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Discuss Plumbing science question about meters head and bar in the Plumbing Forum area at UKPlumbersForums.co.uk.

  1. Joshua

    Joshua New Member

    First I'll give my understanding on how I think it works, haha bear with me people.

    Say if I had a simple combination system and I wanted to make sure the boiler can heat my radiators across a flat that has an area of 50m2. The height of the flat is about 10m high. Would about 1-1.5 bar suffice in pressure to pump water to all the appliances?

    My question is about meters head, I believe that bar is the amount of pressure needed to lift water perse by so much meters head (1 bar == around 10.2m head). But if I had a swimming pool that is 20m2 and 5m deep, is that 5m head? And if I have a cup that is about 8cm in diameter but 5m tall and filled with water is that also 5m head?

    Sorry about the wording of the question, it was actually really difficult to try explain what I want haha

    Also if I have gotten it completely wrong I apologise in advance, maths and science were never my strong points haha.

    Cheers to everyone who helps!
  2. Riley

    Riley S. Mod Trusted Plumber GSR Top Contributor!!

    In broad terms yes you’re right 1m =0.1bar what is it you’re trying to work out though??
  3. Joshua

    Joshua New Member

    Pretty much just that mate, thanks for the answer.
    I just wanted to know simply because I find it interesting.
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  4. snowhead

    snowhead Plumber

    An interesting fact from my school days in the 60's.

    In the Science block at the bottom of the stairwell they had a bowl of water with a tube in it extending up to the 3rd floor about 33 ft high with a funnel on top.

    No matter how much water you poured in the top it always settled to the same level, meaning the pressure acting on the water in the bowl could only support a 33ft OR 10mtr column.

    That's the Earths atmospheric pressure at work said the Physics Master.
    Never really understood it till a lot later.

    It was more fun rolling Mercury around the lab desks that worrying about a column of water. :eek::eek:
    • Funny Funny x 1
  5. johnduffell

    johnduffell Member

    Youbquestion is a bit mixed, you need to distiguish between pressure relative to atmosphere, and pressure difference across a pump.
    You would need the full 10m static head relative to atmosphere to make sure the system is full, but that wouldnt have any bearing on heating performance.
    Even with 0.1m pump head it would still circulate some water round a 10m high system, although it would likely have a very slow water velocity. You would have to size the pump according to the desired flow rate and the system resistance at that flow rate.
    Hope that helps
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  6. rpm

    rpm Trusted Plumber Top Contributor!!

    Would pipe size come into it with a pumped system?
    Or put another way do you chose the pump taking the pipe size into account.
  7. fixitflav

    fixitflav Active Member

    Yes, to find pump differential head you need to know, at the design flow, the headlosses of rads, pipework, boiler, and any filters and cleaners. Pipework loss at a given flow varies inversely as roughly the 5th power of the diameter.
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  8. chris watkins

    chris watkins Plumber

    The way I normally try to explain it is - a booster pump or in this case the pressure behind the incoming main water supply has to overcome gravity to get the water up the building to a tap or to fill the heating pipework.
    It keeps having to do this if the tap is open but with a heating system once filled with water the flow & return complete a circuit so if we start to move water around it whatever goes up, say to the top floor rads comes back down the return, it is like a seesaw working against going up but with on the way back, so all a pump (or more correctly the circulator) has to do is over come the fictional resistance of the pipework circuit, Not gravity.
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