Should be alright using a tee piece plus a tap😉Darran
Yes I have and my PW is also 21 lpm.However on system I have 19mm outlet pipe (mdpe) and use a tee to draw off then another tee as the PW is twin feed. No shortage of water, although it works it way through a 1000 ltrs quickly !!Darran
Depends what pressure washer you use, half inch pipe might not feed it fast enough. I had a T for my Kranzle but it only uses about five litres a minute I seem to remember.