Upgrading pipe sizes

[macackau]

50 l/m and you are having issues with the flow rate with multiple outlets open? Something isn't right here. I don't think it's a pipe upgrade needed. I have several customers with 25 or 32mm MDPE and the rest of the house is all piped in 22mm copper and they have no drop in flow with multiple outlets open. Are the garden taps fed off the balanced supply or before it? Be good to know the flow rate after the combination valve.

 

[fezster]

Garden taps measured before 3 bar PRV.

The washing machine connector just after the PRV (from a washing machine style outlet) gave me 28 l/m.

Some more info about the pipe runs - all are 22mm poly before teeing off to 22mm copper to the showers. First shower is roughly 15m, second is roughly 25m, and last is about 30m pipework.

The dynamic pressure at the shower is what's confused me most. Only half a bar with 18 l/m being delivered. That's a 2.5 bar drop, and increase in height is only 5m (so 0.5 bar drop expected). Yet dynamic pressure at the outside tap (delivering about 25 l/m) is a 0.5 bar drop. Is the dramatic pressure drop an indication of undersized pipework?

 

[fezster]

22 secondary return. Oh dear.

This is what two different plumbers have recommended. Could you elaborate - would you expect it to be bigger? Or smaller?

 

[ShaunCorbs]

This is what two different plumbers have recommended. Could you elaborate - would you expect it to be bigger? Or smaller?

15mm will be fine as long as not stupid distance

 

[fezster]

50 l/m and you are having issues with the flow rate with multiple outlets open? Something isn't right here. I don't think it's a pipe upgrade needed.

Correct me if Im wrong here, but isn't it the dynamic pressure which is the problem, rather than the flow rate. The shower MI state 16 l/m at 0.5 bar. So even though my mains can deliver far in excess of that, isn't it the shower dictating the flow rate, because of the low pressure.

And whilst I havent measured this, with a second shower on, the dynamic pressure probably drops to a paltry 0.1/0.2 bar, and hence flow drop dramatically to both.

I'm not saying I've gotten my head around this completely, but my understanding is that if I can raise the dynamic pressure (by increasing the pipe size), then the shower will have a higher flow rate?

 

[fezster]

15mm will be fine as long as not stupid distance

It's roughly 25m to where the pipe will loop. I think this is why they said 22mm would be better, otherwise I'll need a more beefy bronze pump.

 

[ShaunCorbs]

It's roughly 25m to where the pipe will loop. I think this is why they said 22mm would be better, otherwise I'll need a more beefy bronze pump.

15mm will be fine only needs a flow and stnd 65-150 will be fine

 

[lame plumber]

try some different plumbers, yours dont seem to understand the basics of a secondary return and how it works. So the advice on increases the pipe sizing for little gain will probably be suspect as well.

 

[fezster]

Just now I measured the dynamic pressure on my shower hose outlet with the shower running. The gauge showed just over half a bar. This ties in with the showers MI which quotes 16 l/m at 0.5 bar. Static pressure at the shower is 2.5 bar.

Ok, scrap what I said here. Must have something to do with measuring gauge being on the same shower valve (gauge on hose outlet, with main shower running).

Just redid the dynamic pressure test by running a different shower. Gauge dropped from 2.5 bar to 2.1 bar. Now Im even more confused. What does this mean?

 

[macackau]

It means it's time to get someone in who knows what they are doing.