Drinking water storage? If you're going to do it, do it properly!

Until a few years ago, drinking water storage tanks were considered the ultimate solution for heating drinking water, and even today they are still widely used in private households. And who can blame them? After all, they offer a comparatively high level of convenience with little technical effort and are available at a reasonable price.

However, with the advent of solar systems, there was a need to lower the return temperatures to the heating system as much as possible. And at around the same time, the issue of legionella arose. Both factors spoke in favour of using solar systems.

However, with the advent of solar systems, it became necessary to lower the return temperatures to the heating system as much as possible. At around the same time, the issue of Legionella bacteria arose. Both factors spoke in favour of instantaneous water heater systems, hygienic storage tanks with corrugated pipe heat exchangers and fresh water stations. But is this extra effort always justified, and does it not also bring other disadvantages?

Most drinking water storage tanks are enamelled steel tanks. Enamel is a glass-like coating that is never free of cracks. Therefore, the installation of sacrificial anodes for corrosion protection is essential.

These must be serviced regularly, which is usually neglected or fails if the thread of the anode is already corroded. The service life of the anode depends both on the amount of water used and on the quality of the anode. These must be maintained regularly, which is usually not done or fails if the thread of the anode is already corroded. The service life of the anode depends both on the water quality and the quality of the enamel coating: the more cracks it has, the faster the anode dissolves. An annual inspection is therefore absolutely necessary. These costs must be added to the purchase price in order to make it comparable. However, if this inspection is not carried out, a harmful mixture of rust and metal particles forms in the tank. To be fair, these costs must be added to the purchase price in order to make it comparable.

However, if this check is not carried out, a harmful mixture of corrosion residues and limescale forms in the tank. Water containing limescale is usually also corrosive, as the limescale is only dissolved in the water by acid. If the lime precipitates during heating, the pH value of the water drops – it becomes acidic and attacks the steel.

But that’s not all: the enamel coating also hinders heat transfer, as can be easily determined by comparing the surface area of the heat exchangers. It also doubles the weight of the storage tank and makes it very sensitive to impacts, which are particularly likely to occur during transport.