I like:
HDPE, especially Buteline system
PPR
(But both these types need proper tools to install)

I'm ambivalent:
PVC, but only choose the good grade.

I dislike:
Copper - expensive, joints can leak, can corrode depending on the chlorine in the water
Stainless steel - expensive, difficult to work with regards to cutting, threading, jointing

I really dislike:
ABS - leach chemicals, long solvent curing time, more expensive than PVC
GI - Will rust over time for sure.

I agree, but please choose pipe that conforms to SIRIM standard if plumbing a bathroom with buried pipes. I believe that means the pipes will be rated PN12.5 or above.
(PN = Maximum pressure rating, in Bar. 1 Bar ≈ 14.5 psi)
Pressure rating depends on the thickness of the pipe walls, which in turn determines if the joint fittings fit and seal well without leaking or not.

I think HDPE pipe is suitable to be concealed.
1. The pipes are slightly smaller than the equivalent PVC pipe.
2. The joints are smaller than PVC joints.

3. You can get straight pipes in lengths of 4 5 m, or go for a whole 100 m roll.
4. There are suitable mounted threaded connectors to fix your taps

5. The pipe is flexible, so will absorb slight wall movement or foundation settling
6. Water hammer noise is reduced
7. Available with pressure ratings up to PN20
8. Easy to work with, no solvent, joints are immediate.

It's not a perfect system though. Bad points are :
1. You need special crimpers. Each size is ~RM 210 - RM 300, usually 3 crimpers needed
2. You can't joint close to the wall/edge, as you minimum need the space for the crimper to make the joint
3. Not everyone can install due to the requirements of tools
4. I don't think it is prohibitively expensive, but it is more expensive than PVC
(Example of the elbow joints in the picture above.... PVC cost RM 0.60 , HDPE cost RM 2.40)
5. For wet areas the aluminium part of the joints need protection with self sealing tape

Full disclosure : I am not a plumber. But I am doing up my own place by myself as a "hobby" project. I have pressure tested the HDPE pipes I installed to 150 psi and all looks good. (Bought the crimpers and a pressure pump) I do help out friends and family who have plumbing problems, and I always use HDPE when I can. So far none of the things I have done have failed, but who knows 10 years down the line. The above points are strictly my experience using HDPE pipe for plumbing, and does not constitute an endorsement or a recommendation. YMMV.


This post has been edited by stormer.lyn: Oct 7 2022, 10:46 PM

Honestly, this HDPE pipe use is getting more common in the KV, as it is a good, almost fool proof system. Just search your favourite online shopping platform for "Buteline" and you will be able to see what is on offer. Contact a plumber, and ask if they install this same name plumbing.

I still use "Hansen" fittings, or those giant Poly O-ringed compression fittings in certain locations, like at the outdoor water filter. So just mix-and-match as you need.

This Sh*pee store has some pictures of the installations https://shopee.com.my/BUTELINE-FITTING-ELBO...753.12119930309 (Absolutely no link to me, just an example of installation and prices)

I 100% agree with you. I just want to point out that the pressure does not drop, the flow rate does. After all, 3 bar through a straw is the same as 3 bar through a 20 mm pipe. But you wouldn't be satisfied with a shower with the water coming from that straw.

I notice that piping in M'sia is done without any concept of water flow rate. One small pipe branches off to 2 small pipes, or an entire bathroom is fed by a small pipe. No wonder as soon as you turn on a tap, the shower water slows. And then to get a better flow rate, add on a booster pump, and set the pump to high pressure. No wonder everything starts leaking after some time.

Just think of a bucket of water dumped on your head, versus that same bucket hanging over your head with just a small hole dribbling water. Which would you rather bathe in?

My conclusion is that water supply pipes should be well designed also, with as few turns as possible, and with proper sizing in mind, no matter what type of material is used.

I don't think PEX is all that available in M'sia