SANTON Unvented system draining

[da3533]

hey every one,
I have a SANTON unvented system model: TP150E.
I need to drain all the water as I need to change the lower heater element. However, I am only draining it using the drain valve at the bottom of the boiler. I can't get pressure to take out the rest of the water inside.
I think there's limescale blocking the drainer, not sure now.

I thought by letting the taps run, it will drain the water but there's gallons loads more but nothing from the taps.
Does this mean that the top part has been emptied and I need to drain the rest using the drainer?
If so, how and when does the water at the bottom ever be used via the taps?

 

[leakydave]

A DOC [drain off cock] should have been fitted on the cold feed pipe before it enters the lower part of the cylinder. It sounds like you have been draining your heating system which is an entirely different part to drain.

 

[da3533]

Thanks for your reply. I forgot to mention, it's an unvented electrical heating system and it's an apartment not house with no central heating.
There's a DOC attached to the bottom of the boiler that I need to use to drain the bottom of the boiler.
I need to drain the heating system in order to pull out and replace the heating element.
However, as for the heating element section located at the bottom, I loosened the and water started pouring out. So I can't change this element unless I get the water that it's in, out.

 

[leakydave]

By 'Boiler' do you mean 'Cylinder'? You will need to drain water out from the DOC and allow air to enter the cylinder from maybe a hot tap or by opening the TPRV on the side of the cylinder

 

[da3533]

Sorry I meant cylinder not boiler.
Ok thanks.
But how comes the water doesn't drain from the taps? I only emptied the top part of the cylinder via the taps and now I have to use the drainer for the bottom half. Is this half ever used by the taps if the top runs out of water or ?

 

[OwainDIYer]

That's an unvented hot water cylinder over 15 litres.

It should only be worked on by a plumber with an unvented hot water certificate.

 

[da3533]

Why do I need to? I'm only emptying the cylinder, the same way an owner would do in order to apply fernox ds-3 to remove limescale from the tank. This takes just, draining and filling . Do I need a specialist for this? Or..

 

[twgas]

Why do I need to? I'm only emptying the cylinder, the same way an owner would do in order to apply fernox ds-3 to remove limescale from the tank. This takes just, draining and filling . Do I need a specialist for this? Or..

With all due respect, you appear to have, virtually, no idea about your system so a pro would be the best advice.

 

[da3533]

Ok got it. It's just that, I have no money left for that. I just thought I could save money by emptying it and refilling.