Hot water Cylinder "Gurgling"

2 Feb 2021
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United Kingdom
Today we had a visit from a BG engineer and his notes say replaced PRV in boiler. I assume this is a "pressure release valve"

Anyway since he left when my hot water timer comes on to heat the tank its like a loud gurgling noise next to the 3 way valve in the cupboard upstrairs.

Now when we run hot water in the kitchen the pressure is next to zero. It was pretty poor to start with but its a trickle.

On all the other hot taps, when ran they are incredibly hot so much so we have told the kids not to use.

And finally we have 2 showers, one fed from a cold tank in the loft and one fed from the hot water tank. The one fed from the hot water tank runs freezing cold and seems to be straining with a loud noise. Just freexing cold.

When hot water leaves the tank. I can hear it filling back up from the cold water tank in the loft.

So I am intrigued I get charged another excess from BG tomorrow when they come back out. Would changing this PRV in the Boiler ( Alpha CDS) cause these issues?

And all was fine prior to today. I know the three way valve is not jammed I can see it move when i switch from central heating to heating the water and back again.

Would replacing this part in the boiler introduce air into the system? And why would the shower not work?

Many thanks
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15-20 minute job and he never needed to go anywhere near anything to do with the HW Cylinder
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If it was all he did, then I’d say it’s purley coincidental. Unless he drained off without isolating the supply to boiler and caused a bit of air entrapment.
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The electric shower is from a pipe that feeds the cold watertank in the loft. Pipe stretches across part of the loft and down into bathroom. I cannot recall if it is a fed from the watertank or a feed off a pipe that feeds the watertank. (it was installed by previous owner)

I noticed on the boiler the thermostat was set at 9 by the engineer. I could have sworn it was 0 or 6 (Dial) so I turned it down to 6 and I can power my heating and hot water on without this loud noise. The noise from downstairs was like a running tap or a leak which led us to the cupboard with the hot water tank.

Now I say its the pressure release valve but could be anything. Documents just say fit PRV and no more.

He was here 45 mins or so.

With the thermostat being at 9 on the boiler controls which it never was in the past combined with a Hive thermostat cause issue - water was the hottest I have known it to be. I thought thermostat was set to 0 and Hive kit did the work. thermostat on the side of hot water tank is set to 65.

No idea what else he done, prob nothing. But a visit from BG to replace a part that was already working but previous engineer said he saw a bit of water so he will get it replaced (sunday) and he comes and replaces it and 20 mins later I get this loud continuous gurgling noise and a shower with no hot water. Could just be a coincidence. Its not the cash I have to pay, I will pay whatever needs to pay and a new shower I am just genuinely curious and wanting to learn more about these systems so I can troubleshoot in the future. Obv if i pay nothing then great, However I would never touch a boiler obviously. just the thermostat and the reset switch on the front when it used to cut out before a PCB? and fan were fitted last year.

So I have hot water out the taps still but none from shower. So who knows. 2 things happened since engineer was here. Shower was on fine this AM.

thanks for peoples replies. much appreciated .
Most electric showers are mains fed. If the other shower is running freezing cold, again it’s nothing to do with part replaced on the boiler.

Do you know if there’s an immersion heater been left turned on, or accidentally turned on? (Asking for hot water too hot issue).

The trickle downstairs, what type of tap is it?
Hi, one electric is mains fed from the loft either tank or off mains that feed tank. That shower works fine. The second shower is fed from the hot water tank. Reason I believe this as I was told by a plumber and when there is no hot water for a bath there is none for thos shower to use. Shower is through the wall from tank.

The tap at the kitchen sink has always been low pressure - the furthest away point from the hot water tank. Cold pressure is great from outside (for taps downstairs i believe) and cold pressure upstairs is from tank in loft.

The kitchen tap has been replaced around a year ago. Both taps had poor hot water pressure.

I am not aware of an immersion heater being left on. Or there being one. I do know that the boiler heats the hot water tank by what ever means it does (I just do not understand).

As I turn off hot water , and heating and turn both on or one at a time I can see the 3way valve moving.

I am heating the hot water for an hour just now and I will see if it comes through the shower as my three kids have just had a bath ( but prior to bath no hot water through the shower fed by hot water tank). However taps produce hot water but as I said I have no idea. If the shower heats up then I have no idea what happened but I am glad I took a video of it and the loud noises to show the engineer tomorrow.

so from a quick google I have a mira Sprint using a cold water supply and a triton power shower which i just went to check the name of and guess what - hot water now.

I am just glad I took the footage otherwise I would be going daft.

Sorry to bother everyone.
Sounds like air in the system ,hard to tell from the video .
The power shower takes hot water from the cylinder ( and cold from the loft tank).
The Mira is instantanious ,takes mains cold water and heats it electrically.
If the temperature of the hot water from taps / in the cylinder was exceptionally hot ,that's a control issue.
Hi there - just wondered if you got this sorted? Apols for jumping on your thread - I have similar noises coming from pipework into my indirect unvented cylinder after it was drained down after a repair (thats another story...!). I have similar air when the CH fires up so sounds like some air has got stuck in their. Originally, the engineer said the cylinder was locked, he freed it though - but wonder is it sounds like the freed air had now just worked its way into my primary circuit? If so (they are attending soon to look at it) should this be a fairly easy fix. Apologies for the basic questions...

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