mains pressure shower

[paul_round]

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How is the shower working now for you not to be happy with it ???
It is working, but I am not happy with the performance.

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Is the pump still in line?
No, because it is now mains pressure.

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Where is it connected into the existing system?
Everything is in the loft, connections for shower are close to origin from hot tank. As I said, I am more than happy with pressure for everything else.

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Was it explained to you beforehand that the shower would not or might not work after the cylinder was fitted?
No

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What does your plumber propose to do as a way round it that costs £500?
Don't know. I have not pursued this as I am very reticent to spend another £500 just for the shower.

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Has the installation been registered with the local authority and benchmark booklet filled in?

Again, don't know, he is back on wednesday to finish off, so I can get my wife to check this.

When I said ' going through the new cylinder, into the old then back to the boiler' I meant the cylinder heating circuit only, not supply, I would keep the actual supply for the shower separate with a tank, (my reasoning behind this is that we still have the old cylinder and tank). But if this is not possible, then I guess using the immersion heater would be OK

 

[ChrisR]

Much point-missing here. An unvented cyl will supply hw at the LOWER of the pressure its regulator is set to , and the mains pressure. If the CW is connected to give balanced supply, after the regulator, the same applies.
What make is you cylinder?

Did your plumber measure the mains pressure and flow before he started? If not he's incompetent, even if he's done the course, which only means its safe.

Its very unusual to find a house where the mains would come out of a 15mm pipe, in the loft or further(pipe length wise) at 25l/min, though your figure from the pump (what's the make and model) may depend on a lot of things so hard to use it meaningfully.

SO in practice with a Megaflo (air bubble in the cyl) you get HW at a higher pressure than the CW, until the bubble is depleted then they're the same.

Your plumber may be thinking of an Accumulator - yes they're expensive, and will still only give you the lower of... as above, you just avoid pipe losses.

Yes you can reinstate your old cylinder and pump - the money spent is wasted already.

 

[paul_round]

Yes Chris, it was an accumulator!
He did check the pressure which he said was fine. As I have said, I am very happy with his work, we now have great pressure on all our taps, bath etc, I just want my power shower back.
From what has been said here, maybe I didn't get the full story, but it's too late to go back now, he has done a great job with everything else, however I have to say that the pros definitely outway the cons, the shower issue is minor in comparison and its not really a big deal for me to install the system I descibed myself, as I still have all the parts.

Not sure on the make of the water tank, (I can check this evening)
The shower pump is a wickes brass twin impellor

 

[ChrisR]

He obviously didn't check the flow.
I don't think any wickes pump will be more than a couple of bar, so your pipework must be quite restrictive if the mains IS a decent pressure (4 bar or more) and the shower is poor. Has he checked the pressure at the regulator on the cylinder?
If mains is less than about 2.5 bar or flow less than 25 litres/min at cold taps I advise against unvented cylinders for normal installations - ie a couple of showers... OR where a decent (3 bar or more) pump has been used.

 

[paul_round]

Cylinder is an Ultrastell 180L, the inlet control is set to 3bar. My figure of 25lires/minute for the pump is from the pump body itself. Also bear in mind that it was fitted to our old water system, which was gravity fed with a cold water tank.

 

[Slugbabydotcom]

These things arent just about pressure as the pressure measured is usually static. A restriction anywhere in the system can reduce the dynamic pressure as can turning on another tap so its highly unlikely that pressure is the problem. So to concentrate on the water flow rate this should be a minimum of 20 litres / min for your cylinder.
If it takes more than 27 seconds to fill a 2 gallon bucket you dont have the volume of water required or more to the point the unrestricted diameter of pipe to allow the required volume even if you do have the pressure.
When I fit an unvented cylinder the first thing I check is that an outlet can fill the bucket in the required time. [One of these days I will buy a flow meter] If I am in any doubt I inform the customer that the flow may not be up to it and the possible implications eg. the rising main and or water service may have to be renewed plus things such as showers may not work as expected. I would consider myself negligent if I didn't.

You say that everything else seems to be working fine so it points to a restriction in the pipe as stated by the Bahco's first reply in this topic

Perhaps your shower needs attention!

or a restriction elsewhere on the way to it.
Suggest you specifically check that the balanced supply leading from the bottom of the inlet control set at the bottom of page 3 here http://www.rcmgroup.co.uk/files/Ultrasteel_Instructions.pdf
to your shower [which if not fitted should be] has no restrictions in it.
I would like to point out here that a normal isolation valve inline can reduce the pipe bore to about 10mm which is inadequate so look out for that too.

I looked at pressures and flow rates on a shower pump [stuart turner showermate] with a similar output to yours and found one that gave 25l/min and it was rated at only 1.4 bar therefore your unvented supply should be better than or at least equal to what you had from the pump if it was installed properly.

Here's a little extract from your installation instructions, the fault finder from the above link

Fault:- Hot water pressure dies away at taps

Possible cause:- Poor water pressure or flow

Solution:- Check pressure and flow to property (minimum 1.5 bar-20ltr/min)
Refer customer to local water authority.

 

[paul_round]

So I talked it over with my plumbers and we agreed the best solution is to put the old cylinder and water tank, with the booster pump back in just for the shower. It suits me fine as we get good performance everywhere, I get my power shower back and it doesn't cost me any extra.

 

[ChrisR]

Let this thread be a warning to all those with inadequate knowledge when installing these cylinders.
Any "plumber" who doesn't measure the pressure and flow available, is simply incompetent.
NO WAY is
"Check pressure and flow to property (minimum 1.5 bar-20ltr/min) " enough.
Words people can find this thread with:
unvented, pressure, flow, competent, incompetent, expensive mistake !.