Unvented Megaflow - Water not maintaining heat over boiler is off

Discussion in 'Plumbers' Talk' started by Elvbee, Dec 5, 2013.

  1. Elvbee

    Elvbee New Member

    I have an unvented Megaflow system and I have noticed recently that the water does not stay hot for a long time after the boiler (3 year old) has gone off. For example in the evenings it' on between 7:00pm and 9:00pm and without much water being used it's cold by midnight. Anybody know why this is happening?

    I have the Megaflow system for 2 years and I have never got it service, now planning to get it service within the next week or so, what do I expect from a service and what would be the average price of a service?

    Thank in advance.
  2. kiaora

    kiaora Well-Known Member

    What temperature is the water, before the water is used, actually measured?
    How big is the cylinder?
    How much water is used?
    That's a start!
  3. meady

    meady Member

    The fact that it hasn't been serviced shouldnt have anything to do with how well it holds heat, that's all to do with the insulation of the cylinder.
  4. Elvbee

    Elvbee New Member

    It's nothing to do with how big the tank or how the water is used
    We have had this system in now for 3 years and never had hot water issue until recently. Must be some internal issue because yesterday I used the immersion to heat the water and it's taking well over 2 hours for warm water to flow through the tank. I suspect the heating coil is not heating up the water sufficiently enough to maintain the heat. What does anybody else think causing this issue.
  5. CraigMcK

    CraigMcK Well-Known Member

    Just want to check. Are you saying neither the boiler or immersion heater is heating the tank correctly?

    If so that's two separate heating circuits, so you can almost certainly rule out the heating side of things

    Have you checked the safety valves, is there possibly water running off the tank all the time that's keeping it cool be constantly taking in cold water.

    If it's a mega flow, then it may have lost its internal bubble. Turn off the intake valve on the unit and open the pressure release valve, there should be no water coming out. If there is that's a problem. Keep it open until water stops flowing. This is shown on a label on the side of the tank

    Ps a little patience with the other replies might get you some better responses too, remember we do this for free!
  6. kiaora

    kiaora Well-Known Member

    you say in your original post... ''I have noticed recently that the water does not stay hot for a long time after the boiler (3 year old) has gone off.''
    now you say the water is not getting hot.. ..

    correct information is important, for someone to try to diagnose the problem, 'remotely' when you or others ask for help!..
    kind regards
  7. Elvbee

    Elvbee New Member

    Ok, let be try and clear up the confusion, when I use the GAS to heat the water it gets hot but not as hot as usual. So in the mornings it's on between 5:45 to 9:00. Everybody get (3 people) get their shower by 08:15. If the 4th person try to get a shower at 11:30 the waster is cold. Normally the waster would stay hot the whole day.

    Using the IMMERSION heater it will take approximately 2hrs to heat tank, Yesterday the IMMERSION heater was on between 10am to 4pm and some time after 8pm someone was trying to take a shower and the water was cold and i mean cold. There are no leaks from Turk (or whatever it is called)

    One think I did noticed and I don't know if it's related (not a plummer so I am clutching at anything), There is wind noise coming from the furthest pipe in the house which is in the kitchen, which I believed means there is air in the pipe works.

    Sorry for the confusion
  8. Elvbee

    Elvbee New Member

    If one of the hot water pipe (to the radiator or otherwise) has a leak, would this drain out the hot water from the tank over a period of 1 to 2 hours?
  9. CraigMcK

    CraigMcK Well-Known Member

    if you have a leak on the hot water pipes and it's big enough, then yes, but you would see evidence of that volume of water. If your heating circuit has a leak, I don't see that reducing the temp in the tank.

    Are you seeing a drop in pressure on your boiler pressure gauge?

    Assuming your immersion heater is working, then it would suggest you do have a constant flow of cold water going in to reduce the temperature of the tank. From using it you will know yourself how many baths/ showers can be taken before it was getting cold, so you can understand how much water needs to be taken from the tank to cool it down.

    Might be time to get someone in to have a good look at it
  10. bobsy852

    bobsy852 New Member

    Did you ever find a solution to this? I live in a rented property flat with no gas. We have a megaflo immersion hot water heater which was heating up fine until last week. It heats up over night (on an economy 7 meter) yet the hot water has run out by the time I get back from work. If I put the boost heater on it gives me hot water again?
    I used to have red hot water all day.
    There's nothing dripping from the overflow, and I've kept an eye on my water meter to try see if the system was leaking but that doesn't move either without me using any water.

    Is there a fault with my immersion heater?
  11. plumberboy

    plumberboy Well-Known Member

    When heating on economy 7 does the water meter show any loss of water when you get up in the morning,if so the immersion is over heating and the temperature relief valve is discharging hot water and replacing with cold,which means not a great deal of hot left in the cylinder.If this is the case then you need a new thermostat fitted.;)
  12. Elvbee

    Elvbee New Member

    I had a burst pipe hot water under the house that was leaking out all the hot water from the megaflow within 2 hrs after the heating when off. I was disappointed with most of the plumbers that came around to diagnose the problem, most came up with possible cause that even I knew was rubbish. My builder mate came around and immediately say I had a leak. Pull up some floor boards and we could hear gushing water.
    Sean_ork likes this.
  13. tom1993

    tom1993 New Member

    Hi. I have a heatrae boiler with a mega flow un-vented cylinder. Iv had someone take all my radiators out cap then and switch off heating side of things, but I seem to only have luke warm water now. Any suggestions why?

    Attached Files:

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