may be the pressure is so low that it is beyond the sensitivity of the pressure gauge.

Hi Foroogh and all.

Few possibilities:

1 - Are you 100 % sure water is flowing?

2 – May be water is flowing at a very low flow rate so that the pressure drop downstream of the gage is too small to be registered.

3 – The tee vertical tap connecting the gage may be blocked.

4 – The gage itself is somehow deranged.

Dear R. P. Peçanha and Manjur Rahaman ,

Thank you so much for your response and help.

I have to check the tee vertical tap! Probably it is blocked because my negative oil pressure gauge (200 mbar to 1 bar) also does not show any change when the vacuum pump is run.

Best wishes

Dear R. P. Peçanha and Manjur Rahaman ,

Thank you so much for your response and help.

I have to check the tee vertical tap! Probably it is blocked because my negative oil pressure gauge (200 milibar to 1 bar) also does not show any change when the vacuum pump is run.

Best wishes