Stainless steel pipe was much better for last longer then were using PVC pipe of the interior pipe can easily clogging like jelly else.

But using pump can help up to clean interior pipe as well, cause the water pressure maybe runing more stronger.

If it is just cold water, normal PVC pipe will do, you can opt for thicker one also.
But if there is solar heater or heater storage , then may consider polyurethane pipe.

you can opt for polypipe by kindratech and use compression fitting

works very well for me..

i opt for polypipe with "thick" walls not those cheap not SIRIM certified..
and use Hansen fittings (http://www.sansico.com.my/)

redid my whole hse pipe to poly.. from the old metal type..