Pipe size length bends junctions to Combi - affect on water flow rate?

[Timmy D]

Whatever way it’s piped, opening another outlet will reduce the available flow to the boiler/other outlets.

Nothing you do to the piping will make a worthwhile difference.

If you want more flow rate, you need to get more from the street.

 

[Andy VC]

Problem might be with the poly pipe internal diameter, if you can measure the OD then ID can be determined, a pressure gauge reading, even static, taken anywhere would be a help as well, also estimated distance from mains stopcock to your house.

Bit of a delay, but now double checked, and found marking on black poly pipe - looks like "TELCON BS 1972 ...CLASS D". Old Alkathene pipe?! Must be the 1/2 inch OD, which from what I have found is just 14.1 mm ID.

A water authority guy was looking at stop tap at water meter a couple of weeks back and he did a pressure test at an outside tap for me and it was just about 3 bar. Distance from mains stopcock to internal stopcock, in kitchen at the far side of the house, is about 16 metres.

I assume the problem is with the poly pipe internal diameter then ??

 

[Andy VC]

Just to clarify what I have now found with regards to drop in water flow as other cold outlets are used, as a number of you have made clear is an issue (thanks to all for steering me in the right direction):
Flow at, for example, utility sink cold, by self, 18 lpm.
Also turn on bath cold, flow at utility sink drops immediately to 12 lpm.
Turn on 2 more taps, flow now down to 10 lpm.
Turn on 2 more (utility plus all other sinks/bath), flow down to 8 lpm at utility sink (and bare dribble out of upstairs bathroom sink).

[PS. if wondering why I seem to be a bit unsure about current pipework setup, or surprised that water flow drops so much with just a couple of cold outlets running, it's because we haven't actually managed to move in to this house yet as there have been a few unexpected issues that need sorting before we can, including sorting out various water damage issues (!), and installing new boiler, replacing radiators etc. and now perhaps sorting incoming pipe from water meter!? Therefore I am just really discovering how the water setup is working, or NOT working very well (compared to what I have experienced before)]

 

[Andy VC]

If you want more flow rate, you need to get more from the street.

Looks like that may be the only answer.

About 16 meters away; inside the house the current 1/2 inch pipe runs under the suspended timber floor, then outside there is 6 meters or so to external stopcock at water meter (under garden, and then less than meter of path, which looks like it was previously dug up, probably to put in the water meter at some point.)

Is that a big/expensive job?

 

[John.g]

I have similar pipework in a 1971 built hose but its a measured 21mm OD X 11.5mm ID, its 1/2" (imperial) so 1/2" ID, nominally. If yours is 1/2" ID then it can't be 14.2mm ID? except you measured this.
I have a 21M run of this and I get measured static/dynamic pressures of 3.6/0.95 bar, measured on a outside tap at a bath (3/4") tap flow of 14.4LPM. Theoretically, re pipe loss calcs, the pipe friction loss should only be 1.16 bar, ie static/dynamic of 3.6/2.44 bar but of course, as in all cases, I don't know if the pressure at the mains stopcock is a dynamic 3.6M, it may well fall as well, depending on the mains supply pipe diameter.

Anyway using the pipe loss calculations, and if you accept that the pipe ID is probably 11.5mm or thereabouts then a flowrate of 16LPM will result in a pipe loss of 1.07 bar and theoretically leave you with a pressure of 1.93 bar, (3.0-1.07) at the end of the 16M run.
You have no control over the mains pressure but of course you can renew the 16M run in 3/4" or 1" ID, ~ 28mm or 34mm OD, the equivalent pipe losses are then negligible at 0.09bar&0.02bar and are still only 0.3bar/0.08bar at a flow rate of of 30LPM. (at the end of the 16M run).

Friction Loss Calculator - National Pump & Energy

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[ShaunCorbs]

Even with a new supply the water might drop eg won’t stay at a solid 16lpm as the water services in the area might not be upto all capacity etc

Tbh new 25mm water service and install an accumulator

 

[Andy VC]

Even with a new supply the water might drop eg won’t stay at a solid 16lpm as the water services in the area might not be upto all capacity etc

Tbh new 25mm water service and install an accumulator

Replace supply pipe with 25mm (ID or OD?) ? AND put in accumulator (had not thought of that) ?

 

[Andy VC]

Note, I'm having problems replying to some people's posts ...

 

[John.g]

GB pipework is metric (unlike ours which is still imperial) so 25mm is probably ~ 19mm ID or(3/4"), you can look up a table to give you the relevant numbers but probably not a huge difference in installation cost if going for a larger diameter.
There are two types of accumulator, one builds up a accumulated vol when pressure rises due to reduction in demand, the other is a pumped type.
Suggest buying a pressure gauge that you can stick on the end of a outside tap and monitor the pressure over various usages/times before making any decisions.

 

[Andy VC]

Many thanks for everyone's advice and comments. I think I have a better understanding of the issues now, even though I am not sure of the best way to move forward to improve the situation!

Thanks for now.