MegaFlo Pressure Issue - what should I expect?

[1456518Mike]

Hello,
I've read a lot on this forum, so hopefully I can start with a few facts:

I have installed a 250l indirect UV megaflo in the loft.
It is fed by 22mm copper from the 22mm stoptap under the sink.
Incoming main is 22mm Polypipe.

Pressure & Flow:
Static Pressure at outside tap off main: 2.8bar (1 bar dynamic running 20lpm - or could be 2 bar - see final paragraph as I used 2 methods to measure it and not sure whether either is accurate)
Flow at outside tap: 20 l/pm

Pressure on megaflo inlet (in loft):
Static Pressure 2bar, Dynamic Pressure 1 bar

Pressure on megaflow outlet (measured off shower mixer valves):
Static Pressure 2 bar, Dynamic Pressure 0.6bar.
Flow at shower(with no shower head attached (off shower hose) 17 lpm
Flow at shower (with hansgrohe shower head attached) 13lpm
Shower heads are standard handheld in bathroom, and a 10cm concealed fitting in en suite i.e. 30cm pipe from wall to shower head.

Shower mixer is a standard thermostatic exposed mixer (Hansgrohe) and concealed Hansgrohe ibox.

Strainer valves are clear in megaflow and also in shower heads.

Problem:
The power of the showers feels weak. With o.6 bar of dymanic pressure, is that what we should expect? It feels like about 20% better than a typical unpumped gravity system. Our old B&Q cheapo 2 bar pump was much better (I assume that delivers 2 bar dymanic pressure rather than static pressure?)

We get 20lpm flow at the main, and 17 lpm out of the showers (with no shower head) and 13lpm with shower heads on. bath tap delivers 13lpm, but doesn't feel very powerful. - is that what we should expect - is flow our problem or is it pressure?

With 22mm poly coming in from the main, is upgrading this of any real use? I got the water board to measure their pressure, but they said they could only do mine on the house (which I already knew), as the stopcock on the main didn't have a valve (or something) to enable a measurement to be taken at that point. So I don't know if they are supplying more than I get at the house.

Finally, accumulator (as an possible fix) - it worries me that this would be putting a lot of weight in the loft (in addition to a 250l megaflow). I think the accumulator would probably need to be around 500l to get good use from it, from what I've read. Also, it feels like these are a bit unproven in terms of long term life. Woudl they help given the numbers above?

I'm running out of ideas, and feel a bit dissapointed that I've spent about 3k installing the megaflow, only to end up with fairly weedy showers.

Can anyone have a look at the figures I've quoted and offer any ideas on what could be done, problems etc.

Measuring the Dynamic Pressure - we did as per below - is this OK?

Outside tap: made up pipework into a T shape, with a guage attached to the bottom of the T. The other connection was to the mains outlet, with the 3rd one left open to allow 20lpm water to pass through. This gave us the dynamic pressure - but is this a proper way to measure it? Wouldn't the direct flow of the water mostly pass by the outlet with the gauge on it (the one leading to the bottom of the T), and therefore naturally show a reduced dynamic pressure reading at that point, as there is no resistance to the outward flow, as there would be if the flow had to force it's way through a length or pipework to an open tap? Therefore, little to encourage (push/pressure) the water down the pipe with the gauge on it?
= low reading?

If this is a bad way of doing it, how should it be done? The first time I did it, I turned the kitchen tap on and measured at the outside tap (the Kitchen tap comes off the incoming main, just above the supply to the outside tap). This showed 2.8bar static and 2 bar when the kicthen tap was open. Which one is right: the 1 bar dynamic using the T pipework, or 2 bar dynamic using the method with the kitchen tap open?

Thanks

Mike

 

[holty]

wouldnt it have been cheaper to of asked for advice before you started the job. first thing i would of said, would be you need very MIN working pressure of 1.5 bar. if at ground source then that reading is inacurate if you have a 3 story house. been to two customers this week who seem to think an unvented will be the answer, with one of them. with a flow rate of 6l min with two taps running. its called knowing what your doing.

 

[1456518Mike]

I had 4 different plumbers come round, and all measured the static pressure and said, 'fine'. It's only now that I have had to do all the reading up on this, that I can see that what thye should be doing is measuring the dynamic pressure and flow rates too. None of them did, and as I'm not an expert, and they all said 'OK, no problem', surely they can't all be wrong!

I did ask them all and they all assured me it would be fine.

With the two methods I used today to measure dynamic pressure at the main on the ground floor, the dynamic pressure is either 1 bar (using a T shape pipework, or reads 2 bar with a gauge on the outside tap, and the kitchen tap running full. Is there anything I can reasonably do to recover the situation? The pipe run is to the loft, so would lose about .5 bar

Mike

 

[holty]

I had 4 different plumbers come round, and all measured the static pressure and said, 'fine'.

unlucky you got 4 clowns to come around. but naughty you think it should be ok to gain free advice. then do the job yourself. think the word is what goes around comes around.

 

[picasso]

How ever you measure it there isint enough pressure, I would put a break tank and pump for the cylinder, if you have one bathroom a 50 gallon tank and a 2 or 3 bar single pump will give good results.

 

[mysteryman]

Try a different shower rose. Yours is restricting the flow, perhaps because it is intended for an electric shower. Also, check that the cold feed to the shower is taken from the balanced pressure cold outlet on the unvented safety kit.

 

[Agile]

I had 4 different plumbers come round, and all measured the static pressure and said, 'fine'.

It's only now that I have had to do all the reading up on this, that I can see that what thye should be doing is measuring the dynamic pressure and flow rates too. None of them did, and as I'm not an expert, and they all said 'OK, no problem', surely they can't all be wrong!
I did ask them all and they all assured me it would be fine.

Mike

An average plumber often does not understand pressure and flow!

Furthermore they are all short of work and will be reluctant to tell you it will not work.

But I am surprised that you openly admit that you wasted four hours of plumbers time giving you free advice for you to DIY.

I am pleased its gone wrong and you have wasted so much money because you are too mean to actually pay anyone!

All you needed to do was to call a competent person to advise you and pay him about £84 for his time.

 

[1456518Mike]

Just to clarify - I didn't do it myself!! I won't risk messing around with a pressurised system (I don;t want to kill myself!)

It was installed by one of the plumbers who quoted - when each of the 4 called to quote, they tested the static pressure. The total job cost £9k for labour only, plus parts extra (which also included total rip out of a bathroom and ensuite and cloakroom, plasterboard, new ply to floor, tiling with underfloor heating. Total cost of the job approached £20k, so no-one's time was wasted.

Can someone advise how the break tank works - I've heard of this, but don't really understand it. The house has 2 showers, 1 bath. 2 Adults, 2 children. Megaflow is 250l, in the loft, fed by 22mm pipe.

By the way, Hetrae Sadia state that 1.5bar dynamic pressure is the minimum pressure required at megaflow inlet. If we have 2 bar dynamic at the outside tap, should we expect 1.5 bar at the loft (5mtres up) - I think we should. What could be causing this to reduce below 1.5 bar? The pipe route has quite a few elbows on it to find it's way there - I'd estimate about 15 90 degree bends between stop cock and megaflow on 22mm copper.

 

[Rob]

Im surprised as 13lpm shower should be pretty good. Your not using a large drench head are you? A smaller head increases velocity giving the impression of more power

 

[1456518Mike]

We've tried a range of shower heads - originally a big plate sty;e (Hansgrohe raindance), now a 10cm one, and a mira hand held one in the bathroom. Slightly better, but not much.

Am I measuring dynamic pressure in the right way? I've attached a good pressure gauge to the outside tap for the static (2.6 bar today), and then turned the cold tap on in the kitchen running 20lpm (pressure drops to 2 bar).
Is that the right way to measure it?

I've then gone to the megalow and where the mains pipe goes in, just below this is a drain off fitting. I unscrewed this and attached the pressure gauge. It showed 2.1 bar static (which given .5 drop for the rise, seems spot on i.e. 2.6 bar outside ground level, 2.1 bar in the loft). I then ran the shower on full, and the pressure drops to 1.7 bar.

Is this the way to properly measure it? If so, it tells me I have:

Ground level: 2.6b static, 2 bar dynamic
Loft: 2.1 bar static, 1.7 bar dynamic

Am I measuring it correctly?

 

[snb]

from your readings it suggests that you either have a lot more than 10 elbows in the 22mm pipe or there is a valve or more fittings causing a flow restriction.

Depending on the route of the cold supply up to the loft i would recommend a 22mm or even a 28mm direct supply up to the loft and to also change your current stop cock to a 28mm to further reduce flow restrictions.

This has solved many installs i have corrected.

If you decided to go the accumulator route you need to work how much water you want at the higher pressure and then use an accumulator at least twice that size. It is possible to get whats called a mains boost set up integrated into an accumulator which would then provide you with 3 bar. Company is TWS. Hope this helps

 

[Tinitus]

What is the flow like from your other taps? try running 2 taps at once and what is the flow like then?. Are their any filters on the shower inlets, could their be a blockage in the pipe between the shower valve and the shower head, i would check all these before looking to deep.

Paul

 

[ChrisR]

Absolutely standard figures I'm afraid.
Hansgrohe fittings are quite restrictive, as they assume higher pressures, like 3 bar.
Shower heads are getting silly ( in my grumpy-old-man-sod-the-world opinion ). Raindance heads used to be great but now they're Eco friendly which means you don't get much water coming out. They incorporate air so it feels like more water than it is, but isn't the same.

Options :
1) Change the shower fittings, including the expensive Ibox. Look for other restrictive valves etc in the system (first!)
Would probably cost several hundred plus mess for an incremental improvement

2) Install Accumulator(s), perhaps 250litres, though half that would help for one shower at a time. Weight must be on a supporting wall, that's all.
Probably cost you from a few hundred to 2k.
That would give you street pressure at the inlet to your unvented cylinder's pressure reducing valve, which would drop as you deplete the accu. You get help from the accu until you've taken about haf its volume out.

3) Install a big open cistern (break tank) in the loft with a pump, and a level switch on the tank in case it runs dry.
Total with noisy on-off pump probably several hundred to £1k, or for a quiet variable speed pump add about £600 to that
Then you could maintain say 3.5 bar at the UV inlet. More than that would be reduced anyway. 2bar maintained, is enough for most and the pump's a bit cheaper.

4) find a superecowhizzy shower head that feels tolerable and put up with it.


Take your shower hose/head and put it straight on the outside tap. ( get a 3/4 to half inch adaptor for a couple of quid). Measure the pressure/flow as you do it, then you'll have a better feel for what's what.

 

[Agile]

Your original post did not mention any plumber and specifically said "I installed" so its not surprising if I read what you had written.

I cannot see anything particularly wrong with any of the pressure measurements you have made although there is no mention of the pipework or pressure loss from cylinder to shower. Its a little surprising that the installer is not apparently able to advise you about all these aspects.

As Chris says many of these European designs expect a pressure of 3 Bar and will be giving a lesser performance with perhaps little more than 1 Bar at the shower inlet.

There are several possible remedial solutions but in many ways the Grunfoss booster set is the best. This must be fitted at ground level and fills an open tank at the best open pipe flow rate and then uses a pump to pressurise the house supply to about 3.5 Bar. They incorporate a small accumulator so the pump is off when there is no flow. But they are the size of a fridge freezer and cost about £1k

Tony Glazier

 

[1456518Mike]

Thanks for some useful tips, whihc I'll think through.

I'm leaning towards an accumulator in the ground floor utility, whihc is about 3 metres awat from the incoming main. This can then reconnect back to the already installed 22mm copper feeding up to the megaflow in the loft. This would give me incoming maisn static pressure at it's peak level during the Acc charging period (which) may reach a touch over 3 bar overnight, and will maintain this on a gradually depleting pressure basis for about 50% of volume. I might be able to fit in a 250ltr tank in there, giving about a 10 min shower, assuming about 12lpm outflow from the shower. If I want to go bigger, I'd have to put it in the loft (there's plenty of room), making sure a supporting wall underneath the beams is supportig it. I could then consider going large, with a 500 ltr, meaning it would feed 2 showers simultaneously.

After gravity loss, I think I would see the 3 bar static at the main end up as 2.5 bar static at the megaflow, which would convert to 2.5 bar dynamic when water is drawn off, for the length of time the Acc can supply, whihc with a 500lt, would be the first 200-250lts. - enough for two good showers.

The incoming flow to the Acc would be around 22lpm, so this would refill in 25 minutes, and then be available for use again, whihc doesn't seem too long.

Are any of my assumptions above off track do you think?

ALTERNATIVE:
With 1.7 bar and 17lts of flow (without the shower head attached), am I ever going to get a strong shower by fiddling around with shower heads and the shower valve? I'm looking for what out old 2 bar pump ysed to delivery, which was a strong (powerful) flow of water, and volume.

One option I had in mind was to remove the NRVs from the shower mixers as these may be reducing the feeling of a powerful shower. It's balanced pressure on Hot & Cold, so I can't see why a NRV on the mixer is needed, as neither source is stronger than the other to push water back the wrong way. Any thoughts on that? It's preferable to give that a go rather than take out the mixer and i'box, which combined probably cost about £700, and even if I did, would the new ones really make it much better?

So. the questions are:

1. Does my Accumulator thinking above make sense
2. Is it worth taking out the NRVs in the shower mixers, and what problems could this cause (if any) keeping in ind this is balanced pressure coming into the mixer.
3. If we want an Accumulator, where would be a good place to source this? And is it the sort of job that any good plumber can do, or does it require any specialist accumulator knowledge or skill. Also, as it is feeding an unvented (but not installing an unvented, as that's already done), would it need a G3 cert to work on the incoming main, that runs to an unvented?

Someone asked, can't the plumber advise on all this - I'm sure he could, but I don't want to come to him with a load of garbage I haven't thought throught or don't understand. It would be great to set out what I want to happen and why, and then get his views - which is why I'm finding this advice really helpful.

Break tank with a pump is interesting, but I think a pumpo could be noisy in the loft (only space we'd have for a big wide tank), and then if used a lot, pumpo may wear out, and costs money to run. So Accumulator (with no power required and silent) feels like a better overall bet right now, albeit they all have a few pros and cons.

Mike