Power Shower to Mixer - How to ensure same/better performance?

[jcwacky]

I am considering having my vented hot water cylinder upgraded to an unvented cylinder. Therefore, I will also need to have our power shower replaced with a mixer shower.

However, I only wish to do this if the shower performance is going to be the same or better.

How do I ensure this will be the case?

I have read that mixer showers are less powerful than power showers, but surely this depends?

Some details:

• Water pressure measured at outside tap: 5 bar
• Flow rate measured at outside tap: 33 L/min
• Flow rate measured from power shower (head attached): 10 L/min
• Flow rate measured from power shower (no head): 26 L/min
• How built in 1997
• Shower room on 1st floor
• Existing power shower: NewTeam 201-T
• Planned unvented cylinder: Heatrae Sadia PremierPlus 210L

 

[Madrab]

What is the current power shower/shower pump?

 

[jcwacky]

It's a NewTeam (Showerforce) 201-T and has the pump built in.

 

[muggles]

Personally I'd take a Joule Cyclone over a Heatrae Premier

You should get out what you put in, and as your mains performance appears to be better than your current shower performance, I'd expect a mixer to show the improvement you're after, provided of course it is chosen carefully as some are more restrictive than others

 

[jcwacky]

Personally I'd take a Joule Cyclone over a Heatrae Premier

Ah ok. Not come across a Joule Cyclone before. Why do you recommend it over the Heatrae Premier?

You should get out what you put in, and as your mains performance appears to be better than your current shower performance, I'd expect a mixer to show the improvement you're after, provided of course it is chosen carefully as some are more restrictive than others

Thanks, that's reassuring. I'm finding some brands of shower are very open about flow rates at different pressures (Bristan), but others not so.

 

[Madrab]

Not always, mains dependent then they can be as good or better, as @muggles mentions, especially coupled with a good cylinder. Pick a shower and head that is designed for a low pressure system, it will have the least restrictive waterways and thermostat, maximising delivery.

Is your pressure measured as dynamic?

 

[jcwacky]

Not always, mains dependent then they can be as good or better, as @muggles mentions, especially coupled with a good cylinder. Pick a shower and head that is designed for a low pressure system, it will have the least restrictive waterways and thermostat, maximising delivery.

Is your pressure measured as dynamic?

Good tips, thanks.

My pressure measurement was static.

 

[Madrab]

Fit the gauge to the outside tap and open one or two taps within the house and see how the pressure behaves.

 

[jcwacky]

Fit the gauge to the outside tap and open one or two taps within the house and see how the pressure behaves.

Just took some more measurements:

Outside, static: 4.2 bar
Outside, dynamic, with cold water tank filling: 4.0 bar
Outside, dynamic, with kitchen tap on (~16L/min): 4.0 bar
Outside, dynamic, with kitchen tap on and cold water tank filling: 3.6 bar

 

[Madrab]

Should be more than adequate a supply as those reading go. Your Unvented supply pressure will need to be reduced down to 3bar into the cylinder by the PRV on the control group but that should be more than enough. Just have the cylinder supply and shower feed pipes @22mm if you can to maximise flow and minimise noise.

 

[jcwacky]

Thanks. From what I can tell, the pipes that head off to the shower are 28mm, but the mains supply in the house is only 15mm. Is this likely to significantly affect things?

Looks like it's about 10 meters of 15mm pipe from the stopcock to cylinder location, with about 6 elbow joints.

 

[Madrab]

It would limit the flow as it obviously can't flow the same volume of water as a 22mm pipe could. That being said it can supply enough for an unvented system as long as it meets the manufacturers minimums. If you could though, consider upgrading to 22mm.

 

[jcwacky]

Thanks. Replacing the 15mm with 22mm would probably require signaficant work in our ensuite and bathroom, so unlikely to do that ATM. Presume putting it up the outside of the house is a silly idea??

Is it worth attempting to take some pressure and flow rate measurements from the supply into the cold water tank, to get a more accurate idea of what the cylinder supply will be like?

 

[jcwacky]

Ok, I've managed to take some measurements from the 15mm pipe currently feeding my cold water tank in the loft, that will end up feeding the new unvented cylinder:

Static pressure: 3.8 bar
Dynamic pressure (with kitchen tap on): 3.5 bar
Flow rate: ~27 L/min
Flow rate (with kitchen tap on): ~25 L/min
(During this time the static pressure at outside tap was 4.4 bar, kitchen tap flow rate is 13 L/min)

Planning to get a Mira Atom EV shower with a Heatrae Sadia PremierPlus 210L unvented cylinder.

How are these numbers looking?

 

[Madrab]

OK, seems that you have a supply that will run an unvented, you only get out what you put in though so that needs to be kept in mind.

Make sure your installer has his unvented quallies.