Accumulator - benefits?

[hazetimesfive]

30lpm showers. a bit excessive don't you think?

why not fit flow limiters to the showers and save the environment, new builds are designed around 125 litres per person per day. One of you showers uses that in less than 4 minutes.

 

[fezster]

These are the valves I have:

http://www.purabathrooms.co.uk/catalog/showers/showers-thermostatic-concealed-shower-valves/BQ333

Don't all valves of this type deliver similar performance?

 

[hazetimesfive]

have you actually measured the output of the showers

 

[fezster]

No, not yet. I have experimented with running multiple showers and seeing the output drop (not sure if this is flow dropping or pressure dropping or both!). I will get a bucket and do some measurements.

 

[fezster]

Done some measurements. It's not as easy as it looks. Ended up getting drenched!

Measured 3 outlets at a time, and repeated the test twice. By far the highest output is from the outside tap. This is also the hardest to measure using a 1.5 litre jug!

Results:

First test:
Outside tap - 1.2 litres in 2.9s.
Utility - 1 litre in 9s.
Ensuite shower - 1 litre in 13s.

I make this to be 30 litres/min.

Second test:
Outside tap - 1.4 litres in 3s.
Utility - 1 litre in 13s.
Kitchen - 1 litre in 10s.

which gives 38 litres/min.

I then measured just the outside tap in a bucket, and got 9.4 litres in 18s, which is 31 l/m.

I think overall it's probably about 40 - 42 l/m.

This points to my overall flow not being enough to drive 2 showers according to the shower spec. However, I also measured just the shower on it's own, and got 3.8 litres in 18s which is only 13 l/m. Nowhere near the 32 l/m the instructions state.

With the outside tap running, the shower gives me 1.4 litres in 11.5s which is 7.3 l/m. This felt similar to when I have a second shower running.

Not sure what to make of all of this. Is the pipesize to the showers the restriction? Or is the mains the restriction?

Not sure if I mentioned before, and Im wondering whether it's pressure rather than flow which is the problem - but I measured pressure at 4 bar static at outside tap, and drops to 3.5 bar dynamic with another outlet open. This is bypassing my 3 bar PRV. I tried to measure pressure on shower, but Im not sure it's entirely accurate because of the attachment I had to use. It read less than 3 bar static. There's approximately 15m of 22mm pipework to the first shower.

 

[fezster]

Yet more tests today. But here's the most useful ones (I think):

1)
Upstairs bath hot and cold - 20.6 l/m
Just hot - 15 l/m
Just cold - 15 l/m

2)
Bath taps + sink mixer tap + ensuite mixer tap - 29.6 l/m

This tells me the upstairs is getting up to 30 l/m. Yet the bath tap with hot and cold only delivers 20.6 l/m. It's a mixer tap but with individual hot and cold controls. The sink taps are mixer taps with a single control.

I also took the heads off the showers and measured 18 l/m in ensuite and 21 l/m in bathroom individually. Combined I measured 27.5 l/m.

This is driving me mad! Could my PRV be faulty and only allowing a max of 30 l/m. Where's my other 10 l/m going??

 

[hazetimesfive]

flow rate decreases through fittings?

 

[dilalio]

There is also a change in what you will be getting at your main, depending on the time of day!
Doing tests at peak demand is highly likely to give different results from tests done during off peak periods - worth bearing in mind as I'm pretty sure you'll be standing under your shower(s) during these peak times!

 

[fezster]

I'm more trying to understand why individually the bath (and I'm assuming probably equally the shower) is capable of delivering 15 l/m from hot and 15 l/m from cold, yet when combined, it only delivers 20 l/m.

Yes it could be pipework and fittings, but 22mm should be sufficient for flow well in excess of 20 l/m. According to this calculator:

http://www.tlv.com/global/UK/calculator/water-flow-rate-through-orifice.html

At 2.5 bar/2 bar, even 15mm can deliver 74 l/m. And 18mm (probably closer to my internal diameter for polyplumb) can deliver 104 l/m.

 

[fezster]

At the risk of talking to myself here.

I found a drain off point just before the megaflo cylinder, which is on the cold water intake to the cylinder, to which I attached my pressure gauge. My stop cock is approx 3m to the right in the pitcure and the following components are fitted after the stopcock:

Stop Cock ->
22mm pipe to outside tap/kitchen sink ->
Water softener (high flow pipes. Tried bypassing, flow rate is unaffected) ->
Cold water isolation valve ->
3 bar Megaflo Pressure Reducing Valve ->
Balanced Cold ->
8 bar PRV ->
Speedfit reducing tee to ~3m of 15mm pipe to outside tap (shown in pic) ->
Drain off point (you can see the pressure gauge fitted)

This is reading as 2.6 bar. Sorry for the unclear pic below.

First question - is the gauge showing only 2.6 bar any cause for concern? Is it probably just inaccurate, or the Pressure Reducing Valve not able to produce 3 bar exactly, and perfectly normal?

Second more pertinent question. The 15mm outside tap after the Pressure Reducing Valve has less than half the flow rate (18 litres/min) compared to the 22mm (reducing to 15) outside tap which is connected before the Pressure Reducing Valve (has a flow of 40 litres/min). Can this be explained by the 15mm pipework? Could it be one of the other components inbetween causing this reduction in flow rate? Could it be a malfunctioning Pressure Reducing Valve causing a reduction in flow rate?

I'm tempted to just replace the Pressure Reducing Valve with the same model, but before I appoint a plumber and spend probably close to £120 doing this, I'd like to know if it's even a remote possibility.