Home DIY

Boiler/shower:

The shower head is fed from a diverter valve that is part of the bath taps, you pull the collar up to send water to the shower head and then adjust the taps to the correct temperature for your shower.

The boiler is a combi, which has been running non-stop to try to keep the cold at bay.

The situation: both the shower and the hot tap in the kitchen exhibit the same behaviour - turn the hot tap fully on and it will swiftly produce steaming water, then the water becomes freezing cold, then steaming hot, then steaming cold, then settles down to being hot.

This is kind of annoying in a doing the dishes scenario, but manageable. In a "I have to catch a train shortly" sense standing there waiting for the shower to stop it's hot/cold/hot/cold cycle is frustrating, but not as frustrating as standing in the bath with your eyes shut as your face is covered in soap, poking a foot into the water coming from the shower head to establish if it's gone back to being warm again.

It's got a new wrinkle over the past two days - once it's past it's hot/cold/hot/cold behaviour it's now very hard to get it to a temperature that humans appreciate - it's either scalding hot or tepid, and the Eddie Izzard safe cracker sketch applies here. However! As you try to dial in the fraction of a degree required on the cold tap you can see the shower hose jerking as the pressure fluctuates quite significantly, and the temperature drifts down over time as well, so you have to repeatedly crack the safe.

All of this turns a five minute shower into a 15 minute shower, much of which is spent observing the shower closely whilst trying to get into it without horrifying pain/debilitating coldness resulting.

What do please?

My mate who has been a decorator all of his life gave me this advice once (and I have always used this method since with zero issues):

"If it hasn't been painted you need to put a mist coat on it (which is a watered down coat). It needs to be like coloured water (It will go everywhere!!!)

Ideally it needs to be a paint with out plastic in it, so a Dulux super Matt.

For the final coats you need somethin with plastic in it, like a vinyl Matt. I personally only use Dulux. "

Turn the temperature down on the hot water to something non-burny. See if it helps.

Boiler sounds like it needs tlc though.

It’s set bang in the middle right now which is 50 degrees c according to the panel- set to 45? I don’t want to go much lower as I assume there’s going to be a loss en-route to the shower.

1 Attachment

Sounds plumbery

From that thread it may need a new heat exchanger- I’ll get a plumber to come and look at it.

You’ll need to call an engineer, the plate heat ex is fucked

so do you do mist coat with dulux super matt, then a coat of super matt then a vinyl matt? or two coats of vinyl matt? sorry if dumb question

1x watered down Dulux super Matt mist coat

Then as many top coats of vinyl matt as you need for coverage (I always think you need three but that may be my shit rollering)

A lot depends on the final colour and the opacity of the paint that you are using for the top coats.

If your finish colour is white then mist + 2 coats of super matt on the ceiling, mist + 2 coats of trade diamond matt in a hallway/bathroom.

Most of the finish colours I get asked to paint are F&B colours or Little Green, Designers Guild etc. I always get the client to order them from the manufacturer as getting them mixed in Dulux or Leyland etc can lead to disappointment. F&B stronger colours usually need a few coats for complete coverage. Little green will sometimes cover in 2. Designers Guild is a Mylands paint, I've not used their darker colours but the lighter ones have a nice base with good opacity.

Just want white - so will this do the job ? Is it suitable for bathrooms?

I like it for hallways, it works pretty well for bathrooms without getting into the traditional alternatives like eggshell. It has a slightly more plastic finish which can be washed more aggressively without it scrubbing off the walls.

Nice one cheers dude!

Ok, plumber says absolutely nothing wrong with the boiler, although he can’t explain why the shower hose jumps around with (assumption) pressure fluctuations.

His recommendation is to set the water temperature to a comfortable showering temperature and not add any cold water at the mixer tap.

Well that’s good. Do you believe / trust him?

I had a shower like that before, it didn’t flip between hot and cold but it needed to be adjusted perfectly with the hot tap full on and tiny movements of the cold tap to get it right.

You can get thermostatic bath tap mixers with shower fittings - I dont know which brand / model is any good, but those are examples. Then the temp is set at the tap. Feels like fixing the symptoms not the cause though.

I thought you said it happened on the kitchen tap too, so it surely is the boiler?

Obvious question but you're not using the dishwasher/washing machine etc at the same time are you?

Also is your boiler on eco mode? On ours, all that does is prevent the boiler from doing it's normal thing of keeping a little bit of hot water ready to go as soon as you turn on the taps. Doesn't seem to make much difference to energy use and means you have to wait longer before the shower temperature steadies out.

TBH if you'd said it was happening at the shower only, Id have looked at the shower but from what you said and it was happening at multiple outlets I'm surprised its not the plate as that's what is common for the description.

Our shower has the same symptoms as yours. I am waiting for an engineer to service it in the next couple of weeks. My NOTION is that when a tap is turned on hot water fills the pipes. When the shower is turned on that hot water comes out. Behind the hot water is cooler was which has cooled in the pipes. As it comes out the shower it is followed by hot water again from the boiler. That’s my theory - hope it makes some sense.
You could try the immediate hot water function on the boiler - that could help. My engineer said it is a costly option so I have never used it. Our gas bill is currently £382 per month and I’m struggling with that!!

The plumber asked me about the kitchen tap and shower - specifically he asked whether the kitchen tap started cold, went hot, then cold, then hot again and stayed hot, which I think it does.

Which he said is normal for a combi boiler system.

The shower definitely cycles up and down more than this - or it did.

I had the best shower that I have had here earlier, hot tap only and the water temperature set on the boiler. One thing that was noticeable was that the hose didn't jump around during the shower either.

So - lets see what it does tomorrow, but if it's like today then that's ok.

That is not my experience of combi boilers! Cold until hot and then hot until you turn it off.

But good that changing the temperature made the shower good

I can tell you from workinb on them, that’s not right. It should be cold then stay hot for as long as the tap is open.

Shouldn’t go cold hot cold hot.

If others are using another shower/sink would this make a difference?

That could happen in that case, but reading into what the OP wrote its as if he runs one and it runs hot cold hot cold and not both at the same time. Gotta mind that you'll only get X amount l hot our your combi at once and if you have something that has multiple draw offs at one time you need a tank.

Thanks. If you can find my post previously it may explain our situation - or maybe not! Hard to explain without being here. I have hot, cold, warming and hot for the reasons I tried to explain. I’m just hoping it’s nothing costly!

@Dammit is the cold water pressure significantly greater than the hot?

A pressure mismatch can mean the stronger flow forces its way down the weaker flow rather than coming out of your shower head.

This has resulted in the safe cracking shower adjustment situation for us.