Understanding the Hot Cylinder System

kuksucouple · 28-08-2024 01:57PM #1

Hello all,

We just recently moved to Ireland after living abroad where we have not encountered the cold attic tanks with hot water cylinder system. After buying our house here that was built in the 90’s, we are still struggling to fully understand how all the different parts work for general maintenance or troubleshooting. A plumber was here recently to fix a leak in one of the bathroom taps, but he was unfortunately too grumpy/busy to be bothered to answer our questions to understand it so I come here for any and all inputs kind souls here can advise on.

We have a central gas boiler in the kitchen downstairs with cold mains feed valve under the kitchen sink. The gas boiler is only a few years old, and have control for heating taps vs. radiators. Then we have two large attic cold water tanks and then a hot cylinder in the hot press upstairs. I’m mostly confused with all the pipes and valves coming off from the hot cylinder.

I attach a few photos here, and would be utterly grateful if you can help answering the following questions for my better understanding:

What are all the parts/pipes/valves labelled on the attached photos?
Is there a way to shut off cold and hot water tap feeds for bathroom sinks from the valves here?
I did not see any valves under the updtairs bathroom taps/sinks. Is it not possible to isolate just one sink tap feed at a time?
What is that red thing attached to the hot cylinder?
I believe we have an immersion coil for our hot cyliner. How exactly does this work? It was switched off from the house sale and we left it as is, but it looks like it has sink/bath controls?

Thanks so much in advance!

Best,

Angela

10-10-20 · 28-08-2024 02:46PM

Hi, Welcome!

This is actually hilarious, but it's something that we all take for granted here and don't think twice - but yet it's confounding to new arrivals. 😁

The Irish domestic hot water system is an indirect heating system - we use a coil in the cylinder to indirectly heat the tap water and this is augmented or backed-up by an electrical element also hidden in the tank.

1 & 2: These are the feed and return to the water heating coil in the cylinder. Top is usually the feed (hot water off the boiler downstairs) and bottom is usually the return (cooler water return to the boiler). So any pipes connecting to those two are related to the water heating system.

3: Feed pipework to cylinder from boiler

4: Fill pipe from the attic tank or off the mains (I see a one-way valve further up on pipe 4, suggests it's cold water tank fed?)

5: Hot water from cylinder to taps

6: Cold water from attic tank to taps

7: Return pipework to boiler

8: Expansion vessel for boiler circuit

9: Earth bonding loop for copper piping

10: Isolation valve fitted to the feed off the boiler - for some addition to the system - possibly a new radiator…?

11: Isolation valve on fill pipe (#4) from cold water tank in attic (to isolate the attic tank if needed)

12: Isolation valve on cold feed from attic tank to taps

13 & 15: Probably the "cold riser" from the Irish Water supply up to the attic tank(s).

14 & 17: Not sure… some modification, maybe related to #10.

16: Immersion element with the manual bath/sink switch.

Hope it helps.

kuksucouple · 28-08-2024 03:16PM

Dear kind soul on the boards.ie,

Many thanks for your super detailed response, indeed, I assumed this is very basic and normal system here but we are both going mad not being able to understand these. So very much appreciate your help 🙏

One follow up question is, so I do not see any valve for (5), the hot water from cylinder to taps, meaning that I cannot seem to be able to shut off hot water for any plumbing work on the hot taps. Is this normal? Is my alternative shutting off mains and draining the cylinder? I’m used to having valves under each sink mixer taps, handturning hot and cold feed valves…

Thanks a million again!

10-10-20 · 28-08-2024 03:46PM

Good question… firstly a correction:

13 & 15: This is probably the feed from the attic tank to the cylinder (and not the cold riser) - you should be able to see where the plastic portion of that pipe routes to.

To turn off the warm water from the cylinder you would close off this tap and then leave the hot-tap running for a short time to stop the flow. No need to drain down the system. Also you might find inline valves on flex-pipes for isolating individual taps, but these aren't always fitted - probably for cost reasons!

carveone · 01-09-2024 09:20PM

Can I ask at what point the expansion vessel in the boiler itself is not considered enough? Is it after a certain number of radiators? I don't have one in my hotpress but then again I have 5 rads.

It's a great idea to know what everything does and be able to shut off valves. I always close gate valves by maybe one turn; I feel they are less likely to jam in that position. Like mine have done because they were opened fully and left for 10 years. Luckily of the two inline valves, only one is facing the wall and is thus inaccessible😒

As 10-10-20 says, it's fairly common here to skimp on putting in inline valves, although I believe you aren't allowed to any more. As he also says, you can cut off the hot by turning off the cold feed tl the cylinder. Assuming you can do so, because I can't!

10-10-20 · 01-09-2024 09:24PM

Yes, it's a sizing thing, but also some boilers don't have internal expansion vessels and need external ones.

Understanding the Hot Cylinder System

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