[czrnb]

Thanks for the link!

I don't think it applies in this case however. There is no explicit cognitive bias at play. There would be if he considered his job is as good or better than plumber's (although actually, unless he has a very particular toilet setup, doing a good job after meticulous research and preparation is not out of reach at all).

In any case, even doing an OK job which is definitely worse than a plumber's but holds (and will presumably hold) is still a win if you're short on money but can spare the time/motivation.