Plumber says I can have unvented @ 13lpm ?

[wwwebber]

ok, had a couple of things done recently on recommendation of a plumber as we wanted an unvented cylinder :-

Very old street level stop tap replaced by local water board (no charge)
Plumber then came round to replace two very old internal stop taps with a single proper full bore one

There is a 15mm feed into house.

Plumber then measured the flow rate at the kitchen tap as 13 litres per minute which he says is fine to run an unvented cylinder. Standing pressure is 3 bar and flow 1 bar.

We want to convert from vented to unvented to run a new large mixer shower and lose the loft tanks.

So can we indeed have an unvented cylinder ? any help would be appreciated thanks.

 

[Elkato531]

Flow rate is a bit low for an unvented. Pressure is ok. An unvented would work but performance would be affected if more than one outlet running at a time. Replacing incoming supply pipe with 25mm MDPE should sort it out but may be expensive.

 

[hard-work]

At 13 litres/min go for a combi. If you can keep the cold water storage tank, then feed the toilet(s) and bath cold tap from it. Then you split the water distribution in the house. The mains water supplies the water from the combi and only the kitchen tap. Divide and rule.

But something tells me that if flow the measurement was taken at the full bore stop tap you will have a higher flow. Having 22mm pipe from the stop tap to the combi will give a higher flow as there is less restriction to flow in the pipe.

 

[wwwebber]

Flow rate is a bit low for an unvented. Pressure is ok. An unvented would work but performance would be affected if more than one outlet running at a time. Replacing incoming supply pipe with 25mm MDPE should sort it out but may be expensive.

Yes I am aware that the flow will be affected if there's demand from anywhere else in the house. This will be no different from the combi in our previous house. So looking good then.

 

[wwwebber]

At 13 litres/min go for a combi. If you can keep the cold water storage tank, then feed the toilet(s) and bath cold tap from it. Then you split the water distribution in the house. The mains water supplies the water from the combi and only the kitchen tap. Divide and rule.

But something tells me that if flow the measurement was taken at the full bore stop tap you will have a higher flow. Having 22mm pipe from the stop tap to the combi will give a higher flow as there is less restriction to flow in the pipe.

Yes, considering a combi too but the objective was to feed our new shower and lose the loft tanks as we the loft is actually a room. Cheers.

 

[wwwebber]

Thank you for the responses so far.

The plumber has also given us a quick quote for a 210ltr megaflow unvented - all in for £1200. I notice that the megaflow is top of the range kit and that others can be had for much less - eg :-

Kingspan - https://www.fueltankshop.co.uk/king...re-indirect-unvented-hot-water-cylinder/p5431

Telford - https://www.directheatingsupplies.c...re-indirect-unvented-stainless-steel-cylinder

Are these decent alternatives to the Megaflow ?

I'm also going to ask him to quote for a combi as I assume that a combi can be installed for a similar price. We already have a gas system boiler in our stove so that would become redundant. There's only two of us in the house so a combi could be an alternative.

Cheers.

 

[hard-work]

At 13 litres per min, an unvented cylinder is a waste of time and money and takes up space. It will add nothing more than what a combi can deliver in hot water. I assume you have one bathroom and one shower.

 

[ianmcd]

I too would advise a combi if all you can get is 13 L/min you say you want to run a large thermostatic shower, if you mean a rainfall type with a large shower head you might be disappointing at 13 L/min depends on what your expectations are

 

[wwwebber]

At 13 litres per min, an unvented cylinder is a waste of time and money and takes up space. It will add nothing more than what a combi can deliver in hot water. I assume you have one bathroom and one shower.

We have an en-suite with basin, toilet and a mixer shower. The shower is not in use yet until we get either get an unvented cylinder or combi.

A shower room with a basin, toilet and electric shower. The electric shower will be replaced with another mixer in the future.

We are aware that both showers will not be usable at the same time.

Are you suggesting that a combi will be cheaper and more appropriate than an unvented cylinder ?. Our current boiler is rated at 100,000 btu and caters for 14 rads of various sizes. We also want to pressurise the heating circuit so we can put a rad in each loft room. Can a combi cope with this ?

 

[hard-work]

Hansgrohe Rainfall shower heads are aerate and deliverer 9 litre per min. Keep water bills down as well.

 

[wwwebber]

I too would advise a combi if all you can get is 13 L/min you say you want to run a large thermostatic shower, if you mean a rainfall type with a large shower head you might be disappointing at 13 L/min depends on what your expectations are

ok, this is our shower head :-

https://www.victorianplumbing.co.uk/belmont-traditional-8-apron-rose-shower-head-with-swivel-joint

We do like a decent shower but don't expect a monsoon - will a combi or unvented cylinder service this shower head ok ?

 

[muggles]

If you want a greater flow rate and can't upgrade your mains, there may be scope for fitting an accumulator if you have the space. This would significantly improve your mains flow rate. Failing that, you may as well have a combi

 

[bernardgreen]

This would significantly improve your mains flow rate.

Until the accumulator becomes empty.

 

[wwwebber]

Until the accumulator becomes empty.

I've previously had the accumulator debate. I don't have the space or the money so it is not an option thank you.

 

[muggles]

Combi it is then. Look at the Intergas ECO RF 36