Chlorination and Treatment of Your Cold water Tanks FAQ Clean or Treat ?

Cold Water Storage Tanks :- Loft Tanks, Roof Top Tanks,Boosted basement Supplies and Combined tank & Calorifier.


  1. Tanks should be clean and free from corrosion, scaling, silting and any other debris or contamination that may provide a breeding ground for micro-organisms including Legionella.
  1. Tanks should be fitted with lids that are vented.  These vents should be fitted with rodent screens.
  1. Where possible expansion pipes, from calorifiers, should NOT be returned to cold-water storage tanks.  If they are care should be taken to seal their entrance into the tank to prevent the ingress of dirt or other contamination.
  1. Overflow and warning pipes should be fitted with rodent screens.
  1. Tanks should be well insulated to prevent elevated stored water temperatures.  Stored water temperatures should ideally be maintained at less than 20oC, to prevent the proliferation of micro-organisms including Legionella.
  1. Locating the tank services and makeup pipes on the same side of the tank should be avoided, as this may lead to water stagnation at the other end of the tank.  If there is a possibility of water stagnation occurring, a sparge pipe should be fitted to the services pipe
  1. Tanks should be labelled clearly for easy identification.
Draining and Cleaning out a water tank, is not always the only solution or the best solution to keeping tanks clean. In some care homes and hospitals it is just not possible or practical to switch off the water. The yearly inspection would normally mean cleaning out and the sterallisation of the tanks with Chlorine (AKA Bleach). A chemical; Sodium dichloroisocyanurate (NaDCC)  that has been used by hikers, soldiers and disaster relief agency s is now being made in large quantities that has seen the price of this chemical come down, to a price equal  to chlorine water treatment and it is, by far, a much safe and more useful chemical to treat your companies water tanks and drinking and bathing water systems.
Water Tank Cleaning & sampling in a Box £55 +vat enough for 1000 ltrs or 2 standard tanks
Tabs and water sample bottle return pre-paid postage and instructions risk assessment and COSHH sheets

Cold Water Storage Tanks in themselves, present a low Legionella risk in general terms.  However, where the tanked water supplies other plant that have a high risk factor (e.g. cooling towers, showers etc.) the potential risk of such tanks is much higher.

Poor control over the water temperature and condition of the stored water plus the condition of the tank itself, may lead to very small levels of Legionella colonising the tank and, therefore, producing a possible source for the bacteria to infect other water services down stream.

According to medical experts, drinking water contaminated with Legionella is not expected to allow the development of Legionnaires Disease.  There are, however, other bacteria that can colonise water systems and lead to risk to employees and others.

It is important to note that is general terms you keep stored water clean because of bacteria and not legionella colonisation.  That is why a Total Viable (Bacteria ) Colony Counts (TACC or TVC) water test should be taken from your stored water every year.

Using Na DCC to treat your water tanks, saving time, money, less risk and much safer.

This not a new water treatment compound, it is that it is now used in such quantities that the cost has fallen to a point that using it commercially is possible. The main advantage of Na DCC is it is added, and remains in the water tanks and circulates through the whole water system.. It  has the benefit of steralising every drop of water in your buildings system:- pipes, taps, shower-heads, filter housings etc. This is a very safe treatment and used by millions of people every day to keep there drinking and bathing water safe  for them to use. It is a vital tool  in disaster zones, camps and by travels to keep water clean and free from any bacteria capable of making you ill

One Tab treats 25 Ltrs so your average tank needs only 20 tabs or 3.3 gms of Na DCC and at £25 for a Alegion Water Treatment dosing kit, it will save GP`s, Dentists, Care Home owners a fair bit over the years.

Its easy to order  one of our kits. Full instructions are given and if you can make a cup of coffee you are capable of dosing a your water tanks. Just email me, tell me the dimensions of your cold water tank (in your risk assessment or measure the tank:- HxWxL)  I will then send you measured dose of Na DCC specifically for your water tank or tanks. A water TACC test is included. This is to analysis you stored water the day after treatment. This will show you the treatment was effective and it will complete your yearly ACoP L8 tank inspection.

I would add not all tanks will, only require Na DCC dosing.  If the only remedial work you can achieve is, dosing your water tanks, (until such time as you can, plan for a replacement tank, thorough clean or other vital works) please consider using an Alegion Water Tank Treatment Pack. Its a good "stop gap" and will buy time. Its better than doing nothing and any remediation dosing you do, will improve your water quality if only for a limited time.

 Alegion Water Ltd Na DCC tank treatment and TACC water analysis box 1000 ltrs £55+ vat


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