Central Heating issue - WWYD?

[Lennybythewood]

So it seems I have an issue with my central heating. There's been a bit of a rattle from the pipes for the last couple of weeks and today I noticed a watermark on my kitchen ceiling - not wet to touch but definitely a watermark. The heating does still seem to be working ok though.

Obviously, I'm going to call someone out to have a look at it tomorrow, but in the meantime should I leave it off completely bearing in mind it's below freezing outside? Thinking more from the perspective of the potential for frozen pipes than anything else.

What's above the kitchen? Could be plumbing rather than central heating

does your boiler have a pressure gauge?

is there a hot water cylinder? what colour?

is the bathroom above the wet ceiling? Which appliance, in particular, above the mark?

Is the hot water tank situated above where the watermark is?

Also, if the tank is there, what type of heating system is it?

And is water coming out of the overflow outside the house?

@PigletJohn

does your boiler have a pressure gauge?

is there a hot water cylinder? what colour?

is the bathroom above the wet ceiling? Which appliance, in particular, above the mark?

No pressure gauge on the boiler. The bathroom (and bath) is above the kitchen, so could potentially be unrelated to the central heating - I just went with the assumption that the two were connected. The water mark is a long thin line that extends beyond where the bathroom would be and the rattling pipes are somewhere around the hot water tank, which is a few feet further away from where the water mark ends.

Lenny a very amateur guess would be that your hot water tank needs re-pressurising.

@goodbyestranger

Lenny a very amateur guess would be that your hot water tank needs re-pressurising.

I am hoping it's something straightforward, but at this point I'm assuming that it's time for the entire system to be overhauled. The boiler itself is 25 years old and I was told 10 years ago it was on its last legs - it's been serviced regularly and had the odd inexpensive hiccup since then, but I do think its time has finally come!

You mean boiler rather than tank?

Dripping suggests tank that's all.

Yes, talking specifically about the boiler but the tank is just as old and may well also need to go.

You don't want the drip to turn into a whoosh though. I had what I think is this exact problem two years ago. I had to replace the tank but not the boiler. Call a plumber first thing but it's so cold I'd tend to leave the system on overnight, maybe leave a bucket underneath the water mark. Also, if you look in the hot water tank cupboard you may well see the source of the problem (check all the valves).

What system is it? Do you mean there is a hot water cylinder above? Do you have feeder tanks in your loft space? Where is your boiler?

Think the terminology is getting mixed up tbh. Tanks are normally in the loft. Cylinders hold the hot water. Boiler heats the water for heaters/hot water cylinder

@dementedpixie

What system is it? Do you mean there is a hot water cylinder above? Do you have feeder tanks in your loft space? Where is your boiler?

The hot water cylinder isn't directly above, probably about 6 feet away. There is a feeder tank in the loft and the boiler is in the kitchen (opposite side to where the water mark is)

Correct! I mean the hot water cylinder. That was what I needed to replace. It's on the first floor and the dripping appeared in the room below several feet away from the cylinder itself because the water was running along the intervening boards/ beams.

What colour us the cylinder?

Bleed the highest radiator in the house. Does water squirt out forcefully and without dying away?

Look for the pump. Is that what rattles? (Usually painted dark red)
www.screwfix.com/p/wilo-4035479-sb30-secondary-circulating-pump-230v/74599

The cylinder is green (even has the original 25 year old sticker on it!).

The rattling is definitely coming from the vicinity of the pump - this was actually replaced less than a year ago :(

Annoyingly, the highest radiator appears not to be heating at all so a bit nervous about bleeding it, might leave that for when the pros turn up.

Try bleeding it. I suspect nothing will come out. If this is the case the pump may be running with air in it and may overheat or seize. Tomorrow I can tell you how to try and fix it. You will need to be in the loft with a torch, bucket and tools.

Neither the boiler nor the cylinder are pressurised so cannot be pumped up or repressurised.

The pipes rattling is likely to be air in the system, especially of one radiator is not heating.

Bleed the system as a starting point.

As for the leak, first port of call would be check the sealant round the bath etc, reseal it if needed. Then if it is still damp or getting bigger you may need a plumber.

You were right, nothing comes out. Think that me trying to fix it tomorrow would be a step too far - I'm embarrassed to admit that the only tools I own are screwdrivers, but thank you so much for your help.

OK.

The problem you have is fairly common with an old, open vented system.

Almost certainly the cause is this:

The steel radiators suffer corrosion due to containing water, and a small amount of dissolved air. This results in tiny particles of iron oxide (black in this case). The particles accumulate into sediment, much of it settles in the bottom of radiators; some in the poiler; and some in the pipes. If the water is hard it can aggregate with limescale to form a hard blockage.

most likly you have got a blockage in the pipe that comes down from the small feed and expansion tank in the loft and joins the main pipes, usually near the pump. It will be a 15mm pipe.

As it has hardened, the plumber will probably have to cut out the blocked section of pipe, and replace with a new piece.

i strongly recommend you to ask for a Magnaclean or similar to be fitted, it will trap other circulating particles before they can gather into another blockage. I would also advise a chemical clean, which you can DIY at trivial cost. Otherwise, the plumber/engineer will probably recommend a Powerflush, which will cost hundreds of pounds.

Whatever you do, get the Magnaclean fitted, the sooner the better. It will cost around £100 plus fitting. Black iron oxide is called magnetite and is attracted to a magnet. There is a powerful magnet in the filter that traps is. Brown rust is hardly attracted at all. Central heating sediment is mostly black iron oxide.

If you can't get a plumber tomorrow, look for the drain cock and a hosepipe and I may be able to help you top it up. The pump will wear out if run dry.

@Lennybythewoodas

p.s.

don't bleed any of the other radiators.

the system already has too little water in it, and the blockage prevents it refilling.

Thank you so much for this @PigletJohn, I really appreciate your help.

Do you think the water mark on my kitchen ceiling is completely unrelated and there could be a separate plumbing issue in the bathroom? The sealant around the bath is completely intact and is only a few years old.

might be.

water marks on the ceiling under a bathroom are most often due to leaking or overflowing baths, basins, cisterns, waste pipes etc.

I like to poke a skewer through the wet mark so that any water can drip out into your bucket, rather than soaking into the plaster. If you are lucky the hole can be over your sink, and no bucket needed. It is easy to fill and repaint a skewer-sized hole.