HELP pls - boiler low on pressure - not sure how to refill?

Goodadvice75

Hi,

We have a "Vaillant ecoTEC Plus 831" gas combi boiler.

The pressure gauge is showing way lower than it should according to the manual. The manual says we need to "fill the system with water before putting the boiler into operation" - but it doesn't tell us how to do this?!?!

Please can anyone help?

Have had the boiler a few years and know we should have been checking the pressure levels but just happened to notice the gauge was low today - now worried about switching it on!!

There are four or five copper pipes underneath it, one of them has a check valve type of thing on it, the one that has the slot for a screwdriver to turn it on/off - is it this one we need to open does anyone know? (This also has a "magnetic scale inhibitor" attached to it, so am guessing this is the cold water in, but not sure).

There is also a sort of flexible silver pipe which is attached in a loop and this has a knob to turn at either end - not sure if it's this we should be turning instead, and if so which side!

Sorry, in a complete state of confusion here! Wish the manual told us what to do... Don't want to turn touch a gas pipe by mistake...!

Thx for any help.

Myser

What you are looking for is a filling loop. Depending on how your boiler has been installed, it will either be under the boiler and you can refill your system using a special key or a separate loop which connects to the main cold water supply.

Does the silver pipe look like this:

http://www.toolstation.com/images/library/stock/webbig/35419.jpg

If so, that is the filling loop.

Opening the black lever will allow cold water into the system. In your case, it seems you have two valves which is a double check valve filling loop. The other valve may be a screw-type rather than a lever. It is possible that this one may have already been left open previously by the person who last filled the system. In any case, both valves will need to be opened to fill the system. Monitor the gauge and make sure that it does not go above the green zone. Fill the system slowly as it can easily overshoot.

A system should not be over or under pressurised. Modern boilers should cut out if under or over pressure.

Once you have finished filling the system, you should shut both valves. This is to prevent contamination to the clean water supply - hence a double check valve. You are actually supposed to also disconnect the pipe to avoid any contamination but most people leave it connected.

Goodadvice75

Hi Myser,

Thanks so much for your quick reply.

yes, the pipe you link to looks the same as the one we have, except ours has the knobs on each end of the pipe. At one end there is still the knob even though at the very end it is sort of capped off (hard to describe). Then at the other end there is a knob just like the black one in your picture.

Worried may do doing something wrong and blow the house up....

So pls can I just check that we turn both of these knobs which are attached to the silver pipe on (not sure which way they turn but perhaps they will only turn one way - at the moment they both say "closed").

Does it matter which knob we turn on first (the left one is the capped off one, the right isn't capped)?

Then just watch the gauge as it fills and turn both off when it's got to 1.5 to 2 (this is what the manual says)?

Thx again.

Myser

I would suggest opening the one nearest the double-check valve first - In the pictures in both links below, this is the valve on the left. Then open the other one.

http://www.toolstation.com/images/library/stock/webbig/83963.jpg

http://www.plumbingsuppliesandfittings.co.uk/admin/images/15583_FillingLoopHose201109.jpg

Hope this helps.

If the system is completely empty, you should also add some inhibitor to the system to stop corrosion of the radiators. This can be done with a DIY kit from hardware or plumbing stores and is easier to add when the system is empty before filling it.

You add it via one of the radiators or your installer may have provided a point near the filling loop to do this.

http://www.plumbworld.co.uk/images/pwsl0001roomshot.jpg

ormus

my vaillant pro 24 has a filling loop similar to this one.
but with a lever at both ends.
open both taps, watch the pressure guage reach approx 1.5 bar, then shut both taps off.

Goodadvice75

Hi Myser and Ormus,

Thank you both. Really I wanted to "beam" one of you here to do it for me (so nervous of anything to do with gas) .... but have washing to dry and am freezing so plucked up courage.

Tried one tap on it's own and there was no whooshing/filling noise, so went for both and it started whooshing and the gauge is now back up to a good level.

Heating on, very happy!

Thank you so much for your help and reassurance!!

:j

PS. Myser, thanks for the advice re inhibitor - I'm hoping it wasn't completely empty as we've had the heating on in the last few days without any problems, it was just that I noticed the gauge down low and went into panic mode.... fingers crossed it will all be okay now.

Myser

A couple of things to note - do you remember the last time the system was repressurised. If it wasn't very long ago, you may have a small leak somewhere in the system. Usually this can be around the radiator valves or perhaps a radiator bleed screw hasn't been closed properly when bleeding.

The other thing is that when water is heated, it expands so you may see the pressure on the gauge fluctuate. Hence why you shouldn't fill the system into the red zone.

Goodadvice75

Thank you Myser.

I can't honestly remember the last time it was done - I know we had an issue with a heated towel rail not heating up properly and the guy that fixed that also topped up the pressure but this must be almost a year ago.

Thank you for the advice though, I will check around all the radiators to see if there are any obvious signs of a leak anywhere.

Thanks too for the advice re the pressure gauge, I only filled it to about less than a quarter, still well within the "light grey zone" the manual mentions.

Even so, I'm sure I won't be able to stop myself checking it for the rest of the evening, worry monger that I am...!

Goodadvice75

Actually.... just taken a peek and the gauge has moved up quite a bit now the boiler is on.... eek!! Should/can I release some of the pressure some how? What will happen if I've over done the pressure...?!?

Myser

I would suggest checking all the bleed screws on all the radiators including the towel radiator one are tight.

We had a similar problem with our towel radiator due to the thread on the valve not being fitted tightly enough. The problem is, if the leak is small you won't notice it as the water evapourates as the radiator heats up.

It can also be caused by old leaking valves too.

If the pipes to your radiators are copper, you may notice green marks along it if water is leaking from the valve.

Myser

Don't worry about the over-pressure. It is normal for the pressure to rise slightly when boilers heat up.

If the pressure reaches a dangerous level, the pressure relief valve in the boiler will open and automatically drain water from the system.

No need to worry - so long as you have shut both filling loop valves!

Edit: I just read your previous post - it is normal for the pressure to drop slightly over the course of a year.