Browse Forums Building Standards; Getting It Right! 1 Sep 02, 2011 2:19 pm We are putting together the specifications for our new house and I wanted to ask the plumbers here their thoughts on pipe sizing. When our current house was being built (20+ years ago) for reasons that escape the foggy recesses of my memory we ended up with the main water inlet pipe at the house at the minimum that it could be, whereas it was supposed to of been a larger size. What is the "standard" pipe size for the internal plumbing, and what would be an "upgrade" size ? I ask this as we are going to have a double shower / washing machine / dishwasher and want to be able to run any combination of these without, as currently happens, a large drop in flow / pressure when a second service opens or loo is flushed. While I realise the mains service will have a pressure-limiting valve fitted, it does appear to be quite a large diameter plastic pipe, and if nothing else, if I cannot have "unlimited" pressure, I sure don't want to lose any volume when additional loads kick in !! I am still considering whether or not to go copper for all the internal piping, would this make a difference, would it be a good idea to specify a large (external) plastic size to where the service actually enters the home ? Thanks, P_D . Block settled 07 June 2011 Our little piece of the Interwebs on HomeOne....... viewtopic.php?f=31&t=48577&start=0 Re: Plumbing specs - Pipe sizes 2Sep 08, 2011 6:01 pm A couple of caveats: I'm not a plumber so you should get advice from those who have insurance. Its an interesting question for many reasons. I'm adding some thoughts because none have and I have plumbed in a bit a of pipe over the years. You are on the right track. My experience suggest that mains pressure is the issue more than pipe size. Firstly no need to go copper nothing gained, PEX is fine. The standard internal pipe for hot and cold water is around 13mm (1/2 inch) ID. Next size up is 3/4inch. As soon you you drop to 1/2inch pipe inside the house, pressure will drop if showering and dunnie flushes. So you could run 3/4 inch internal and branch off to 1/2 inch to each room. Not too unusual. You could also possibly add an inline pump to improve pressure if worried. 1 inch supply to house should be fine assuming not a long run. Unrestricted pressure has its own problems. Good luck Pulpo Re: Plumbing specs - Pipe sizes 4Sep 09, 2011 12:15 pm Would it be OK if I had them run 3/4" as a "main" and ran a dropper of 1/2" to each and every service, or at least the showers ? If each shower was fed via the 3/4" main - 1/2" dropper, would that be sufficient to guarantee maximum flow to the shower(s) when another service (dishwasher / washing machine) cuts in ? I guess it doesn't really matter if these other services suffer a pressure / flow drop as long as the showers keep up with the demand ? Thanks, P_D . Block settled 07 June 2011 Our little piece of the Interwebs on HomeOne....... viewtopic.php?f=31&t=48577&start=0 Re: Plumbing specs - Pipe sizes 5Sep 09, 2011 1:02 pm because the distance is short in the 12mm it doesn't effect overall pressure much. The reason it suggest making sure the main run is 3/4 is because most of the loss occurs over the 20meter or so run. Because everyone service eventually feeds off this, by changing (or making sure) that the pipe is upgraded then all service get the benefit for only a small relative cost. OK it's been a little while! I've been busy getting time where I can to work on this. I started by grading a pad (borrowing a… 26 19952 I have a box of quality drill bits that seem to be new but their engraved sizes covered by rust ,,,,I tried to sand them to see their sizes but still I am finding… 0 1429 yep sounds good make the footing bigger to to allow for the pipe in the middle 3 7297 |