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Unvented plumbing - water pressure

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  • 25-02-2014 2:49pm
    #1
    Damianpf
    Registered Users Posts: 6 ✭


    Hello

    Hoping a plumbing expert can give me some guidance.

    We bought our house last year, the plumbing was fully re-done around 7-8 years ago. It uses an unvented hot water cylinder plumbed directly from the mains - so no cold water tank and no pumps on the system.

    This mostly works OK, but because water pressure/flow varies a lot during the day in our area (Rathfarnham), we have times when pressure is quite poor to the bathroom taps. Also means we have absolutely no water when the council cuts off mains supply every now and again...

    I'm wondering firstly if this set-up is in breach of Council rules? - I haven't been able to get a definitive answer to this online and I don't want to ask them directly!

    I'm also trying to figure out how the system could be improved if we decided to do so. The attic is converted but there is still some space in the roof area. Possible approach would be to take a feed from where the mains supply comes into the hot press up to a tank in the attic, and then a pumped feed from the tank back to where the mains currently enters the hot water cylinder.

    Can anyone tell me if this solution makes sense? If so, I had some more specific questions:

    1. Is there a method for figuring out required cold water tank size? - it's a fairly big house, four bathrooms over three levels, the biggest volume demand would come from bath/showers. I think washing machine/dish washer are fed off the mains before it gets to the hot press.

    2. Are there pumps available that go up in the attic with the tank? - would be less noisy than having it in the hot press.

    3. Could the plumbing to and from the attic use flexible pipe or would it need to be copper? - flexible would make for easier installation I think. Cold water only, but under mains and pumped pressure.

    4. What sort of electrical load would the pump have? i.e. would it need a dedicated supply from the fuse board or could it operate from a socket?

    Thanks in advance for any advice you can offer.

    Damian


Comments

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    #2
    antoinolachtnai
    Registered Users Posts: 9,773 ✭✭✭antoinolachtnai


    You are correct in your suspicion that this system is contrary to the water bye-laws in Dublin. The particular problem is that rathfarnam is on a bit of a hill, so the pressure might not be great.

    The broad approach you suggest is workable. The practical problem might be that the pump will make a good bit of noise. The pump is not cheap either.

    Another possibility would be to have the water tank and not pressurise the whole system. You really need a plumber's on-site advice on this.

    The water tank and pump need not be in the attic. They could be installed somewhere at ground level. Where you have pressurised hot water, I would not do the work myself. It really needs a plumber. He will be able to do the sizing, etc no problem and make sure the whole thing is safe.


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    #3
    murphaph
    Registered Users Posts: 19,018 ✭✭✭✭murphaph


    So combi-boilers that aren't pump fed from a tank are illegal in Dublin?


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    #4
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    murphaph wrote: »
    So combi-boilers that aren't pump fed from a tank are illegal in Dublin?

    Correct


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    #5
    murphaph
    Registered Users Posts: 19,018 ✭✭✭✭murphaph


    Interesting...all those apartments built in recent years have tanks?


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    #6
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    murphaph wrote: »
    Interesting...all those apartments built in recent years have tanks?

    Some do, some don't, it seems nobody cares rightly or wrongly.


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    #7
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    I can't see why you wouldn't only want it installed via a tank in Ireland. Mains is so poor & fluctuating too frequently to be dependent.
    Even for apartments with limited space, closet tanks are available with a footprint of approx 300mm2.

    The only thing you must consider is the soon to be had water charges. In the UK, if you have an unvented hot water system, you must have a meter installed, where if you are vented you have the option of a meter or a fixed annual charge.


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