Backfiling Mystery - Mixer Shower Likely Culprit

[Denise Powell]

I had a leaking overflow pipe a few weeks ago and not only was the water running from my overflow pipe but the actual pipe (from the large tank in the loft) to outside needed replacing as it had several holes in it. I was rudely awoken in the night as water started seeping through my ceiling! My plumber changed the ball valve but my overflow continued to flow to outside.
I isolated my downstairs mixer shower and the problem was resolved but I wish to use this shower without my tank overflowing and sending water out the overflow pipe. As soon as I un-isolate the valves to use the shower then the tank overflows.
My plumber fixed a non return valve on the hot pipe just before the shower but this hasn't helped. The level in my tank rises very slowly and then overflows. I can see a slight ripple from one of the pipes at the bottom of the tank so clearly this is where the problem is coming from and a pressure issue.
Not sure if this is relevant but when I turn off my stopcock all taps stop working but my upstairs toilet continues to fill?
Can anyone please advise me what is causing this and how to fix it. I was convinced non return valve was the answer but sadly not. Many thanks

 

[townfanjon]

Yes you would think the NR valve would cure it , have you any mixer taps anywhere ?
The toilet is a mystery, possibility filled by the tank , obviously not correct but some plumber may have connected into the wrong pipe maybe

 

[snowhead]

Seems like the NRV isn't working.
Do you know what type of NRV was fitted and where in the pipe, is it Horizontal or vertical?

 

[Ben-gee]

Why is it not correct to fill toilet from tank? Surely hundreds of thousands are like this in the UK?

From what you say ; ie problem solved when shower isolated it must be a problem with shower.
Put NRV on BOTH the hot and the cold to the shower - possibly a faulty one has been fitted, remove and test this one.

 

[Denise Powell]

Just realised plumber fitted NRV to cold pipe instead of hot!

 

[Stigster]

Just realised plumber fitted NRV to cold pipe instead of hot!

There's your problem. As for your toilet still filling with stopcock off, it will be connected to the cold water storage cistern which is perfectly fine and normal. It can even be an advantage in certain situations. If the supply is turned off because they are doing work on the mains in the road for example you can still flush your toilet as long as the tank has enough water to replenish the toilet cistern. Of course that doesn't happen often but if it does it's nice to still be able to flush.

 

[Welder]

Just realised plumber fitted NRV to cold pipe instead of hot!

Sounds like the plumber should now be known as, "Our ex plumber" ! Bog basic mistake that in my book. Either incompetent or CBA.

 

[townfanjon]

Why is it not correct to fill toilet from tank? Surely hundreds of thousands are like this in the UK?
.

I have never seen one up here , maybe a regional thing.
The least fed anything from a tank the better in my book.

 

[Welder]

I have never seen one up here , maybe a regional thing.
The least fed anything from a tank the better in my book.

Much more common in the Saarf Jon. A few in Yorkshire (mainly corporation estates).

 

[Ben-gee]

That’s interesting TFJ, gravity is still common down here (Dorset), with just kitchen sink off mains.
Also quite common to have a 25 gal cws feeding the hot, with all colds off mains.

 

[Stigster]

That’s interesting TFJ, gravity is still common down here (Dorset), with just kitchen sink off mains.
Also quite common to have a 25 gal cws feeding the hot, with all colds off mains.

Same down here in Guernsey. I'd say we have approximately a 50/50 split between gravity fed systems and mains fed. Usually when an open vented cylinder goes a customer will opt to convert to unvented but there's still plenty of "old fashioned" systems in use too.

 

[townfanjon]

That’s interesting TFJ, gravity is still common down here (Dorset), with just kitchen sink off mains.
Also quite common to have a 25 gal cws feeding the hot, with all colds off mains.

Only gravity we need up ere is to fill our tin-baths mate .