Compound water meter registered a negative flow reading during high flow test

[flowersnvessels]

During a high flow (7000 L/min) fire water pump test, a compound meter connected to the piping system recorded a diminished reading (I.e. Backwards reading). This meter has been installed in the piping for 6 years and has operated properly until now. Why would this meter record a negative reading at this time?

 

[bimr]

Did both high and low meters register negative numbers?

 

[flowersnvessels]

No, the small (low flow) meter registered a positive reading, and the large (high flow) meter registered a negative value.

 

[coloeng]

Is the large meter installed in the right direction? I know it sounds like a no brainer, but I have seen it happen.

 

[flowersnvessels]

Yes the large meter is installed in the right direction. It has been in place for 6 years and during that time it performed as it should.

 

[bimr]

It is not clear how your piping is arranged.

If the fire flow went through the meter, perhaps a valve was opened too quickly or the pump started quickly causing a shock load on the meter that damaged it. In this case, perhaps the meter should be repaired or recalibrated.

If the meter was on piping that did not receive the fire flow, the pump may have created suction on the water system, pulling water backwards through the piping system.