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Pinhole leaks and pitching

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  • 30-05-2011 12:31pm
    #1
    joeirish
    Registered Users Posts: 452 ✭✭


    Hi

    I have a dual central heating system, oil fired and solid fuel (Stanley range). There are two motorsied valves that ensure the hottest source is used to heat the water. The solid fuel part was installed twelve years ago and the oil fired boiler was installed six years ago.

    Over the past four years I have had to replace most of my radiators (ten in all) due to pinhole leaks. After the first five leaked I contacted the plumber who installed the system and he found that he had put a vent pipe in the wrong place on the oil fired C/H, which caused hot water to be continuously pushed over into the header tank (is this called pitching?). He sorted that but recently 3 more rads have started leaking with pinholes appearing. I have now discovered that the solid fuel system is pumping hot water over into the header tank from the vent pipe.

    When the pump is at greater than 1 setting then this happens.

    Is this the cause of the radiator leaks? Some plumbers I have spoken to say that as long as it is the same water circulating then this will not cause pinhole leaks but I have also read that water can get oxygenated if it is pumping via the header tank.

    The second question is what to do about this? I am not confident in the plumber who did the work. I spoke to a heating engineer a few months ago who suggested the system may need to be re-balanced(?) or something. Does anybody know about this? Something to do with linking the vent pipe into the feed. I've lost the guy's number so I cannot contact him.

    Any help gratefully received.

    thanks


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    #2
    Sparkpea
    Registered Users Posts: 1,118 ✭✭✭Sparkpea


    In my opinion yes this is most certainly the cause of the leaks. You will need your system chemically powerflushed (cleaned) and inhibitor added. Saying that, the damage is already done/started so this may not help much further tbh!


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    #3
    joeirish
    Registered Users Posts: 452 ✭✭joeirish


    Sparkpea wrote: »
    In my opinion yes this is most certainly the cause of the leaks. You will need your system chemically powerflushed (cleaned) and inhibitor added. Saying that, the damage is already done/started so this may not help much further tbh!

    Sparkpea

    Thanks for the reply. If the pumping over is the cause of air gettin ginto the water, what needs to be done to sort that? It would seem to me (but I'm not a plumber) that the cause of the problem needs to be sorted before I start the next stage.

    What is chemical powerflushing? I have put Fernox through the system already.

    Thanks


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    #4
    Sparkpea
    Registered Users Posts: 1,118 ✭✭✭Sparkpea


    there's different ways to stop pitching, a automatic byepass valve can help, other simpler ways are increasing the size and length of the expansion pipe, e.g. if its 15mm change it to 22mm or 28mm, if its 22mm change it to 28mm. If the pipe is extended to the highest pitch of the roof and back down into the tank that also helps, Means the pump needs to work harder to pump it over. If your tank is on a stand in the rafters you could drop it to the ground, or closer to the ground depending on what pipes are being heated by gravity. Its hard to say without seeing the job. Other methods are creating a loop in the cold feed, or piping the cold feed and expansion into one but I'm not a big fan of this.

    Fernox protector is only good if the system is clean, its not a cleaner. The system needs cleaned and then protected.


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    #5
    joeirish
    Registered Users Posts: 452 ✭✭joeirish


    Sparkpea wrote: »
    there's different ways to stop pitching, a automatic byepass valve can help, other simpler ways are increasing the size and length of the expansion pipe, e.g. if its 15mm change it to 22mm or 28mm, if its 22mm change it to 28mm. If the pipe is extended to the highest pitch of the roof and back down into the tank that also helps, Means the pump needs to work harder to pump it over. If your tank is on a stand in the rafters you could drop it to the ground, or closer to the ground depending on what pipes are being heated by gravity. Its hard to say without seeing the job. Other methods are creating a loop in the cold feed, or piping the cold feed and expansion into one but I'm not a big fan of this.

    Fernox protector is only good if the system is clean, its not a cleaner. The system needs cleaned and then protected.

    Thanks again.

    I can't move the tank otherwise there won't be enough head for one of the radiators in a bedroom (single story house with one bedroom in the roofspace). I'll try extending the vent pipe first into the highest point of the roof. If that doesn't work then I'll have to put in a bigger pipe as you suggest but that'll mean changing the tee. Ah well.

    The Fernox I used in F3 Cleaner. Should that do?

    Thanks


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    #6
    Sparkpea
    Registered Users Posts: 1,118 ✭✭✭Sparkpea


    if your tank is already high to feed the loft radiator then you probably wont get much more height on it tbh. F3 cleaner is meant to clean the system if left it in for a week or so then drained out but tbh imo it cannot but compared with the likes of powerflushing - but its a start.


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    #7
    2 stroke
    Registered Users Posts: 2,921 ✭✭✭2 stroke


    Why not just leave the circulating pump on the lowest setting?


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    #8
    Sparkpea
    Registered Users Posts: 1,118 ✭✭✭Sparkpea


    2 stroke wrote: »
    Why not just leave the circulating pump on the lowest setting?

    perhaps at 1 its not pumping around the system effectively.


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    #9
    joeirish
    Registered Users Posts: 452 ✭✭joeirish


    I meant to reply with an update. I turned the pump setting down to 1 and lengthened the expansion pipe as suggested by sparkpea. Now I don't get any pitching over. So thanks for the help on that one. Now I have another issue but maybe it's not an issue at all!

    The water in the header tank is still getting warm, and this seems to be happening by heat coming up through the feed pipe from the tank to the system. Now I don't know if water is being pumped up the feed pipe or if this is just convected heat. Any ideas?

    Thanks


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    #10
    Sparkpea
    Registered Users Posts: 1,118 ✭✭✭Sparkpea


    would the water be warm/hot/roasting? as hot as a radiator?

    the water in the expansion tank will get warm/will heat while the heating is on and the water level will rise but it shouldn't be roasting. I'm assuming its probably ok because normally the reason why the cold feed would get very hot would be because of a blockage at the expansion tee so instead of pumping out the expansion it pumps back up the cold feed but your expansion was clear not long ago so im sure its not blocked :)


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