hi all, so i've read various how to's on changing sand in a sand filter. So, once i've taped the centre pipe with tape, filled the filter half way with water so the sand doesn't impact on the laterals, do i fill it again with water before i put the multiport in?
No need to really change the sand, but if its empty now, that is the process yes, some even put pea gravel in bottom until its just over the laterals. Fill the sand to the shoulder of the filter, that is where it first starts to make its turn to narrow up. This gives you the largest square footage for the water to be filtered through. No need to fill it with water before putting multiport on, it will fill with water once you turn pump on.
To answer the question first asked, no you do not need to add more water after filling the tank with the correct amount of sand. The initial dose of water was to reduce impact on laterals while adding the first few bags of sand.