Electric shower runs hot/cold rapidly

[stealthwolf]

We moved into this house three years ago. It came with a gainsborough 10.5 SE electric shower. After a few months, the isolation switch stopped working and I replaced it. Other than that, it's worked perfectly well.

Until last night.

Swmbo went to use it and told me the water wouldn't come out properly. I've had a look and the shower runs for a few seconds, becomes scaldingly hot, safety clicks in, becomes cold, then water flow increases, becomes hot etc. Each stage lasts about 2-3 seconds.

The shower had a new hose last year as the old one had started leaking, and I've run the shower without the shower head attached to find it's still the same.

Any thoughts?

 

[ban-all-sheds]

Scaled up heater can is a strong suspect.

 

[stealthwolf]

I've played around a little now that I'm a bit more wide awake.

If I turn off the isolation switch, cold water comes out but the flow switch is a bit rubbish compared to what I remember previously when the isolator switch burned out.
If I turn on the isolation valve but remove the shower hose, it reacts the same: gets very hot, splutters, water flow stops, goes cold, starts flowing again, heats up and does the same.

If the heater can has gone, it probably means time for a new shower.

Is it likely to be the inlet filter?

 

[JohnW2]

If I turn off the isolation valve, cold water comes out but the flow rate is a bit rubbish...

I don't quite get that. Do you mean the water isolation valve? If so, when you turn it off there should surely be no water coming out? Have I misunderstood you.

If I turn on the isolation valve but remove the shower hose, it reacts the same: gets very hot, splutters, water flow stops, goes cold, starts flowing again, heats up and does the same. ... If the heater can has gone, it probably means time for a new shower. ... Is it likely to be the inlet filter?

What you are describing is, I imagine, what one would expect if something was gummed up and limiting the water flow to an unacceptable extent. It could be the filter, other parts of the innards of the shower (as previously suggested), or even the pipework.

Kind Regards, John

 

[stealthwolf]

I don't quite get that. Do you mean the water isolation valve? If so, when you turn it off there should surely be no water coming out? Have I misunderstood you.

I've edited my post. Should have isolation switch (pull cord).

What you are describing is, I imagine, what one would expect if something was gummed up and limiting the water flow to an unacceptable extent. It could be the filter, other parts of the innards of the shower (as previously suggested), or even the pipework.

I've isolated the electrical and water supplies and removed the cover. The protector over the inlet filter has a screw and there's very little space (about 50mm) so am about to have a look for a suitable tool.

I'm hoping clearing that the filter will sort things out. Otherwise it'll probably be more cost effective to replace the unit rather than hire someone to find and fix a fault.

Incidentally, I found some paperwork thay showed there was an electrical survey as well as new consumer unit and electric shower all fitted in 2009. So the shower looks to be about 9 years old.

 

[stealthwolf]

Well I managed to get to the filter. It had some crud on it but not much. Cleaned it off. Set everything back up again. Same problem.

Any other suggestions before I replace the unit?

 

[JohnW2]

I've edited my post. Should have isolation switch (pull cord).

Thanks - that makes more sense. If the flow rate is rubbish with the electricity turned off (assuming you get some flow - with some showers you don't without electricity), that certainly suggests that something is clogged up.

Well I managed to get to the filter. It had some crud on it but not much. Cleaned it off. Set everything back up again. Same problem. Any other suggestions before I replace the unit?

Not really. As above, it sounds as if something is crudded up, so that's probably the 'works' of the shower (and, as you've said, repair would probably not be cost effective).

I suppose it would be wise to rule out clogged-up pipes before you buy a replacement shower - i.e. by making sure that the pipe supplying the shower is capable of a decent flow. If you have a (water!) isolating valve close to the shower, that ought to be fairly easy to check (but you might get a bit wet!).

Kind Regards, John

 

[stealthwolf]

I suppose it would be wise to rule out clogged-up pipes before you buy a replacement shower - i.e. by making sure that the pipe supplying the shower is capable of a decent flow. If you have a (water!) isolating valve close to the shower, that ought to be fairly easy to check (but you might get a bit wet!).

Thanks. The water isolation valve is in the cupboard next to the boiler. I think I might remove the shower unit, run the water supply and see what happens. If it's all fine (as I suspect it will be), time for a new unit.

Any favourable or preferred brands?

 

[JohnW2]

Thanks. The water isolation valve is in the cupboard next to the boiler. I think I might remove the shower unit, run the water supply and see what happens.

That's what I was suggesting, but if the isolation valve is distant from the shower, it's probably best done as a two-man job (unless you don't mind want a lot of water flying around)

If it's all fine (as I suspect it will be), time for a new unit. Any favourable or preferred brands?

Yes, it will almost certainly be fine - but it's probably worth checking before you fork out for a new shower. As for brands, it's a long time since I've bought one, so you'd better rely on someone else for advice/recommendations. I've always tended to go for the big (hence most expensive) names, but various friends and family have had years of satisfactory service from cheapo ones, so I'm not convinced that there is necessarily a lot of difference.

Kind Regards, John

 

[flameport]

Otherwise it'll probably be more cost effective to replace the unit rather than hire someone to find and fix a fault.

Gainsborough showers have no serviceable parts - the entire thing inside is a single unit, and it's designed to be non-repairable. Described as a 'Shower Engine' by the manufacturer.
They scale up inside and once that has happened, there is nothing you can do other than to replace it.
You can buy a replacement 'engine' for about £80, or an entire new shower is about the same.

Other manufacturers are available, and have showers for similar prices, slightly more work perhaps as the pipework and wiring may need to be in different places.
Expensive electric showers are no better either - but after paying £100s for one, you will feel compelled to spend money repairing it rather than replace.

Or take this opportunity to fit a proper shower instead of a feeble electric effort.

 

[stealthwolf]

You can buy a replacement 'engine' for about £80, or an entire new shower is about the same.

It's also rather tricky to get hold of. I looked at alternative instead.

Expensive electric showers are no better either - but after paying £100s for one, you will feel compelled to spend money repairing it rather than replace.

TBH if this unit has lasted 8-9 years, that's not too bad in my book. I ended up buying a Mira Sprint something or other that advertised the fact it could be plumbed and wired in from both sides. Turned out that to do this, I needed some copper pipe and elbow bends, which it doesn't mention (other than an accessory kit in the instruction manual that does the same thing). Thankfully I had loads left over from when I installed my kitchen mixer/filter tap.

Or take this opportunity to fit a proper shower instead of a feeble electric effort.

Currently the pipework and wiring runs from the loft and inside the bathroom wall, so without an overhaul, I'm stuck with electric showers. I'd much prefer a nice mixer shower with mains pressure behind it.

 

[stealthwolf]

Well I ended up buying a Mira Sprint 9.5kW shower from screwfix as it was the only one both in stock and able to accept inputs from either side.

Frustratingly, as I pointed out in the post above, it required extra plumbing to take a feed from the right lower side of the unit to the left middle side. No leaks so far *touch wood*

Drilling the mounting holes in thick tiles took the longest bit of any job. I started off with Bosch multi construction bits and after about half an hour of near continuous drilling, I managed a dent about 3-4mm deep. I bought some cheapo porcelan drill bits from screwfix and it still took another thirty minutes to get through about half the thickness of the tiles. I ended up going back to my Bosch bits and using the hammer drill. Still took about 15 mins per hole on top of what had already been done.

Plumbed it all in and turned on the isolation valve. No leaks. Had to trim the wiring to suit. No issues. My only complaint is that the cover doesn't quite accept the wiring (it comes in just above the pipe and bends upwards 90 degrees), so there's a little bit not covered by the plastic casing.

The only other complaint is the whoever fitted the shower last put silicone sealant in and around where the pipe and wiring come out of the tiled wall. About 5cm by 5cm and who knows how deep.

 

[ban-all-sheds]

Any favourable or preferred brands?

Redring Selectronic.