USI is offering 18p in cash for every Spring Ram share, a 29 per cent premium to the closing price on Wednesday and more than three times its value earlier this year, when the shares plunged to 5p.
The deal marks an achievement for Roger Regan, the father of the young entrepreneur Andrew Regan, whose attempt to take over Co-Operative Wholesale Services failed two years ago.
Roger Regan joined the group as chairman in 1993 and discovered that Spring Ram, a stock market favourite in the Eighties, had overstated its profits due to financial irregularities.
"My achievement is the business hasn't gone belly-up - there are 2,000 people now part of it," he said.
USI, formerly the US wing of Hanson, said it needed to buy a UK base to market Jacuzzis efficiently in the UK.
Currently, its nearest plant is in Italy. David Clarke, chief executive of USI, said he would retain the current management. Spring Ram shares closed up 4p at 18p.