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New boiler and low flow rate

Discussion in 'Plumbing and Central Heating' started by Samo270, 16 Nov 2020.

  1. Samo270

    Samo270

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    Hi everyone, I've just moved house and one of the first things I am considering updating is the boiler. The current system is a Potterton Performa 28i combi which is pretty old although seems to be working reasonably well so far.

    I have been doing a bit of research looking at the different systems - condensing combi, vented system and unvented systems and wondered what advice people had. I am aware the cheapest and easiest solution would be to swap out the existing combi for a more efficient condensing combi. However, the reason I have been considering different systems is that we are considering adding a second bathroom to the property in the near future and I have read that combis are not great at running say two showers at the same time. Therefore for future proofing I would be willing to spend more to put in a system that could cope with the additional bathroom. Space is not really an issue so I could accommodate a cylinder if needs be and water tank in loft.

    In addition to this I don't think the water flow is that great at my property. I tested it the other day (in upstairs bathroom) and only got 8l/m. I plan to test this on the outside tap at some point. I also plan to get a water pressure gauge to test this. This got me wondering what the size of the mains supply pipe is (haven't figured this out yet). At the stopcock i can see 15mm going in and 15mm going out (which seems small to me) but I can't see much of these pipes beyond whats at the stopcock.

    So I guess questions I would like to ask is:
    Has anyone else had a similar situation and what type of system did you opt for in the end? What system is best for low flow rate?
    What type of things can I do to further investigate flow rate and could an increased supply pipe make much difference to flow and help me choose what system to go with?

    All help is much appreciated. Thanks.
     
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  3. muggles

    muggles

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    The first thing you need to do is get a definitive answer on what your mains pressure and flow rate are. If you've got high static pressure but low flow rate, that potentially gives you more options than low pressure and flow. LP/LF will usually point to loft tank storage and a vented system, with pumps if you want to make it high pressure.
     
  4. Samo270

    Samo270

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    Thanks muggles. I've got a water pressure test guage on order so will measure this when it arrives along with the flow rate.
     
  5. dilalio

    dilalio

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    Best to measure at an outside tap or washing machine valve as kitchen sink taps mostly use small bore flexi hoses these days and are therefore restricted.
     
  6. Samo270

    Samo270

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    Will do dilalio. I've got an outside tap in the garage so will test it here to begin with.
     
  7. dilalio

    dilalio

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    Would defo look at prices for getting a new main in. You could ask your water supplier to come and do a flow/pressure test at their stopcock... Most seem happy to do this, just say you're concerned there's an issue with it.
     
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  9. Samo270

    Samo270

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    I am definitely considering this. I want to put a new driveway in so would make sense to put a new main in before I do this. That's assuming my main runs under the driveway.
     
  10. Madrab

    Madrab

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    You want to do 2 tests, one with a pressure reading at the outside tap reading (static pressure) and then the flow rate and then with more than one tap (dynamic) when you are doing your tests.

    If you are looking at unvented then you are looking for at least 2 bar @ 20L/Min dynamic. If not then there are, as you have mentioned, other solutions.
     
  11. Samo270

    Samo270

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    So I've got my pressure guage this evening and measured the static and dynamic pressures at outside tap. Static I am getting about 2.5 bar and dynamic with running kitchen tap I am getting about 1.5 bar.
    I measured static flow rate the other day and got around 12 L/min from the outside tap. Should I be measuring dynamic flow rate as well?
     
  12. sxturbo

    sxturbo

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    Yes measure dynamic flow aswell.
     
  13. Madrab

    Madrab

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    @ 1.5 bar dynamic then your flow shouldn't drop by that much as 1.5 bar is still enough pressure to deliver that amount of flow.

    At those flow levels then I'm afraid I wouldn't recommend going to the expense and upheaval that installing an unvented cylinder would create. Time to call your water transporter and ask them to do a mains test and see what they come up with to see if an upgrade to the mains would be of benefit.
     
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