Blockage in HW pipe behind built-in thermo shower mixer

[craftihand]

Scenario: Around 1991 I installed a Rothermix thermo shower mixer at chest level and an outlet for the fixed shower head about two feet above it, all set in recesses that I cut out of the clinker block inner skin of the wall to the bathroom. I used compression jointed pipewrk with Bosswhite.
It all worked fine. Soon afterwards my making good grout was covered when a contractor tiled the bathroom floor to ceiling.

After a few months the hot water suddenly stopped getting through and so only cold showers were on the menu. We carried on by using a flexible-lead shower from the plain mixer tap that I had fitted to the bath during the bathroom upgrade. Not being a dynamic man-of-action I have allowed that situation to exist now for twenty years. But now the bath and fittings are being renewed again, and I want to make every effort to get this impotent fixed shower working again, while keeping the wall tiling intact.

I can't escape the conclusion that I was too liberal with the Bosswhite and the blockage results from a surplus that has built up somewhere and nicely solidified. A Fernox product was suggested to me in the early days, but then I learnt that its use in domestic plumbing was forbidden, so I didn't pursue it. I can get to the H&C feeds under the floorboards quite easily and I am thinking of feeding compressed air into the HW pipe up to the mixer, using my tyre inflator which shows a max pressure of 350 lbs/sq.in. Possibly before that I would apply mains pressure.

That is Idea No. 1. Has anybody got suggestions, ideas, brainwaves, or miracles that could be applied to this, please?

Idea No. 2 is that I isolate and seal the hot feed from the floor to the mixer, then I fix a non-return valve to the HW pipe coming from the calorifier, then join that hot feed to the cold feed via a T jct. (still under the floorboards) so that when I turn the mixer on it draws both H and C water together, but up the cold pipe only, into the mixer. I believe the thermostat will still activate under these circumstances - so in theory I should be back in business. What do you think? Is this a practical plan or is it a pipe dream? Pun intended.

Please bear in mind that I have waited twenty years for all the brilliant responses I now hope to get from all the experts out there. Please don't let me down.

 

[Galoka]

That's an impressive wait for enough roundtuits, hat's off to you

The most likely blockage is at the shower valve , are there any filters? mine has them on the hot and cold feeds, you can access them by removing the front trim and handles.

if not maybe in the thermostatic cartridge (if old ones are lie modern ones)

 

[xr4x4]

How will the mixer beable to adjust the water temperature if it's already being supplied with both down one pipe already mixed?

 

[craftihand]

How will the mixer beable to adjust the water temperature if it's already being supplied with both down one pipe already mixed?

It can't, can it? I typed out nine lines of an answer to you to explain why it could, but as the logic came home to me I realised that if the mix were too hot then the thermo has no way of limiting the hot flow or increasing the cold.

This leads on to Idea No. 2a - which is that if I insert a normal in-line isolating valve for both hot and cold, and then experiment with the valve setting on each one, I should eventually be able to create a flow with a constant acceptable temperature. In theory this would be OK for me, and therefore would have to be OK for the wife. "If you use the upper shower you have to take the temperature you get. If you use the lower one, you have to adjust the H&C flows independently, as you have been doing these last twenty years." "Is that alright, Dear?"

The one drawback with that is that when the valve is first turned on the flow will start cold, and then the hot has to force its way into the mix. My experience is that takes longer than if it starts hot and then waits for the cold to get through - or maybe I'm just imagining that. Remember that this route will only be taken if I can't clear the blockage - and clearing the blockage is the main objective. But whatever: I do not want the wall tiling touched.

I don't mind how much my intelligence is shown up, or how much I am humiliated, I just wan't a solution.

 

[xr4x4]

If I was you I would go down the route of taking apart the shower valve, you should beable to do this without damaging the tiles.

It's properly blocked with lime scale, or other bits.

 

[craftihand]

If I was you I would go down the route of taking apart the shower valve, you should beable to do this without damaging the tiles.

It's properly blocked with lime scale, or other bits.

I did that first twenty years ago, and then again a few years back. I opened it up right back to exposing the hot inlet pipe - it was dry. I then turned on the hot supply (and not the cold) and not a drop came through. Behind that hot inlet there are three elbows in the run until it gets to the straight run down to the floorboards. Inside the mixer valve the space for manoevering is so limited that I can't fix anything to the inlet opening to apply either mains or air pressure.

I see that Fernox produce something to break down limescale, but limescale to block a 12mm pipe would never build up in just a few months, so I feel sure it's excess Bosswhite from all the compression connexions. Is there anything strong enough to break up twenty-year-old Bosswhite that is lawful in a domestic H&C supply? OR MAYBE the blockage is actually further away, like somewhere under the floorboards. THAT would be a lot easier to deal with. So maybe I should open up the pipework down there as a start.

 

[craftihand]

That's an impressive wait for enough roundtuits, hat's off to you

The most likely blockage is at the shower valve , are there any filters? mine has them on the hot and cold feeds, you can access them by removing the front trim and handles.

if not maybe in the thermostatic cartridge (if old ones are lie modern ones)

Don't know what a filter is (in a mixer), and don't know what a cartridge is. I've searched for a book called "Plumbing for Idiots" but I haven't found one yet. Meanwhile write to me as though I am an idiot and we might get somewhere. As you will see elsewhere in this post, I've had the mixer apart more than once and saw nothing I would class as a cartridge or filter. I would put the date of manufacture of the mixer at about 1985. It was surplus to requirements when my company built Swindon Hospital. Therefore I guessed it would be decent quality.

 

[Galoka]

[

Don't know what a filter is (in a mixer), and don't know what a cartridge is. I've searched for a book called "Plumbing for Idiots" but I haven't found one yet. Meanwhile write to me as though I am an idiot and we might get somewhere. As you will see elsewhere in this post, I've had the mixer apart more than once and saw nothing I would class as a cartridge or filter. I would put the date of manufacture of the mixer at about 1985. It was surplus to requirements when my company built Swindon Hospital. Therefore I guessed it would be decent quality.

My shower valve has 2 little mesh filters on the inlets, underneath a screwed little accesses point.

Thermostatic valves nowadays have removable cartridge that does the actual thermosttic bit. these can be removed from cleaning or replacement. whether you valve would have that I don't know

Anyway, yes, I would work back down the pipe until I found where the water was reaching.

I was goign to do crazy bodges, I would look at putting in a thermostatic valve somewhere else, maybe it would work just goign through the cold side of the valve.

Hmm, how about one of these digital jobbies - the bit that does the mixing is remote from the shower, you can just have a remote in the shower to operate?

 

[craftihand]

[

Don't know what a filter is (in a mixer), and don't know what a cartridge is. I've searched for a book called "Plumbing for Idiots" but I haven't found one yet. Meanwhile write to me as though I am an idiot and we might get somewhere. As you will see elsewhere in this post, I've had the mixer apart more than once and saw nothing I would class as a cartridge or filter. I would put the date of manufacture of the mixer at about 1985. It was surplus to requirements when my company built Swindon Hospital. Therefore I guessed it would be decent quality.

My shower valve has 2 little mesh filters on the inlets, underneath a screwed little accesses point.

Thermostatic valves nowadays have removable cartridge that does the actual thermosttic bit. these can be removed from cleaning or replacement. whether you valve would have that I don't know

Anyway, yes, I would work back down the pipe until I found where the water was reaching.

I was goign to do crazy bodges, I would look at putting in a thermostatic valve somewhere else, maybe it would work just goign through the cold side of the valve.

Hmm, how about one of these digital jobbies - the bit that does the mixing is remote from the shower, you can just have a remote in the shower to operate?

A bit far out - but at present all options are open. Perhaps you could explain to my wife, along the lines of:, "If you want to control the temperature, just kneel down and reach over and raise that floorboard - then reach further down until you feel a knob, then turn it clockwise for warmer and the other way for colder. Is that OK?" She'll understand, and she'll let you know in her own way that it is most definitely not OK.

 

[Galoka]

I'm sure you could arrnage a little sign with diagrams for her.....


Obviously what might work will dpend on the plumbing arrangements.

digital showers like this:

http://www.mirashowers.co.uk/onlinecatalog/results.htm?sectionName=Digital showers

Might be a more useful option (all manufacturers have them nowadays)

There is a box that is fixed remote from the shower (cupboard, loft, underbath etc.) this controls the mixing of the water, which is supplied to the shower down one pipe. The shower control is just an electronic control, connected by a cable, can be mounted anywhere really, so could be on wall outside shower.

You can also get wireless remote controls which can go anywhere really.

Possibly you could pipe the output from the digital shower box through the existing mixers cold feed?

 

[denso13]

OR MAYBE the blockage is actually further away, like somewhere under the floorboards. THAT would be a lot easier to deal with. So maybe I should open up the pipework down there as a start.

Do that first so you can start ruling things in or out.

 

[xr4x4]

OR MAYBE the blockage is actually further away, like somewhere under the floorboards. THAT would be a lot easier to deal with. So maybe I should open up the pipework down there as a start.

Do that first so you can start ruling things in or out.

I agree, could a valve been turned off somewhere on the supply?

 

[Galoka]

OR MAYBE the blockage is actually further away, like somewhere under the floorboards. THAT would be a lot easier to deal with. So maybe I should open up the pipework down there as a start.

Do that first so you can start ruling things in or out.

I agree, could a valve been turned off somewhere on the supply?

That would be rather annoying in this context

 

[craftihand]

OR MAYBE the blockage is actually further away, like somewhere under the floorboards. THAT would be a lot easier to deal with. So maybe I should open up the pipework down there as a start.

Do that first so you can start ruling things in or out.

I agree, could a valve been turned off somewhere on the supply?

That would be rather annoying in this context

It would; but in reality it is very highly unlikely, because the individual HW feed going up to the mixer is a simple unvalved tap off from the main run coming straight from the calorifier that supplies all outlets in this bathroom and also the second bathroom next door to it. As there has been no sign of flow restriction to any other outlet, that would mean the blockage would have to be in the short length of exposed pipe before it disappears bhind the grout and the wall tiles. That's only about a foot, with just two elbows in it. Very unlikely - but not impossible. It wouldn't duly upset me because, despite the twenty years, I still would never have expected it to get blocked at that position. Famous last words. We'll see.