Utter pish I went right. I never ever told a lie and I'm shy .
They need a trial of a week. First day. Clean out van then tightness test. If they just hide the mess in van and are done in 30 sexonds probably a twonk. Empty it out sweep it and put it all back = get rid of mrs they can move in.
Need a week to clean out your van pal.
I went right too, not because I'm a liar, just down to the simpe fact I used my right hand and naturally brought the tail to the right. Maybe I'm telling porkies.
As for the OP question. You got it wrong with the last apprentice, so this time follow your gut instinct and forget all else.
Problem solving in the plumbing and heating game is about the knowledge you impart upon the "new boy" and his ability to retain said knowledge, so the enthusiasm you show for the job rubs off on the spotty one.
The rest will come in time.
A weeks trial is no good, you've got to give them time to settle and then it'll "click"
Get talking the the newbie, once he's settled, about the different type of piping plans, plus s and y plan and system design.
Give him a bit of easy system design homework.
If it were I, I'd want the lad to be able to walk into a property establish the system design, and in his minds eye, strip away the walls and floors so that that design is cleary seen in his minds eye.
Why?
Using this forum, the above seems , to me to be, the biggest stumbling block for guys that have been in the trade, even for a few years, going on the questions posed to the forum that is.
Your keeness rubs off.
Why not go for the most nervous lad that looks as if he's been up all night worrying about the interview. He just might be the one how will apply himself most.