How a Direct or Indirect Unvented Hot Water Cylinder Works 2024 BBC Rogue Traders Expert Ian Puddick

We receive calls to our office all the time asking us to quote for a Megaflo (correctly called a Unvented Cylinder) as customers believe an unvented cylinder will INCREASE water pressure and flow rate.
BE WARNED - THIS IS NOT ALWAYS QUITE TRUE
This video explains the benefits of an unvented cylinder but importantly it explains the criteria you MUST you require in order for the unvented cylinder to work appropriately.
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UPDATE MAY 2021
I get emails every week from all over the UK from members of the Public whom have consulted their own plumber who says my information in the video is wrong, in addition there are now Pumps specially designed to be installed on the incoming* water main (*this true)
Am I wrong, No, here's why - (Ps, I really really don't mind being wrong & admitting it)
My Reply
You cannot install a pump on the incoming water main pipe as it breaches Water Regulations, that said, there are several pumps designed to be installed on a water main. IMPORTANT BIT read the small print, Iv'e copied here
'This Salamander intelligent pump functions at 1.6 bar closed head; it will typically boost pressure by up to 1.5 bar while regulating* flow up to 12 litres/min to ensure it complies with water fitting regulations.'
*regulating - the pump intelligently ensures the Water Flow Rate will NOT exceed 12 Litres per min
A customer thinks 1.5bar ...fab, il get one, my plumber said it will increase the flow and its legally designed to be installed on the water main (which is true) ...... the pressure is NOT the issue, its the flow rate that's vital and the max flow by law a water mains pump can increase the flow rate too is 12 litres per min. YOU NEED A MIN OF 20 Litres Per Min for an unvented to fully function.
Hope this makes sense. Forgive me I'm really not trying to be smarty pants, but 2 people so far (one in Slough and one in Notting Hill) have installed Unvented Cylinders + Pump and have a max flow rate on 12 litres per min, yes they can have 1 good shower however as soon as someone flushes the wc, puts on the W/Machine or D/Washer or fills a kettle, the shower is affected.
The (min) of 20 Litres per minute is VITAL
Hope this helps
Ian
0208 829 8244