Shower flow rate help

Discussion in 'Plumbers' Talk' started by rich2766, Oct 12, 2018.

  1. rich2766

    rich2766 New Member

    Hi there,

    I've read many posts and found a lot of help from the forums but I have a problem and I'm not sure how to overcome it...

    First of all I would like to highlight that I am very aware of the difference between pressure and flow rates. It's part of my job, but I'm not in the plumbing trade.

    Okay, I'm remodeling my house and intend to create a new walk in shower. This will be the only shower in the property

    The building of the dedicated walk in shower is going to come with a high price tag and I need the shower to have a high flow rate ... Something in the region of 20 litres per minute.

    My cold water supply runs at 12 lpm and the hot water supply through the taps and current shower runs at 8 lpm.

    Cold water = 12 litres per minute discharge rate
    Hot water = 8 litres per minute discharge rate
    Cold water supply pressure is approximately 3 Bar.

    At present there is a three year old combi boiler providing hot water.

    With the mains cold water supply of 12 lpm a boiler change will result in a flow rate that will match, but not exceed 12 lpm for obvious reasons.

    What method or system of heat generation, storage tank and pump will be required to achieve the flow rate I desire?

    I am happy to leave the current combination boiler in situ to provide hot water and heating for the house and prepared to install a separate dedicated hot water supply purely for the shower.

    The cost of a dedicated hot water supply is not the primary concern. If I can't achieve a flow rate greater than the current cold water flow rate (12 litres per minute) then the building of the new shower cubicle will be pointless and I'll have to go back to the drawing board.

    Any help, recommendations or advice will be greatly appreciated.
  2. kiaora

    kiaora Well-Known Member

    You want 20 l/min
    You got 12 l/min ?

    The maths.....
    How long do you want to stand under the shower?

    10 mins?
    = 200/10
    = 20 l/min
    So you need to have 200 lt of water on demand ?

    A combi can’t do that?

    So a store and a pressurisation unit required,

  3. retiredsparks

    retiredsparks Well-Known Member

    Why exactly do you need 20l/minute ?
    Is 12 not enough ?
    I suspect you will need a bigger cold water supply from outside stop tap.
    Certain shower rose configurations can make the shower spray 'feel' a lot more powerful.
  4. rich2766

    rich2766 New Member

    Hi Peter,

    Thank you for your reply.

    Yes I would expect the average shower to be in the range of 10 minutes.

    And yes, a store of readily available hot water will required.

    The volume of 200 litres is the ball park size I was expecting. Perhaps up to 300 litres so that the entire volume from a 200 litre wasn't exhausted if a shower was to take any longer than 10 minutes.

    But what exactly should I be looking at? Some sort of emersion heater with a hot water feed from the current combi boiler?

    Is there anything on the market that stands alone... ie: cold water supply to a tank which will heat the water (electric heating element?) so that the volume of hot water is available on demand?

    I'm at a loss in regards to what I am going to require to make this work.
  5. CGN

    CGN Well-Known Member

    Try having a bath instead!
    The Teach and rich2766 like this.
  6. rich2766

    rich2766 New Member

    Hi there Retiredsparks,

    I need a flow rate in the region of 20 litres per minute as the current flow rate of (hot water) 8 litres per minute is not adequate.

    I'm not sure how a larger diameter cold water supply to the stop tap will provide me with a readily available flow rate of hot water.

    If I had a cold water supply of 25-30 litres per minute then the solution would be to fit a combination boiler that would be able to heat that supply and provide me with the desired flow rate of circa 20 litres per minute of hot water.

    If such a high supply rate of cold water was available I wouldn't have posted my query, but that isn't the case. I only have a cold water supply rate 12 litres per minute.

    If everyone out there see's re-piping the current cold water supply from the domestic suppliers feed to my property as being the only solution then I'll peruse that avenue, but I thought some system of tank and heat source would provide a better solution.
  7. rich2766

    rich2766 New Member

    The bath is the easy one. Just open the taps and wait a little longer for it to fill.
  8. The Teach

    The Teach Well-Known Member

    rich2766,tbh consider getting in a proper plumbing company to specify and install a system to your requirements.

    currently we are fitting a walk in shower with 6 body jets and an overhead rain effort shower head. it can be done but youl need to splash some cash
    rich2766 likes this.
  9. kiaora

    kiaora Well-Known Member

    Looks like you really want a top specs system, give this company a call, we have fitted them in various places, and considering the performance you want, they’re not too expensive,
    The rep will sort you out,
    rich2766 likes this.

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