Balanced pressure: Q&A

This is part 4 of a four-part article which has to be read together for the full presentation.

• • If a 15mm main supply to a geyser is 15mm and then from the PRV is 22mm, is that considered balanced?
  • What is the minimum diameter of the piping Council must consider supply before the meter?
  • What causes water hammering

Q: If a 15mm main supply to a geyser is 15mm and then from the PRV is 22mm, is that considered balanced?

A: “Without actually looking at the installation and doing the calculations it is impossible to determine that – you’d need to actually do the calculations and see what it is supplying on a case-by-case basis; what the demand is versus what the flow rate is likely to be. It’s impossible to say otherwise: it would need to be worked out on an individual basis,” says Richard Bailie, member of PIRB’s technical advisory committee and IOPSA compliance auditor.

Q: What is the minimum diameter of the piping Council must consider supply before the meter?

A: “That’s always a contentious issue. In a lot of older properties and a lot of older erfs there are half-inch copper supplies. If you do the math it’s probably not enough. In a case like that we can’t try solve the world’s problems, we are only able to do what we are able to do. If a plumber has done what’s necessary in terms of sizing the pipes correctly within the property, and the homeowner still experiences issues, then the plumber can go to the homeowner and say, ‘we suspect that the problem is from the Council, so please approach them and have them upsize your meter’. But if you (the plumber) just take for granted that the Council’s pipe is half inch, so what’s the use of me trying to plumb this place properly? If you then just plumb the rest in half inch you’ll be doing yourself a disservice. Granted, sometimes the municipal supplies are not big enough to properly supply a property. But it’s not to say that we should then downgrade our installation to suit that because to upgrade a Council meter supply is quite easy, pricey but easy.”

Q: I was told that a stopcock between the geyser and PRV is not acceptable, but using a lever ball valve was okay. Is this true or false?

A: “That is false. It is not allowed, whether a ball valve, stopcock, non-return valve, or anything that can stop flow in any condition. I understand the argument behind ball valves, which is that if it’s open it’s a free flow back and forth. But what if it’s closed? And so it’s not allowed, period.”

Q: What causes water hammering?

“Have you got another three or four hours? That’s a big question. Any plumber will agree with me that it depends on so many things that I wouldn’t even attempt to start going into water hammer right now,” says Bailie.

Written by Eamonn Ryan based on an IOPSA Tech Talk by Richard Bailie on Balanced pressure