You're talking about old style push fittings that needed the plastic nut being tightened.When you get a quote this info is for everyone, always ask if they are using any push-fit stuff as we got caught out on one of our rnetals when we had a new bathroom inc shower at a rental. The pushfit leaked a couple of days ;ater in the loft of a bungalow and good job I'd gone back to check it ie the new bioiler was working and no leaks re bathroom etc. The gut returned the same day no apogy and muttered "it was loose" - thanfully damaged was limited to a foot square and a bit of zinner pait did the trick a few days later.
Up until that time I thought people installing bathrooms and new boilers only used copper and solder. - guy called him self a "plumber" my foot
I too saw those leak because they were loose.
The new ones are fool proof, as long as you push them in fully and use pipe inserts they never leak.
At least the hep2o that I use, can't comment on other brands, although I haven't come across a leaky one yet.