My kitchen tap is filtered with a pentek 20 micron filter which reduces chlorine taste and odor (completely removes chlorine taste) it is a granular activated carbon filter.my question is can I use it for water changes.thanks.
Check to see if your city uses chloramines and not chlorine to treat the water. But even so, I personally wouldn't trust a micron and carbon filter alone. If you have a 4 or 5 stage RO/DI system with an ion exchange resin as the final stage it should break everything down, but home systems rarely remove all of the chlorine and never completely break down chloramines. I would still treat with a chlorine remover after you refill your tank during a water change.
@Jestep's answer is right. It's a little tricky to say but 20 micron is really pretty big in comparison to anything that an RO/DI filter would remove. Check out the diagram below to see what I mean:
I'd also note that if you're filtering out trace elements you need to make sure you add them back in or your water can become unstable. This is probably irrelevant in your case because it sounds like this filter is more for dragging out larger particles.
Can I use it?
You absolutely can use it but I'd treat it as normal tap water and take the appropriate measures to ensure you remove the chlorine from the water as you normally would.
That won’t make much of a difference to your water changes, but continue doing it. Maybe you could discover a new technique in aquarium care.