"The long term cost on the business is greater because they'll have to find a replacement because we don't have any more wine, so we may lose the contract."
He said he was still taking in the full impact of the loss.
"This is the best vintage we've ever seen in Hawke's Bay in my time making wine here," he said.
"The impact on the business long term is so significant."
Mr Barker said the valve had a lock mechanism, which meant it could not have be opened accidently. He believed someone aiming to steal a few litres had misjudged the pressure in the tank.
"It's a two-inch valve, so it's going to knock you off your feet. It's not a garden hose."
The incident had been reported to police, who had been to the winery to look for fingerprints.
"The problem is we couldn't tell if there were vehicle tracks because the merlot had washed away anything that was left."
Mr Barker hoped someone would come forward with information on the culprits, who would have come home covered in red wine.
"Somebody is going to be covered head to toe in pretty dark merlot," he said.
