more cost effective than repair if the cost of the repair is over 50% of the cost of a new installation. The cost of downtime and risk from a deteriorating tank far outweighs the cost of capital for more frequent repairs.
This is a Simple Maintenance Schedule Summary report.
Continuous monitoring of water colour, pressure, quality as per normal practice, twice-yearly valve and fitting service, 6 monthly temperature checks at sentinel points, 6 monthly bacteria sampling, annual inspection (internal and external), annual cleaning and disinfection of drinking water tanks. This is no hard and fast schedule. It is a realistic approach that is in line with accepted industry standards and if adhered to rigorously, will ensure that most tanks remain in service for the majority of their design life.
Water tank maintenance tips can only be helpful if they result in the implementation of action. Schedule the reminders, record the results, and address the small issues before they turn into large ones. Your water tank will not thank you, but it will not let you down.
