Severn Trent shares rose 1.7% after it said underlying pre-tax profits rose 4.3% to Â£525m, helped by fewer leaks following an investment programme.
Severn was one of the biggest risers on the FTSE 100, with the index up 4.36 points at 7,500.70 in early trade.
EasyJet was the biggest riser in the FTSE 100 following a broker upgrade.
Shares in the airline climbed 1.9% after RBC Capital Markets raised its rating on the company to "sector perform", arguing it was "increasingly probable EasyJet has reached its profit nadir".
After a strong performance on Monday, Marks and Spencer fell back, dropping 1.7%. The High Street retail giant is due to report its full-year results on Wednesday.
On the currency markets, the pound slipped 0.1% against the dollar to $1.2987, and was down 0.2% against the euro to 1.1540 euros.
London's stock market edged higher, with shares in Severn Trent rising after the water company reported an increase in full-year profits.