And i have heard stuff in hot water tanks cant be good for the fish anyway.
Much of this depends on the storage system for your hot water. Different countries use different systems, what's common in one is unheard of in another. Loft storage tanks are unheard of in the U.S. I wouldn't use water from one of these in an aquarium.
What is common here is gas fired water heaters kept under mains pressure. This is fine for aquariums, I, as well as everyone I know has one & uses it for water changes. Everyone I know have multiple tanks & does larger water changes.
You can get faucet adapters to attach a hose to a faucet at most any hardware or diy store. I have a Y adapter with shutoffs attached to my faucet. I adjust the temp with the one side at the sink, shut it off & turn on the side to the hose. There is another shutoff at the end of the hose, I go into the fishroom & start filling.