Hello – thanks for looking at this – I'll try to be brief with just the facts:

• I have a Roper Rhodes SV1409 thermostatically controlled shower/diverter valve.
• It was installed by a plumber 4-5 years ago
• It worked very well up until a few months ago.
• The feed from the combi boiler is good and hot.
• There is a strong flow from both hot and cold.
• Even with the temperature control turned all the way up, the water temperature isn't quite hot enough. If I tease back and reduce the flow of the on/off control, I can make it a bit hotter.
• N.B. – the temperature stop retainer is not preventing rotation of the thermostat.
• So I have:
Removed and descaled the thermostatic cartridge.
Removed and cleaned/descaled the little hot-feed filter.
Finally – I REPLACED the thermostatic cartridge with a new one.

It remains the same with a not-so-hot 'hottest' temperature. I live in a flat and wonder if I should reduce the mains flow at the internal stopcock to get the same effect as easing back the flow with the on/off control valve (I have enough water pressure)?

Unless my water pressure has increased in the last few months, I can't understand why it no longer performs as it did. If I ran a bath, it really wouldn't be hot enough.

I have inserted a pic and diagram in case it helps.

Many thanks for your advice!

The cartridge has no adjustment other than the spindle that rotates for the temperature. it just 'plugs' in and is retained by a nut and retaining sleeve.

If you are referring to adjusting it by way of the plastic temperature stop retainer, I am testing it with that off for the moment because I want to see what the maximum temperature could be without it being limited. It's still not very hot.

I don't feel that the cartridge can be the culprit as the old one was no worse than this one.

Hello – thanks for that,

The adjustment on the temperature set up is on maximum, i.e. the retainer is not in place yet as I wanted it at the maximum temperature. It's still not very hot.

Yes, I cleaned both filters

Yes, the temperature and pressure at all other outlets is very good.

Hello – that's very kind of you to offer to do that.

I have already been on to the Roper Rhodes technical guy and beyond a service and descale and clean the filters, he had no other suggestions to offer. He sent me a new thermostatic cartridge which didn't work and that's when I got in touch with you.

Before I cover the bits you asked for – I can say that the mains pressure is very good at my flat. Perhaps too good. I wonder if the pressure increased for some reason a few months ago. I've noticed that if I restrict the flow by doing up the internal stop cock a bit, the shower does get hotter and still has sufficient flow.

Is there anything wrong with that solution?

Hello

OK, I've done the bucket test. I had to do this in the kitchen (it's right next door to the bathroom) because, of course I can't reliably isolate hot/cold in the shower because of the thermostat. The Cold took 23 seconds to fill 8 litres. The hot 27 seconds. So I think (roughly):

Cold = 21 litres/min approx.
Hot = 18 litres/min approx.

The boiler is an Ideal Independent C24 and was here when I moved in October 2015. I took the pic below of the serial number but it also has a date that may be when it was made (2005)?



Just as an aside – this morning I opened the internal stopcock from fully closed about 1/2 - 3/4 of a turn so that I still had acceptable flow but reduced. The shower was plenty hot enough and with a good flow.

I can still easily shut off the supply in an emergency – my apologies – I didn't quite understand why not opening the stopcock fully is a bad idea.

Oh right.  
Do you think that the pressure is unusually high? It does seem a bit harsh.

Can we reasonably assume it may not be a boiler issue?

I'm not sure I trust myself to tackle that kind job for the adjustable pressure reducing valve. I think I'd have to give that to a pro. I've been out of work for over a year so maybe it will have to wait £££. Not even sure where the external stopcock is  

I took the pic below outside my flat. The pipe goes into the kitchen which where the internal stopcock is. Does this look like a likely candidate for the external stopcock? I don't suppose I could give that a little tweak to reduce the pressure could I? Think I know what you're going to say – or that it's a gas pipe!

Here's a shot of the boiler and where I've pulled the washing machine out to get at the pipework – no pipes visible above the worktop. ...



...below the worktop. I have put the pics together in the order they run with a bit of overlap so you can see what's where. The stopcock is marked with a red arrow (and a label tied to it). There are two other spigots in the pic. One directly below the stopcock and one to the right and beneath the gas meter. No idea what they do...

Just FYI – The gas meter is in a corner. The wall where the white pipe and flexi hose is – is to the outside (where the old lead waste pipe pic was taken yesterday) and the wall where the stopcock and electrical socket is - is next door's kitchen.




Let me know if you can't make sense of the pics – thank you.

No problem, thanks for the reply. I'd have to remove a load if stuff and the plasterboard from the store cupboard that backs onto the shower but it's a good thought. There might be one of those isolating valves with the quarter-turn to stop the flow. Is it OK to partially close those or will that damage it too?

OK – many thanks for your help with this. I'll give that a try if they exist behind the plasterboard but I'm not sure if I'd know a cheap one if I saw one!