Yes, common for PVC is class 0, 6, 7. Class 7 best because very thick. For home use class 7 is more than enough.

PVC Class 7 pipe with proper installation (allow to dry well before use) will be good enough.
If you supply the fittings using screw threads for the joints this will make replacement much much easier in future (especially the ones under kitchen sink/toilet wc/sink) then can use flexihose as necessary, rather than hardcoded fittings that will be size and placement headache for replacement later.
Usually contractor wont do screw fitting because extra few dollars of fittings.
But if you make it such that the output from wall pipe is female screw fitting, then you just connect male to male nipple, with the pipe thread tape (yellow ones from CSM are good), then you can replace anything after that nipple (flexi hose to sink tap or WC) very easily.

Do note fittings are per system (colour), if PVC all grey is grey fittings, if black HDPE or blue MDPE will only take that kind of same colour fittings. Hence it is easier for system compatibility to use all PVC class 7.

This post has been edited by ceo684: Nov 5 2020, 01:27 PM

Thanks for the advices.
Is PVC fittings also come with class 7? As normally the leakage of PVC piping system is on the joints.
Any idea to ensure no leakage on the joints other than the workmanship?

The PVC "chloroform" is pretty good but because it has tendency to push apart (between fitting and pipe) you need to push them together and hold it in at least for 5-10 min for it to properly cure. Not just apply and let it be without holding them in together, the "chloroform" is not instant glue.
It works better if you can leave it overnight or so to fully dry.

Its similar to the curing of concrete, just that it wont take so long like 28 days for concrete to fully cure.