How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Plumberpro Your Own Question
Plumberpro, Plumber
Category: Plumbing
Satisfied Customers: 634
Experience:  Heating and plumbing answers. 20 years experience
Type Your Plumbing Question Here...
Plumberpro is online now

Hi - my central heating expansion tank in my loft slowly fills

This answer was rated:

Hi - my central heating expansion tank in my loft slowly fills up with cold water over a period of 36 hours and then drips slowly from the overflow - never gets any worse than a drip. I have already changed the ball cock valve. The hot water storage tank has been replaced within the last 5 years and when that was leaking the water in the expansion tank was hot. I have exhausted all my limited knowledge now and need some help.

Regards Graham
Hello Graham

My name is XXXXX XXXXX I hope I can help you today. From what you describe with the dripping overflow. My view on that, is that the ball float attached to the valve arm is too high. This would allow the incoming water to rise and reach the outflow pipe. If you can lower the float or bend the arm down this will make the valve close more firmly.

I hope that this helps you

Customer: replied 3 years ago.

Hi Ivor - I've looked at this and if I remove some of the water so that the level is below the overflow outlet there is no water coming out of the ball valve at all at this point. I have to depress the float even lower to get any water to flow out of it. So I don't think this is the cause of the problem


Regards Graham

Hello again Graham. You said that there is a shower header tank as well. that was connected to the hot tank, which you have isolated. I was wondering if there is a siphoning affect from this tank to the main one. If that is so perhaps a non-return valve could be put in place between the two. This would allow water from the main tank to the mixer tank but not return back. If you could let me know I will get back to you, regards Ivor

Hi graham , if you need more help on this issue let me know
Plumberpro, Plumber
Category: Plumbing
Satisfied Customers: 634
Experience: Heating and plumbing answers. 20 years experience
Plumberpro and other Plumbing Specialists are ready to help you
Thank you Graham for your positive rating of my answer.

Thank you for using Just Answer. If you need help in the future just post your question and we will answer to the best of our abilities

Kind regards