Here is an article and some videos showing how a flow meter can installed incorrectly:
https://gsvit.wordpress.com/2016/04/19/how-to-overestimate-water-flux-by-wrongly-positioning-an-instrument/ Figure 4 shows how to correct the problem. As far as I know, Rossi had these same problems, and he did not install the kind of plumbing shown in Fig. 4 that would fix them. The instructions for the meter are here: https://gsvit.files.wordpress.com/2016/04/istruzioni-per-la-corretta-installazione-contatori-unico-e-multiplo.pdf Concluding sentence: N.B. Per mantenere il buon funzionamento dei componenti del contatore, si raccomanda di assicurarsi che il contatore sia sempre pieno d'acqua (ad eccezione di brevi periodi dovuti a manutenzione). Google translate: N.B. To maintain the proper functioning of the meter components, it is recommended make sure that the counter is always full of water (except for short periods due to maintenance). - Jed
