Ideal Standard mixer shower mystery

[MateyBoy]

Moved into a 10 year old house couple of years ago. Shower has its own feed from cold tank, and from surrey/essex flange for hot supply. Gas central heating conventional boiler.
In summer, shower is great. As we move towards winter, and in winter, in order to make the shower a bearable temperature, I move the mixer lever to the cold side, but the whole shower slows to a trickle. To get a 'decent' flow, the temperature is just too hot to stand under. (Tank temperature, by the way, is set at about 45 so that tap water is hot but not scalding.)
Other factors: gate valves on both supply pipes, but even when closed, there is still a dribble - dodgy gate valve(s)? Last time, I also turned off the cold tank to hot tank gate valve, and that more or less stopped flow.
Mixer is Ideal Standard non-thermostatic, and they say a new cartridge is still obtainable. Do you think that would sort out the problem, and any tips on how to fit a new cartridge?
Thanks in advance.

 

[WaterTight]

Over my head but I'm sure you'll get some helpful replies. I can't think why the shower would be too hot in the winter (but not the tap water.) Maybe the heating being on is causing something to happen to the DHW - but just the shower? Restricted cold flow (maybe from gate valve stuck half closed) possibly making problem worse. A thermostatic shower might help but you'd probably just end up with a pleasingly temperate trickle automatically.

Perhaps easiest and cheapest thing to try first would be to change faulty gate valves since you realy should do that regardless.

 

[Paulus]

I'm as mystified as Watertight, did this also happen last winter or is it a recent problem?

 

[MateyBoy]

Yes, it happened last winter too, but we hoped we would be able to afford a new combi boiler this year (so the tank & pipes would have been ripped out), but I'm afraid that that has had to be postponed indefinitely. Access is a nightmare (to the mixer), and because it is such a peculiar problem, I began to wonder what part the cartridge in the mixer might have in it. Must admit that Ideal Standard queried some sort of blockage in the supply pipes.
Just thinking aloud, but when I'm moving the lever to 'colder', the total flow is being throttled back: in summer, the temperature handle is more or less at 6 o'clock or 7 o'clock, but now it is between 4 o'clock and 5 o'clock.

 

[MateyBoy]

Gate valves seem to have a pretty poor reputation - is there anything superior?
Obviously, in summer, the boiler is only heating the hot water, whereas now it is hot water and central heating, so maybe the tank is getting a wee bit hotter, but because we don't want to risk scalding the grand kids, it is not as hot as some places seem to recommend. (What you can bear on your hand is a few degrees more than my scalp, shoulders, and any sticking-out bits can tolerate!)

 

[Paulus]

It is more likely to be the gate valves than the thermostat and as these are cheaper than a thermostat I would replace them first, especially as you know that they are not operating properly anyway. There should be a filter on the inlet pipes to the mixer, it is possible that the cold is gunged-up.

I have never used anything but gate valves and am not aware of an alternative which will give full bore when open.

 

[Best]

I have never used anything but gate valves and am not aware of an alternative which will give full bore when open.

The large lever type ball valves often are full flow. I use them on all hot pipes & think I will use them for most other supplies as they are the best.

 

[dancinplumba]

hi a bit concerned that you only have tank temp at 45 degrees. this could cause legionella to form

 

[MateyBoy]

Thanks dancinplumba! You've opened a whole new can of worms!! There seems to be loads of contradictory advice from all round the world on the subject of Legionnaires v. Scalding. Impossible to know who's right, but you have raised an extremely important topic, which could probably thrashed out in another Thread.
In the meantime, I HAVE turned the 'stat up to 50.

 

[dancinplumba]

oops... think it should be sixty...at least once a week to disinfect tank imo

 

[WaterTight]

Replace faulty gate valves with these

Full Bore Lever Ball Valve 22mm | NoLinkingToThis

If that doesn't solve it at least you have eliminated that as a cause and will have functioning isolation for mucking about with shower which will prob be your next port of call.

 

[MateyBoy]

Thank you, WaterTight. One step at a time might just get this sorted!

 

[WaterTight]

Fingers crossed!

(obviously get 15mm ones if you have 15mm gate valves)

 

[PlumbBobBob]

mateyboy i can confirm that your tank stat should be set at 60 to kill bacteria including legionnaires