An independent report, commissioned by Fair Pint, has claimed that the accuracy of Brulines beer flow monitoring equipment is "questionable" because it can not distinguish between beer and water.
But Brulines has insisted that its equipment is "accurate and reliable".
The report said the "performance of the meter is not consistent" and can give a variance of between 8% and 45%.
But it said its observations were "limited" and involved small volumes and "therefore the percentage difference is large".
The report was compiled by SGS, which describes itself as a "global leader and innovator in inspection, verification, testing and certification services".
It undertook tests of the Brulines monitoring systems at the Eagle House pub in Battersea from 27 April to 5 July — an Enterprise leasehold pub run by Fair Pint members Dave Law and Simon Clarke — and at its own lab.
The report concluded that the standard Brulines wheel type turbine device, manufactured by Titan Enterprises, was "not able to distinguish between different liquids" and it found this to be a "major source of error" because of volumes attributed to line cleaning.
"The determination of line cleaning volumes on cask beers is not based on any physical measurement which results in the potential for significant errors in the variance value," it said.
"Note that the type of meter used to monitor beer flow will continue to register if a different liquid (ie water or cleaning solution) is passed through it.
"Given sufficient flow velocity, the meter will also register air/gas flow. gas trapped in the flowing liquid will also be registered."
But the report said that "with keg beers this should not be an issue as the dedicated water meter should give reasonable guidance as to when line cleaning took place and the volumes involved", although some variance was also found.
It also said that there "does not appear to be an adequate calibration routine".
It added: "Overall, it is concluded that the accuracy of the variance figure is questionable, due to issues with the flow monitoring measurement system and the manner by which line cleaning volume is attributed."
Brulines response
Brulines chief executive James Dickson said: "We have had a number of independent tests done over the years and the bottom-line is that our equipment is accurate and reliable.
"Our job is to provide operational transparency and the facts speak for themselves. "Occasionally, there has been human error and we have have the integrity to admit this — integrity is important to us.
"But in the 500 times issues have been to court, we have not lost a case."
Dickson added that often when tenants dispute buying-out evidence provided by Brulines the arrival of a new tenant saw volume performance improve.
The Morning Advertiser would like to clarify that Brulines has not lost a case at court.