Plumbing problem - overflow in downstairs toilet

6 Mar 2014
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United Kingdom
Hi All

Before i call out a plumber i thought i would see if anyone could shed light on what is causing this issue.

Whenever i flush the upstairs toilet or use the cold tap (never happens with the hot one) in the bathroom next door the plastic tank behind the downstairs toilet begins to overflow and bubbling can be seen in the toilet pan along with a gurgling noise :cry: This will continue until i flush the downstairs toilet. I think this is called backflow?

Also the upstairs toilet will on occasion now (usually when hasnt been used for a while) keep running for a minute or two long after the flush. Also often get a water hammer noise after flushing but not sure if this is related.

Thanks in advance for any help
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Sounds like two separate problems.

A problem with your downstairs float valve and a problem with the flush valve on the upstairs toilet.

If your downstairs WC cistern only overflows when the water pressure is varied either by opening a mains tap or flushing another WC then the float valve is not working correctly. However you really need to check it more thoroughly by removing the lid to the cistern see if the water level is where it should be. If not you should first adjust the float valve to get it right. If the cistern actually continues to fills up slowly until it overflows then try replacing the washer/diaphragm in the float valve. If you get a water hammer from this WC after flushing then I would be inclined to replace the float valve and I suspect this may be your answer to that WC

The upstairs toilet should not continue to run into the pan for any real length of time after flushing. If it does it suggests the flush valve is not sealing properly until there is enough head of water in the cistern to close it 100%. Cleaning the seal and seal seat may be all that is required, alternatively a replacement seal if damaged. I would anticipate the former. If it is this WC that generates water hammer then replace the float valve if it bothers you!

For further advice it would be best to upload photographs of the insides of each cistern as the variety of parts is too great to be more specific at this time. As it is I have made some assumptions!
Thanks for your time Blagard, much appreciated. Hopefully it is just something relatively minor as the float valves.
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Turned out to be the s & f gibbert filling valve in the downstairs toilet. Upstairs toilet running on was just down to the button getting stuck on occasion. Water hammer has been partially solved by turning down the water pressure and going easy when turning off the tap. :)

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