There are few things that inspire terror more in travellers than drinking water in places that do not have the same sanitation standards as back home. Although 94% of the country does have access to piped water, anyone who has been brave enough to take a sip would be quick to inform you that it does have that delicious ol' rusty pipe taste. A delicacy for some but something that most would probably prefer to avoid. Some areas are safer than others but as a rule of thumb, try not to swallow the tap water unless you enjoy frequent trips to the bathroom.
Many hotels will offer you bottled water that comes from sanitised sources that have the ISO 22000 certification for safety. Fantastic, however what you will find while you are on the road is that there are many vendors on the side of the street and on trains where you can purchase bottled water. Most of them will have a double seal which ensures that they haven't been tampered with (the regular lid seal and a soft plastic covering) but it isn't unheard of in Sri Lanka for tampering to occur before they reach these shops. So that water that you purchase may have a false registration number and not actually be as safe as you would hope. Aside from ensuring that you have all your vaccinations in order and a belly made of steel, you may want to add an extra step in your water procurement. Carry more water than you need and only refill in safer environments.
As I mentioned, good hotels usually use reputable brands so filling up at the water stations in these places is better than going to street vendors. This is also a much better option environmentally as Sri Lanka's plastic recycling program is often just a chemical bonfire behind the family home. Single use plastic is one of the primary problems facing the world today. Unfortunately, so is access to safe drinking water. One of the ways that people have solved the water problem is through the delivery of bottled water. As one solution comes into the light, another problem arises. More plastic in the water sources is probably not the best way to build a healthy environment. However, a good middle ground is filling up at your hotel. The large 19 Litre drums of water get dropped off and picked up again, their size makes them good for transport and reuse. Welikande Villas and Trekking Center had this specific concern as travellers would always be purchasing single use plastic drinking water bottles. The guesthouse began giving refillable bottles to guests who go on a trek in the Knuckles Mountain Range. After your stay, you can take your bottle with you and refill it all over Sri Lanka!
Looking after your health while you are abroad is going to be one of your biggest concerns and ensuring that you have a safe drinking water supply while not harming the planet is a wonderful way to enjoy Sri Lanka and ensure that it remains beautiful for many generations to come.