Megaflo system - inadequate flow rate

[lxbn]

Because I'm planning to have a loft conversion, I thought it would be a good time to consider having a dry loft and installing a Megaflo system - the Heatrae Sadia Megaflo to be installed in place of the the hot water cylinder in the airing cupboard on the 1st floor. I currently have 1 bath/shower room and 1 shower room with another shower to be installed in the loft when it gets done.
The plumber came out and tested the flow rate and said that at 12 ltr/p min the flow rate was not enough for a Megaflo (their min is 20 ltr/p min) and I had 2 options a) replace the mains coming into the property with a bigger pipe at a cost of some £2500 plus with no guarantee that the water company will continue to provide a good flow rate or b) have an accumulator installed which is a tank about 1.2m high and 0.5m diameter for an extra £1000 that will boost the flow rate to about 26 ltr/p min. Not too happy with having yet another tank taking up space and using a technology I had not heard of before, I spoke with the technical person at Heatrae Sadia who advised against the accumulator (wasn't convinced about it) and suggested instead that I leave the cold tank in the loft and install a pressure switch motor on the supply pipe out of the cold tank to boost the rate into the Megaflo.
Now I'm not sure what I should do and not knowing much of Megaflo systems before this, can't decide on the advice, opinions and options I've been given as the choices are so different. I'd be grateful for information if anyone has had any experience with Megaflo systems.

 

[gas4you]

Your plumber is correct in that at present you would be wasting your money with the megaflo.

As he says you ideally need 20 l/min but also a minimum of 3 bar incoming mains pressure.

You will also need a 22mm cold supply from your internal stop cock to the megaflo.

have you asked your water company what the pressure is in your street?

I do not know anything about accumilators (including their spelling) so cannot offer advice on these.

Hopefully Simon D will come on later as his company has fitted loads and he can advise from experience.

Can't understand why Heatrea advised against this though

 

[ChrisR]

You do need to measure your mains pressure, though as above there are no guarantees.
Accumulaotrs need pressure too.
An acc that size would soon deplete if you use a bath and shower together.
I'd risk the mains staying at reasonable pressure , say if it's 2.5 bar or above, depending on what your water co and plumber advise. If you don't want to do that then I'd go for the pump, which can give you 3-4 bar or whatever.
Megaflo isn't everybody's 1st choice of unvented - see previous posts.

 

[lxbn]

I'll have to check with Thames Water about the pressure at the mains supply - they have already told me that by law they are obliged to supply a flow rate at a min of 9 ltrs/p min, so at 12 lts/p min I'm above that!

As I'm completely new to the idea of megaflo systems, I latched on to Heatrea Sadia as the foremost supplier of these type of systems. I have seen other posts here about the Heatrae Sadia system and concerns of build quality/pressure bubble worries(!) with it being bought out by Baxi etc. There is also a raging debate about the accumulator as well. I'm only a lowly user, so without upsetting anyone and only wishing to be reliably informed, is there an element of vested interest involved in these debates - these issues seem to be so contentious.

 

[simond]

As I've said more than a few times before, an accumulator will help in these situations.

We are not allowed to fit an accumulator from our preferred suppliers to a new Megaflo, due to some underhand (but unsuccessful) efforts by Megaflo's owners to undermine some intellectual property. The 26 l/m figure is pure fiction from the Baxi helpdesk*, in principle almost any flow rate can be designed for, with the limitations being from pipe sizing and the valvework associated with the cylinder. I see around 70l/m through my system at home, although this reduces as water is drawn off.

*If you are looking for fiction this is an excellent place to start.

The good news is that this is almost certainly the solution you need, and companies with confidence and experience in the technology will underwrite their designed solution on a 'no fee if it doesn't deliver' basis.

The bad news is that the licensed supplier of accumulators in the UK has just announced a 45% price rise. Incredible but true.

 

[chrishutt]

is there an element of vested interest involved in these debates - these issues seem to be so contentious.

You bet! apart from the manufacturers themselves there are installers who specialise in unvented cylinders and, in at least one well known case, accumulators. Those rest of us tend to be rather sceptical of claims made by those vested interests, especially about accumulators. If you're really interested there's a very long thread here.

 

[simond]

Chris

Those rest of us tend to be rather sceptical of claims made by those vested interests

This forum has significantly driven up the number of accumulator installs my company are doing. To all those sceptics, keep up the good work.

I do think it would be useful to their cause if the sceptics could find some evidence of a real customer who has had an accumulator installation, where they are dissatisfied.

I am personally aware of a couple of instances where the system was specified or installed incorrectly, only because we were called in to rectify. In one case there is a court case pending against an installer who made a fundamental error but refuses to admit liability or give a refund to the customer.

 

[chrishutt]

Simon, I've never doubted that accumulators do what they do. But I would always consider upgrading the main supply as the preferred option. Once done, the pressure/flow problem is resolved permanently (well, as permanently as anything given the impending environmental catastrophe of global warming), without having to find space for a bulky bit of kit and usually at much lower cost.

If I did need to go down the accumulator route I would be purchasing a pressure/surge vessel for a fraction of the price of the accumulators you supply and fit.

 

[simond]

Chris

I agree with you in so far that we would source our own vessels, if price was the only consideration.

But I have no intention of leading my company or our customers into a potential legal minefield, so we use the only product which is permitted by a UK patent for the purpose. The UK licensee has also put them through WRAS approval.

We can source the same units from the US - where they are used for borehole pumped systems - for less than half the price, this is not news to us.

We will leave it to someone with deeper pockets and possibly a misguided appreciation of patent law to test the market....

 

[davecon1]

Hi there

I had my loft converted a couple of years ago and was advised that a megaflo would be the best alternative for me. Mine is also in a cupboard in the second bedroom as it directly replaced the old system.

As both my neighbours had loft conversions and swore by their megaflos I decided to invest in one. Unfortunately I didn't do quite a much research as you and trusted the advice of the plumbers that quoted for the system. It turned out that my pressure is 2.7 bar and flow rate is around 17 l/m which is not ideal but passable.

Saying that it made a huge difference from the old system in terms of a power shower but the problem comes when you run 2 showers at the same time. I hopeful this can be resolved as I'm running new 22mm pipework up to the megaflo which will balance the system and improve the flow rate.

My original post caused one of the biggest debates on this forum it still seems to be going. I looked into an accumulator but decided against it as it would need to be huge to work effectively. It's also really expensive!

I can't really advise you what to do but if I were doing it all again I'd probably just stick with a conventional system with a cold water coffin tank in the loft (in the eaves) and a nice big pump hidden where you won't hear it.

Hope this helps.

 

[sooey]

I can't really advise you what to do but if I were doing it all again I'd probably just stick with a conventional system with a cold water coffin tank in the loft (in the eaves) and a nice big pump hidden where you won't hear it.

Bottom of the garden, about six foot down.

 

[lxbn]

davecon1 you were braver than I and took the step of installing the system, albeit with flow problems when using more than one shower. I really wanted a dry loft and now that my council has granted permission for the loft conversion I must act quickly, but still in a fix about the megaflow. My pressure was measured at 1.5 bar and flow rate now at 16ltr/pmin (mains feed from outside is lead, changed to 22mm in the house but the pipe to the outlet tap at which the measurement was taken is 15mm). and 2 installers in the past week have assured me that these conditions were adequate for a megaflow - guaranteed, as each of them had already installed several that had even lower flow rates than I have and the results were good. So it's interesting that you have found that it didn't work so well even with your higher rates. I spoke with Heatrea Sadia this morning and they advised me that they would not recommend the system if the flow rate was below 20ltr/pmin.
I am coming to the conclusion that if I want a megaflow system that works well, I will have to bite the bullet and have the mains pipe into the property changed at a cost of something like £2500 on one estimate and trust that it does the trick(!?). Someone told me that the water company will install a meter when they have to make their connections to the new pipe - now that really would upset me as I can see myself taking long showers if it works as well as people keep saying it does!
I hope you sort out your problem davecon1.

 

[davecon1]

I've been toying with the same decision as you about digging up the mains and going for a 22mm pipe but no one has been that brave to give a guarantee that it will make a huge difference.

The main issue for me is the flow rate which is weaker than it should be. The strange thing is that it's fine for the neighbours so I think the problem with my pipes is actually inside the house leading to the megaflo. It's only a 15mm pipe and is a real mess in terms of taps and isolators under the kitchen sink.

I'm planning to replace the kitchen and all the pipework which should in theory help with the flowrate.

Good luck with your conversion- keep us posted if digging up the mains pipe works as I might have to do the same!

 

[ChrisR]

From the systems I've seen, 1.5 bar really isn't enough for an unvented cylinder system. If you have enormous accumulators near the outlets then fine, but that's not really practical in many cases. A thermal store/heat bank has lower losses than the valvery on an unvented cylinder, but wouldn't help enormously.

A shower feels good to many people only if the water jets feel FAST. You aren't going to be excited by 1.5 bar whatever the volume flow rate is. A bucket of water over your head from just above, is a high flow rate, but might not be what you want. The only way to increase your pressure, is to use a pump. Some, eg the Salamander ones advertised as being quiet, aren't too noisy at all, if installed well.

 

[davecon1]

Hi Chris

is there any pump on the market that will work with a megaflo. I've heard they do exist but in theory should not be fitted as it's straight off the mains.