Myth: The hardness of tap water must be at least 5.6 dH

The Drinking Water Decree states that water companies must not reduce the hardness of drinking water to below 5.6^odH.

Nevertheless, the Vitens, amongst others, supplies tap water with a much lower hardness level. For example, in Epe. In some places there, the water hardness is 2.7^odH. Find out the hardness of postcode 8161 BL here. The water hardness there is so low because the pumped groundwater is naturally very soft, and there is absolutely no reason to increase this hardness to, say, 5.6^odH.

Drinking water quality standards

Water Work Sheet 4.6, published by the Association of Drinking Water Companies, states:

The treated water must comply with the quality requirements set out in the
Drinking Water Decree, Annex A.

And Appendix A states that the hardness must be at least 5.6^oIt must be dH. We don’t know why this is the case; we have contacted several water companies but have never received a clear answer. Once again, they supply water with a much lower hardness level without any objection, but do not soften it themselves beyond 5.6.^odH.

Whatever the reason, the criteria applied by water companies do not apply to private individuals. The Waterwerkblad (Worksheet 4.6.4, January 2017) states:

4. Criteria for the softening of drinking water
4.2 Domestic installations
A monitoring programme is not required for domestic installations, nor are there any specific requirements regarding drinking water quality.

You can therefore soften your tap water to 0.0 without any concerns^odH.

Conclusion: According to their own standards, drinking water companies must not soften water beyond 5.6 ^odH, but they are allowed to supply it and they do. We do understand that, as there is absolutely no reason to advise against removing limescale from water. Nor are there any health-related reasons; if you’d like to know more about this, please click here.

Incidentally, if desired, our water softeners can be set to a residual hardness of 1, 2 or 3^oThe dH can be set up without any problems. All our devices are fitted with what is known as a mixing valve. But we wouldn’t recommend that, as you’ll still end up with a bit of limescale and there’s absolutely no reason for it.

How hard is your tap water?

Would you like to know how hard the tap water is at your home? Check the water hardness page how high the water hardness is in your town or local authority area.