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Discuss Water flow path through radiator in the Central Heating Forum area at

  1. MelloPeck

    MelloPeck New Member

    I have been trying unsuccessfully to find a diagram that shows the path water takes when flowing through a domestic radiator.
    Anybody got any ideas?
  2. Riley

    Riley S. Mod Trusted Plumber GSR Top Contributor!!

    Is it to highlight something or just interested?? It will also depend how it’s piped
  3. hammers4spanner

    hammers4spanner Plumber GSR

    Generally in one end and out the other,

    Hope that helps
    • Funny Funny x 6
    • Optimistic Optimistic x 1
  4. MelloPeck

    MelloPeck New Member

    Hi, I mean the direction it flows through all the channels, does it flow from top to bottom or up some channels and down others?
  5. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    nope its open in there unless its a fancy column rad

    standard rad is indented to give the rad more surface area which increase the heat capacity a bit
  6. Chuck

    Chuck Well-Known Member

    Typically it goes up the first one or two vertical channels closest to the flow inlet, which I'm assuming is at the bottom, and down the remainder.
    • Agree Agree x 1
  7. fixitflav

    fixitflav Active Member

    If it's piped like most rads, flow and return at the bottom, if the water is going up in some places it must be going down in others.
  8. Gasmk1

    Gasmk1 GSR

    uses natural convection currents. if you feel a rad as it heats up its starts getting hot at the flow end then gradually increases across the rad.
  9. Tim Watts

    Tim Watts Member

    With a normal radiator it depends on whether both connections are at the base or one top and one opposite bottom.

    Both connections at the bottom (all of mine) are slightly weird, but explainable - you tend to get convection lifting the hot water over just one side, then the top gets hot and eventually the other side gets hot in a top to bottom way until the whole thing is steady.

    Try turning a cold rad on and feel which bits heat up in which order - that's an approximation of your water flow.
    • Agree Agree x 1
  10. Rob Foster

    Rob Foster Top Contributor!!

    In the old days ..before my time the practice was to put feed on top stabbing and return lower stabbing on opposite side. Then it was discovered that convection flow allowed in and out on bottom stabbing son opposite sides, sludge builds up on bottom between in and out and results in cold spot along bottom of rad . See pics of this to determine heat flow, or point your iPad on thermal camera at a cold rad to see fir yourself
    Rob Foster aka centralheatking
  11. YorkshireDave

    YorkshireDave Plumber

    Morning Rob.
    Rads 'were' always designed as you say. AFAIK that still works and is the most efficient & effective piping arrangement.
    The change to bottom in bottom out was led by nothing more than the technical and moral depths of 'fashion' in the late 60s. It was deemed 'ugly' to have pipes on show so, being the sheep we all are, everyone copied it and we have what we have. Where I am 'allowed', I still pipe rads top in bottom out - 'she' don't like it tho :rolleyes::rolleyes::rolleyes:
    • Like Like x 1
  12. Tim Watts

    Tim Watts Member

    Annoyingly, the vertical rads I have in 3 rooms would have been easier with one pipe in the top - as would the towel rail as I'm on a drop system (solid ground floor). But the rads all required bottom inlets (verticals have a separator in the top bar halfway).

    • Useful Useful x 1
  13. Gasmk1

    Gasmk1 GSR

    top and bottom entry was originally used as nearly all systems were one pipe when two pipe systems came in the both bottom was adopted, that is what i always thought.
    • Like Like x 1
    • Agree Agree x 1
  14. Best

    Best Trusted Plumber

    Top and bottom connections also were done on the old systems that were all gravity with no circulating pump.
    Rads on gravity also work better on top to bottom connections
    • Like Like x 1
    • Agree Agree x 1
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