Only one Storage Tank ????

[highliner]

Hi,

Can someone please explain to me why I have only one tank in the loft. I thought there was always a second smaller F E tank that supplies the rads. It appears the one tank in my loft supplies both the taps & the central heating via the cylinder in the airing cupboard. Is this right ?

Appreciate any comments.

Ta

 

[rpm]

All depends on the system, perhaps yours is a sealed system so no expansion tank required.

 

[Aquarius]

As per @rpm, sounds like you have a sealed system, unless you have a combination cylinder? What type of boiler do you have? Is there a pressure gauge anywhere?

 

[SJB060685]

I have known combined tanks in the past, although this obviously has the risk of cross contamination.
Another possibility is you have a primatic cylinder where both systems use the same header tank, although under normal operation the two systems are separated by an air bubble within the cylinder.

 

[highliner]

I have a condensing boiler (ideal logic s24IE) which has a pressure gauge on it sitting around the 1 bar mark.

I'm looking to replace a couple of rad valves in the kitchen but confused as to where the best place to isolate the supply before draining down.

 

[SJB060685]

You have a sealed system then, so no F&E for heating system in the loft

 

[highliner]

Ok thanks. So I can just isolate the supply that goes to the bottom of the hot cylinder from the loft & drain from there?

 

[SJB060685]

Ok thanks. So I can just isolate the supply that goes to the bottom of the hot cylinder from the loft & drain from there?

No that would be the cold fill from storage tank to the cylinder and is not the point to drain down from as its for the HW cylinder.
You need to find a drain off on the boiler system side and attach a hose and open up the drain off and then open an upstairs radiator bleed point to allow air in to help push the water out.

 

[king of pipes]

As above you need to drain the water from the radiator circuit on a sealed system this is filled and drained manually usually Via a braided hose called a filling loop below or near the boiler kop.

 

[highliner]

I have no drain off point. (apart from on the boiler but that is higher than all the downstairs rads) I'll just connect a hose to the lowest rad. So I really need to tie up the ball valve & empty the storage tank in the loft?

 

[SJB060685]

I have no drain off point. (apart from on the boiler but that is higher than all the downstairs rads) I'll just connect a hose to the lowest rad. So I really need to tie up the ball valve & empty the storage tank in the loft?

No the header tank with ball valve in the loft is for hot water system. Your heating system should be filled via a filling loop

 

[king of pipes]

No you don't the circuits are separated the tank in the loft only fills the cylinder when you use domestic hot water, the heating circuit is filled manually via a filling loop off the cold water main, so as you described isolate the lowest radiator and drain into a vessel of some description, then remove attach a hose one of the rad valves and drain the heating via that open the air vent on the upstairs rads first and on the downstairs as the water level drops . Kop

 

[highliner]

I thought the tank supplies both circuits. After replacing a rad before the system automatically filled back up.

 

[John.g]

Its possible but highly unlikely that the tank supplies both systems with a non return valve in the supply to your boiler system to give you a (semi) sealed system.
If the boiler pressure gauge is higher than 0.4/0.5 bar when COLD then you will definitely have a filling loop somewhere.
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Another check would be to ensure the header tank full with no draw off then drain off say 5 litres from that bottom rad and if the ball cock starts making up then you know that the system is fed from that header tank.

 

[highliner]

The boiler pressure is around 0.2 Bar at the moment cold. I've just fitted a towel rail, so I'll fill it & watch the storage tank. Afterwards, for this kind of system, I presume the best way to put inhibitor back into the system is directly into a rad/towel rail ?

 

[John.g]

Using the towel rad should be fine.

 

[highliner]

I've just opened the valves for the newly installed towel rail in the bathroom. The rail auto filled ok & the loft header tank did start to drop & replenish. So the one tank definitely does feed both the taps & rads.

I still have to replace valves on a kitchen rad...

• Do i have to isolate the tank before draining down or is there a valve down stream like in the airing cupboard ?
• If i drain from the tank is there a chance I could introduce air locks or other problems to the hot cylinder etc ?

Thanks for the replies

 

[John.g]

There may be a isolating valve, have a good look at your storage tank, it may only have one feed out that supplies your HW cylinder + maybe upstairs toilet & wash basin or it may have two separate ones, the outlet(s) just may have isolation valves which you can shut. I'd say its more than likely that you may find a tee off from the CW supply to the HW cylinder into the coil, in the airing cupboard, this section of pipe may have a NR valve in it and also a isol valve.
You may just have to drain down the storage tank, if so refill it very slowly.

What was the boiler cold pressure after refilling?.

 

[SJB060685]

Does the header tank have two vents rising above it?

 

[highliner]

I may have found it. The red manual valve below the mains in...

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Here is the front view. 3 outs going to the airing cupboard & an open ended pipe hanging into the top

view... the tank has 3 outs going to the airing cupboard & another open ended pipe hanging into the tank

 

[John.g]

That looks like it, especially if its 1/2"?.. the pipe hanging over the top will be the vent from the top of the hot water cylinder.

 

[highliner]

It was actually a 3/4" pipe & not connected to the heating system. Looks like it goes to the en-suite shower. Through a bit of elimination, I managed to find the isolation valve for the rads & it was in the airing cupboard.... it T's off from the header tank supply to the hot cylinder. Also looks what I think is a non-return valve directly below it.

Job done. Thanks all for the replies