Do megaflows etc really work OK on less than 20litres min ?

[mrsdecisionmaker]

I have enjoyed reading your forums on benefits of pressurised water for washing (Megaflows etc) - summarised as no tanks in loft,no need for shower pumps,more hot water for family of 5 to use.

Great ! so quite keen to commission a system as we want to convert a loft and add an extension which includes 2 bathrooms BUT our mains pressure inside is 2bar 13l /min. All the advice seems be be flow rate is key but water companies do not guarantee more than 1 bar 9 litres a minute. And yet these systems 'require' 20l/minute 2 bar.

How can I or other people go for a pressurised system when it will be subject to the vagaries of water pressure from outside home and even expensive ( £600-£800) new pipes from external stopcock can only pass on slightly improved flow rates ? And the systems are more expensive.

Or do these systems actually often work OK at lower flow rates. How come they are popular?

Both the water company technician and water supply pipe contractor were not convinced on pressurised systems (even tho the pipe contractor was doing himself out of a job). Our plumber is a bit nervous of the water supply although at customer insistence he has installed one on the same road which occupants seem to be happy with.

Our alternative is upgrade of what we have (keep cold water tank in loft) plus pumps for showers and probably electric shower and electric hot water hand washer unit in loft.

Trying to make a decision so any advice welcome.

 

[Agile]

If you have quoted an open pipe flow then you will get about 5-7 li/min in total out of all your hot taps.

If you dont want to upgrade the mains pipe then you can install a Grunfoss pump set at about £900 plus installation. It will take up space, make some noise and need to be repaired/serviced.

Or you could upgrade your mains supply ( for less ) have no maintenance costs or take up any space!

Unventeds are popular with those who find spending £2k-£4k worthwhile to get good HW performance.

Your qualified plumber should be able to advise you about all this! Or is he a nupty?

Tony

 

[mrsdecisionmaker]

Yes would really like this apparently simple (tho expensive solution) ie we can pay for new pipe in our garden but concern is the flow rate is not 20 litres/ minute, especially in early morning 8amish when everyone else is bathing, in summers when water is scarce etc.

So we could go to all this expense and not get a result, so what is the experience of minimum flow rates and good megaflow( or other) performance ?

Plus various ad hoc comments - for example if we were to request 32 mm at water company stopcock they would regard this as new supply -so onto a water meter which water company technician said would drop flow by 5 litres/minute or so.

 

[Agile]

If anyone were stupid enough to answer you then this would be just THEIR opinion.

We reply as professionals based on the recommendations for certain equipment. On an unvented thats a dynamic flow rate of at least 22 li/min/1 Bar for good performance.

An open pipe flow rate of 22 li/min will give about 10-12 li/min through an unvented and this is way below what anyone spending over £1400 would ever want but I would give a written disclaimer to any customer wanting me to fit one.

If it makes you happy, I went to an architect who had a combi which gave about 4-5 li/min open pipe and he had not realised that was grossly below par.

He did notice the combi boiler was cutting out on overheat though!

Tony

 

[mrsdecisionmaker]

Yes, I am trying to understand why megaflow type systems are so popular when in some areas water flow and pressure are know to be ''poor'' - ie less than 20litres/ 1 bar.

So a professional company could not recommend them completely as water flow/pressure rates are outside manufacturers recommended range. But if no water company will guarantee flow or pressure rates above 9 litres/minute 1 bar then how can anyone anywhere put them in?

Eg if there were a dry dry summer and the water companies are forced to conserve stocks via flow reduction then surely all these expensive systems will just slow down?.

 

[Agile]

We test each address as the flow rate depends on the pipe into each property.

Each one is individual and most people update the supply pipe if theirs is below par.

I am installing a combi where the open pipe flow is 47 li/min all from a 15 mm supply in an upstairs flat.

Water Cos dont usually reduce pressure to conserve stocks under normal conditions.

Tony

 

[mrsdecisionmaker]

But upgrading pipework won't necessarily improve much if the water main is at 2 bar and 18l/minute. So are these high pressure systems really able to work at lower flow rates ? Or why aren't there more unhappy megaflow ( and other) customers etc. Many thanks

 

[mrsdecisionmaker]

Just spoken to Megaflow helpline technician and he says need 1.5 bar working pressure and 20l/ min for effective use. If haven't got that then to help with pressure and flow can look at getting a cold water storage tank ! ( but the aim is to get rid of it!), and a grundfos home booster system (£940ish). Digging up garden, now extra pumps, plus maybe upgrading pipes internally, all to make an expensive system work. Is it worth it ?

 

[gas4you]

Search on here for accumulator

 

[wetshoes]

Do the people in your road that had a megaflow installed have the same supply pressure & flow as you do?
Take a shower round at their place while running their bath & kitchen taps to see what it's like.

 

[mrsdecisionmaker]

Yes I think their pressure and flow will be similar - about 100ft away on same main - and they may not all shower at the same time and use the kitchen simultaneously so it may not matter, but I will investigate !

But my point is why go to all the expense of these unvented systems and then find that actually it is all compromised by poor flow and pressure, eg at peak times 8am when no one comes out to measure flow or pressure? (They're at home having their own shower!).

Found Dualstream products in searching accumulator. But why bother with all that when you can buy pumps ? I am after good showers probably like most people ? So is an unvented system with pumps the all round winner?

 

[electronicsuk]

But my point is why go to all the expense of these unvented systems and then find that actually it is all compromised by poor flow and pressure, eg at peak times 8am when no one comes out to measure flow or pressure? (They're at home having their own shower!).

Who are these unknown people you are referring to? Only the misinformed would install an unvented cylinder on a water supply with poor pressure/flow rate.

Presumably those that are disappointed with the performance of their unvented cylinder are those that employ a numpty installer who has not bothered to check the suitability of the supply first. Once they have parted with their money, there is little legal recourse without taking it to court, which is again more expense.

Found Dualstream products in searching accumulator. But why bother with all that when you can buy pumps ? I am after good showers probably like most people ? So is an unvented system with pumps the all round winner?

Why bother with a pumped unvented system? A pumped vented system with CWS tank will be far cheaper to install and run, and requires no specialist maintenance. This would be my choice.

 

[Agile]

You seem to be very concerned with the cost.

You have to understand that an unvented is for those people who want the best showering experience and are prepared to PAY for it !

Thats usually £2000-£4000.

In this life you generally get what you pay for!

Tony

 

[Axel]

Unvented cylinder cost: £ 600

How many days labour to fit one?

(G3 course costs £180)

Yes in some situations there could be a lot of work, but usually there's just a few extra pipes to be run and the whole thing would take a long day, on average.

So in many installations, it should be possible to do it for not too much more than 1k, unless your plumber is charging £ 150 per hour.

 

[Norcon]

Agile Wrote

An open pipe flow rate of 22 li/min will give about 10-12 li/min through an unvented and this is way below what anyone spending over £1400 would ever want but I would give a written disclaimer to any customer wanting me to fit one.

Are you saying that a mains pipe is delivering 32/L min between two outlets but because someone has left the garden tap on then the shower is only 10-12 ltrs?

And then you write a disclaimer?

EDIT
If its total flow I doubt you will get a loss of 8L/min. It will be subject to the pressure available. If gravity flow maybe.