Welsh Water profits increased to £50m in 2013/14
Welsh Water recorded profits of £50m last year - up from £29m the year before, its latest figures show.
The results mean 2013/14 was its strongest operational year since it became a non-shareholder-owned company in 2001.
The report shows customers had the lowest average bill increase of all water firms for the fourth year running.
Customer satisfaction was over 90% and 60,000 people get help to pay bills.
The results out on Thursday show the firm invested £354m in capital projects in 2013/14 and a further £344m will be spent in the coming year.
That will include maintaining and upgrading its water mains and sewers and building new water treatments works in Conwy, Ceredigion and on Anglesey.
Money will also be spent on developing techniques, such as RainScape in Llanelli, to help avoid surface and sewer flooding.
The firm's latest results confirmed further improvements in Welsh Water's drinking water quality and showed it achieved the lowest number of serious pollution incidents across England and Wales.
The company said it managed to maintain high levels of service despite the extreme weather conditions last year, including prolonged hot periods and the wettest winter in almost 250 years.
Welsh Water has been owned and managed by not-for-profit company Glas Cymru since 2001 and any profits are put back into the business.