Increase water main pipe size

Originally Posted by Renomaster

My water main pipe size is 19mm(3/4") all the way(both come into and out of water meter), then for each branch is 12.7mm(1/2"). I am already experience the low water pressure problem at the moment, for example when someone is showering, if another person flush the toilet, then the water in shower room become hot suddenly. My HWS is electric roof storage. Plan to add an bathroom and kitchen in granny flat, one of the plumber come and said need upgrade my water main size to 40mm, then can branch a 20mm water pipe to granny flat, it sounds not bad to me if it can fix the problem. However I am wondering about if the pipe size (from street to the meter) is only about 20mm, will it still useful by just upgrade pipe size in side my property? If not, who should I call to increase the pipe size between street and meter? how much it will cost? if increase the pipe size from the street is not possible, any other idea?

You will get some benefit from a 40mm property service but as you say, without getting a new Council service, it will not be of any great advantage.

It will also depend on what piping you presently have, if for example you have old galvanised then it will be rusted up inside and slowing the flow, and also the supply pressure of the

Council service, and you may also have what a lot of properties have where one 20mm service supplies two properties..

Why not try the new property service first, then, if you are still not happy, get a new larger Council supply.

Talk to your local Council for cost and feasibility..

Thanks Cyclic, I believe all the pipes inside my property is copper. To increase the main water pipe size within my property, does that means I need ask SA water to change the water meter first? As if the water meter's outlet is only around 20mm, how to connect a 40mm pipe to it? Thanks for your suggestions, I will call council first, as I need to know whether there is a feasible also affordable solution or not first, otherwise I may just give up the plan, don't even bother to upgrade the pipe in my property.

You might also want to check how far each 1/2 inch branch is. In QLD I think it can be no longer than 3 mt to the fixture from the main line.

Thanks Ringtail.
Really, only 3 meter. Some of mine are more than 7-8 meters, as the main line (3/4") is laid around my house, then any pipe goes into the house is 1/2", therefore due to the distance, some of them has to be longer than 3 meters. Like the one in my kitchen, the 1/2" goes up against the external wall to the ceiling, across the bathroom, then goes down to kitchen, I think at least 8 meters. But sine the the water main is only 3/4", it's not possible to branch another 3/4" pipe to kitchen, I think it will make the rest of the system even more struggling. That's why I think upgrade the main pipe might be the only solution. Maybe install a water pump to increase the pressure also helps, however that might increase the running cost and noise as well in long term.

Wow ! thats a long run for 1/2 inch. If it were in QLD, 3/4 would have to continue to within (and preferably closer) than 3 mt of the kitchen (or any other) fixture before dropping down to 1/2 inch. Don't underestimate the effect long runs of narrow pipe have of volume. Just the friction alone reduces volume ( not necessarily pressure) heaps. Rule of thumb, the longer the run the bigger the pipe. And remember, pressure is the same or near enough to it throughout the entire system regardless of pipe size. Volume is what you are chasing, and that means bigger pipes, unfortunately. 3/4 should be fine if its run close enough to fixture and providing the pressure and volume from the mains is adequate.