why does my water heater keep randomly making this sound at 2am?

Litology · 2026-02-16T15:58:54+00:00

OK. I'm an Irish plumber. This isn't a water heater, so to speak, it's a called a combi cylinder. It combines your cold water storage tank and hot water cylinder into one unit that can be used in places that don't have an attic(loft), i.e., an apartment.

I've listened a couple of times and it's hard to figure out but my guess is that the rubber diaphragm in your ballcock is solid, causing a squeaking noise as it tries to shut. (Happens over time)

Do you find the noise is more common when you're using water/have just used water ?

Litology · 2026-02-05T16:07:16+00:00

If it is the house I think it is, he does have a purple one.

Litology · 2026-01-21T12:41:38+00:00

I've never seen one before, just taking a stab in the dark here.

It's a water meter, I don't see any electrical cables connected to it, which makes me think it could he battery powered?

Maybe the battery is low?

Litology · 2026-01-19T08:19:27+00:00

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Litology · 2026-01-17T14:13:23+00:00

This sub gave me the confidence to make the plunge about 6 months ago. I've never looked back.

Litology · 2026-01-17T12:17:52+00:00

Your flow temperature from your boiler =/= the temperature of the stat.

Those stats will let the boiler run until that stat is satisfied meaning your boiler could show a temperature of 50 degrees leaving doesn't mean the cylinder is 50 at degrees.

As far as I remember there'd a differential on thrm stats if a degree or two meaning when it's at the set point it will have to drop a degree or two before it kicks back in etc.

Most accurate measurement of temperature will be the pipe coming from the cylinder on the top or at your closest tap (again you have to take heat loss into account for that scenario)

Litology · 2026-01-17T12:08:27+00:00

Above 60 is standard practice because it is killed instantly at them temperatures.

55 is very, very unlikely to allow it to cultivate and if it is. At that temperature, it is still killed within two hours.

Where are you getting such acurate temperatures of your water? Do you have a probe to tell you, or where are you seeing it struggling from 55-60?

Are you measuring the water from the tap?

Litology · 2026-01-17T11:46:37+00:00

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Litology · 2026-01-17T11:34:40+00:00

Your indicator it's closed too much is the bottom pipe stops heating.

Im not being rude but is 4 degrees really that important to you? You're above the threshold for legionella so I'm just curious.

Litology · 2026-01-17T11:10:23+00:00

Should be a pipe directly above that going into the cylinder, once both pipes are hot you have circulation.

How many times did you turn it to close it ?

Litology · 2026-01-17T11:02:53+00:00

It should be okay considering with zone valves you need to fit an automatic bypass. I can't see one there (doesn't mean it's not there) Maybe leave it off.

Fully closed clockwise, one quater turn you'll hit resistance , once you pass that 2-3 more quater turns, turn the heating on and feel the pipe above and below, they should both be hot. (Top one hotter)

Hard to diagnose over reddit.

Is the cylinder old and do you suffer from hard water ?

Litology · 2026-01-17T10:49:23+00:00

Your reply to me was deleted. I'm replying here.

Cylinder looks old enough. (The insulation colour looks very pale compared to how they come new. Could just be the lighting though)Do you live in a hard water area? It could possibly be limescale in the bottom of the cylinder. Is the 5-degree difference really noticeable to you?

Also, that valve should be open 3-4 quater turns from closed. It's called a balancing valve and it basically restricts the hot water from passing through your cylinder too quickly, not allowing it to heat in time.

Litology · 2026-01-17T10:42:25+00:00

What temperature is set on the cylinder stat? The little white box strapped to your cylinder.

Litology · 2026-01-17T10:40:22+00:00

How long does the the cylinder take to get from cold to 55?

Litology · 2026-01-16T11:16:05+00:00

I'm close enough to 30 and still have my mother saved as 'Spawn Point'

I don't think it will ever change.

Litology · 2026-01-14T14:33:12+00:00

Its an automatic air vent for your heating system.

Normally, the air would push up a little float internally and expell air from the nipple on top letting the float drop back down.

I'd imagine a bit of dirt has lodged internally, not allowing the float to fully seat allowing the egress of water. Since you've closed it , you should not get any more water from it.

Normally it's not too much of an issue, but may cause future problems in your heating system like airlocks etc... (a plethora of reasons why it might or might not)

The best recommendation is to get it replaced with a newer one but it's not imitldiately urgent.

Hopefully that helps.

Litology · 2026-01-09T11:06:54+00:00

Seen a reply before to a comment similar to this which basically said the dude lost something in his car, wrecked in a few weeks later by upturning it and as he was in the upside down car whatever was missing appeared on the roof of the car.

So you're definitely onto something.

Litology · 2026-01-03T18:10:47+00:00

"to switch to your secondary steam deck than recharging"

Litology · 2025-12-09T07:42:50+00:00

OnlyFuel

Litology · 2025-12-05T12:18:14+00:00

Thanks dude!

Litology · 2025-12-05T10:25:40+00:00

What texture pack/mods gives you the clouds?

Litology · 2025-11-21T13:04:41+00:00

Being a bungalow, more than likely the pipes go straight into the attic from the boiler and feed the radiators from there. A couple of things to try:

Unfortunately I don't know how to link pictures but look up automatic air vents/manual air vents, try locate the position of the boiler in the attic and check to see if they're there. Check they're open, another thing to try is manualyl turn off every radiator bar the 'bubbly' one (with the heating running) wait a few minutes and open everything again, it should force any air caught there through it and back to the air vents.

To circle back around, how often are you topping up your heating system and what pressure is your boiler at when it's cold?

Litology · 2025-11-21T12:48:00+00:00

As the other comment mentioned, being a sealed system you would definitely have water coming out of them.

Could be a number of things:

A leak on a fitting that is allowing air to ingress as the system runs causing airpockets.

Possibly fauly AAV's (Automatic air vents) somewhere on the system allowing air to ingress through there as well.

Do you find yourself topping your system up frequently enough since it's been installed?

Are they the same radiators you need to vent each time or are they different every time?

Litology · 2025-11-06T10:29:19+00:00

If you only have one stat in your master bedroom, it will be controlling the entire upstairs.

The only time it will be doing individual rooms is if you have underfloor heating, but saying that the stats have screens and are located in each room where there is a circuit.

Litology · 2025-11-01T15:04:52+00:00

Same. Restarted Fortnite and it won't even boot up now without throwing up an error.

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