Firstly I must acknowledge Pakistan is way behind from providing clean water to every citizen.
There is a kind of race that started about 5 years ago among politicians and corporate tycoons to provide clean water to improve their image. More and more, bigger and better water filtration plants are coming up just about everywhere with a huge board besides who granted it for free. It has become like a media campaign. Now water filtration plants are not really that expensive in Pakistan and it makes for huge publicity.
There are helping factors to that. Firstly population in Pakistan appreciates clean water for some reason. There maybe religious reasons to it but it is something they will be obliged by. Mushshraf started to import and then attracted quite a few water purification brands into establishing plants here in Pakistan. These plants are manufactured or atleast can be supported locally. There is fierce competition for market share means low prices.
Then canal system of Pakistan is one of a kind. Probably largest in the world. So fresh water is easy to get from a canal to a plant which themselves are cheaper. Next blessing came in the form of Power outages. Yes, I mean it. As people turned to alternate sources to power their houses. Markets were flooded with solar panels with ever dropping prices. With solar panels, politicians could now stick in a small water purification plant with solar panels on top in a far flung village with a huge board with his picture reminding constantly who to vote next election. Who cares? At least there is clean water. Looking at the popularity Punjab government and Balochistan government with help of NGOs started giving solar powered filtration plants free or at nominal rates through their MPs basically to boost their political image.
As I said, we are way far from ideal but people's desire for clean water and politician's / business tycoon's desire to gain popularity has really helped here.