Difference between city water meter and apartment water meter

Hello,

we have read the meters for 2015. There are 2 residential units and we do our own service charge billing. There is a water meter from the city located in the utility room. In the two apartments, we each had a meter (hot/cold) from Deltamess installed. These are located in the bathroom.

In 2014, we had about 10 cbm difference compared to the city water meter. At that time, the explanation was that the meters were installed later and water was used by the craftsmen during the construction phase (which is okay for me).

Currently, for 2015, there is a new difference of 14 cbm (so a total of 24 cbm for 2 years) compared to the main meter.

Could it be that the Deltamess and city water meters measure differently? Total consumption was 245 cbm in 2015. From what I know from the rental apartment, there were meters in the kitchen; in the new house there are no meters in the kitchen. Could it be that this consumption is not being recorded?

Thank you and Happy New Year

Is there a garden irrigation system? If yes, where does it start from?

Yes, there is one from the EG apartment. Although the house meter would have to apply there. We have had a hedge since the summer and need to water it. We have definitely felt that, so I would rule it out.

There is a water meter of the city located in the utility room. Does anything in the utility room (washing machines) consume water?

That meters measure differently is generally known... the larger the Qn number, the less accurate they become...

Quote:

[*]Oversized meters measure incorrectly - on average about 7% - 10% more is recorded than actually consumed!

No, in the utility room there are buffer tanks and a water softening system. I just remembered, in the guest toilets where the washing machines are also connected, there are no meters either. Can the difference really be that big? I thought all meters were calibrated.