CH system losing water

[osh]

First post on this forum and not a plumber by trade so apologies for the long ramble. I have a little technical knowledge so have a general understanding of CH sytems and can undertake basic maintentance on my own.

In Jan 2010 I had my old CH/hot water completely overhauled. I have a Vaillant Ecotek system boiler (on the 2nd floor) with a Heatrae Sadia Megaflo unvented mains fed indirect heated tank (on the first floor). The existing heating pipework for the ground and first floor was hardly touched (save for two new radiators installed on the ground floor), and seems to be in good condition throughout. At the same time we fitted a heated towel rail in the 2nd floor bathroom and Thermaskirt heating in the 2nd floor bedroom.

Last winter the automatic bypass Valve (Tower brand) failed. This was replaced with a different brand and at the same time an automatic air release valve was installed in the pipework near to the boiler.

Recently I have noticed that the CH system is losing water, noticeable in the towel rail as it is the highest radiator. I have bled it, and three weeks later it's at the same level. The most obvious answer is a leak in CH pipework, but I was hoping that there might be an alternative reason what could be causing it.

What I find strange is why the air in the system doesn't bleed out of the ARV, causing the system pressure to drop. Also, can anyone tell me what setting the ABV should be set to? At the moment it's at the lowest setting.

 

[dancinplumba]

hi, first post ? sez 5, anyway, was system flushed, filter installed and inhibitor added, does the air released smell? if so could be gas caused by rads corroding due to oxygen in ch water, otherwise most probs a leak, this could be on rad connections or pipework, Also your pressure release valve maybe passing. Does system pressure rise to red area on gauge ??
The position of arv will be to release air that has been through boiler. Setting of ABV will/should be set at resistance of system and set by installer. imho

 

[osh]

You're right, forgot about those post!!!

System was flushed at new installation (2010), inhibitor has been added twice, once at original installation and once at ABV/ARV installation. Not sure which filter you refer to...please clarify?
Air released has smell, but have always noticed that... Is this hydrogen, tested with a lit match?
Does anyone on this forum recommend the use of Fernox Leak Sealer for a problem such as this? Have heard arguments both ways.

Edit: If air is being introduced due to corrosion, would that not increase system pressure?

 

[dancinplumba]

to remove magnetic (which corrode also produce magnetite)/ non-magnetic particles from system, usually on return to boiler to prevent particles entering boiler.
yes test with match, if burns corrosion is till occuring.
you can use leak sealer, some say it clogs pump etc but i have used it and had no probs.
no as air can be compressed
imho

 

[osh]

Don't think filter was installed. I assume it would be somewhere in the near vicinty of the boiler, and haven't seen anything like that.
If corrosion is present, what's the best cure? Change radiators, or add more inhibitor?

Thanks for the help

 

[LeakFinder's]

Is the system pressurized if so what pressure are you setting it at? how long does it take to loss pressure?

 

[dancinplumba]

Don't think filter was installed. I assume it would be somewhere in the near vicinty of the boiler, and haven't seen anything like that.
If corrosion is present, what's the best cure? Change radiators, or add more inhibitor?

Thanks for the help

you can try more inhibitor yes and if still gasing up then good power flush and inhibitor
imo

 

[osh]

Holy swamoly. I tried the match test and expected a pop. What I got was a large light blue flame like a bunsen burner. I'm not kidding you. It gave me the fright of my life. Couldn't blow it out at first.
What have I got here?

 

[MattWeth]

Holy swamoly. I tried the match test and expected a pop. What I got was a large light blue flame like a bunsen burner. I'm not kidding you. It gave me the fright of my life. Couldn't blow it out at first.
What have I got here?

You've got hydrogen - a by product produced as the ferrous bits of your heating system corrode (the Oxygen in H2O combines with iron to produce iron oxide, liberating hydrogen).

So, you (probably) haven't got a leak and aren't losing water, you're gaining gas (hydrogen). In your position, I'd do a basic flush and refill using the correct amount of a good quality inhibitor.

 

[osh]

I've now spoken to the plumber that last worked on the system and installed the ARV. I challenged him as to whether it's possible his worker didn't top up the inhibitor to the correct levels and he says that even if inhibitor was correct, it could still introduce that much air over such a short period of time.
He says it's possible the ARV is introducing air, and I should disable it.
Does this make any sense?

 

[MattWeth]

I think the key is that you aren't getting air, you're getting hydrogen which is a corrosion by-product. There's no harm in isolating the AAV and seeing if it fixes the problem but my gut feeling is that it won't help.

 

[osh]

Is there a filling point on Vaillant Ecotec boilers? Seeing that the boiler is on the 2nd floor and I have no conventional radiators on that floor, the only way to introduce inhibitor would be to drain to 1st floor level.

 

[MattWeth]

Is there a filling point on Vaillant Ecotec boilers? Seeing that the boiler is on the 2nd floor and I have no conventional radiators on that floor, the only way to introduce inhibitor would be to drain to 1st floor level.

Use your vertical towel rad.

 

[osh]

In theory, yes. However, I have this towel rail, Warm Rooms LTD Ultraheat Portofino Towel Rail, which cleverly! has the valve underneath the top horizontal bar. I have once attempted to introduce inhibitor through there, but you cannot bend the tube round 90 degress, so that it doesn't spill all over the floor. Before you ask, the blanking cap is right up against a wall, so wouldn't be able to get through there. Would you recommend loosening the main wall connections?

How about via the filling loop?

 

[MattWeth]

You can use the filling loop but it will require at least a partial drain down. However as you should be flushing it anyway, this probably won't matter.

The good thing about using a rad is that you can just isolate it, siphon some water out and top up with inhibitor (but of course this might not be possible in your case).

 

[osh]

I will need a partial drain down anyway, as stated, due to the position of radiators. I am not going to do a flush at the moment, will leave till the summer.
I assume I disconnect the braided hose just after the filling tap?

 

[dancinplumba]

you should have two taps one on cold mains with check valve and tap on ch pipe, remove hose from cold mains side and connect to that,
use fernox express, dear but easy to use.
imo

 

[MattWeth]

If you're draining down, I'd just remove a bleed screw carrier or blank plug from a convenient (drained) rad and squirt the chemicals in there.

 

[osh]

Thanks everyone for your help

 

[osh]

you should have two taps one on cold mains with check valve and tap on ch pipe, remove hose from cold mains side and connect to that,
use fernox express, dear but easy to use.
imo

If I understand it correctly, using Fernox Express with the filling loop connector, does NOT require a drain down.
Can anyone guesstimate how many litres my system holds? I have a 3 floor extended house, 7 large radiators, 4 small radiators and a towel rail.
Is there a point in flushing with Fernox F3 Cleaner beforehand?

 

[dancinplumba]

if throu fill loop only need to release pressure down to zero,i would put in 2 tins to be on safe side.
yes its a good idea to flush with f3, leave in for a week
imho

 

[MattWeth]

Given the expense of a good inhibitor like Fernox, I'd at least do a basic drain and refill flush before adding the inhibitor (even better if you add a cleaner first) - it would be a right pain to throw it all away if you decide you really should have flushed after all...

 

[osh]

Thanks. I was intending to do that anyway. IIRC, it says in the Fernox instructions that you should drain, refill and drain until it runs clear, or something like that.

 

[osh]

Apologies for resurrecting this old post but have NOT done the drain down as above posts, yet and still having the air build up! Just trying to get my head round it all. Can someone explain why, when I get the air/gas build up in the towel rad, the system pressure will go up to 2 bar. When I bleed it, without letting any water escape, the pressure will drop down to 0.3 bar and I need to top up the system. However, at the previous bleed (before the build up) the pressure was set at 0.8-1 bar. So where has the 0.5-0.7 bar of water/pressure disappeared to? Surely if I bleed off the accumulated air it should reset back to where it was?

 

[Best]

You remove air - you create a space for the water to fill, so the water expands loosing some of it's pressure. Simple.

 

[osh]

I understand that. What I don't understand is why, after I bleed, it doesn't return to the original pressure that it was set at. It's as if some water has drained off somewhere.

 

[Best]

I understand that. What I don't understand is why, after I bleed, it doesn't return to the original pressure that it was set at. It's as if some water has drained off somewhere.

If the pressure drops, you have loss of water somewhere, slight or otherwise. Microscopic leaks from rad valves or brass joints are common leaks. A PRV will open & close & water will be lost if system pressure too high when boiler heats.

 

[MattWeth]

Assuming that the 'air' you have in your system isn't actually air but hydrogen (try lighting the gas that comes out of the bleed valve - you may be surprised!), then some water is being chemically turned into hydrogen and oxygen through the formation of oxides (rust). The hydrogen that's left is what you're bleeding out.

Also, microscopic leaks on the negative side of the pump can draw air in while not letting water leak out...

 

[osh]

Assuming that the 'air' you have in your system isn't actually air but hydrogen (try lighting the gas that comes out of the bleed valve - you may be surprised!), then some water is being chemically turned into hydrogen and oxygen through the formation of oxides (rust). The hydrogen that's left is what you're bleeding out.

Also, microscopic leaks on the negative side of the pump can draw air in while not letting water leak out...

That makes most sense. I did post earlier in the thread (a while back!) that the air was highly flammable, so we already know that it's hydrogen.

 

[osh]

Oh dear, seems that the system has sprung a leak overnight. Total loss of pressure.
Will need to flush out, and fill up with Fernox F1 and F4.
Can anyone tell me if there are any issues with putting them in together at the same time? Or is it as straightforward as it seems?

 

[MattWeth]

Check the expansion vessel (see if water is discharged from the schrader valve) and see if there is evidence of water at the relief valve discharge.

 

[osh]

I dont think I have an expansion vessel. Have a Megaflow. Are you talking about the open sided valve on the side of the Megaflow?

 

[Mike Jackson]

Oh dear, seems that the system has sprung a leak overnight. Total loss of pressure.
Will need to flush out, and fill up with Fernox F1 and F4.
Can anyone tell me if there are any issues with putting them in together at the same time? Or is it as straightforward as it seems?

I would initially top up with plain water and see if the pressure holds. Of it does try running the system and watch the pressure gauge, if it rises rapidly to above 3 bar your expansion vessel has lost it's charge pressure and will need re pressurising or replacing.

If the water pressure just drops rapidly you have a serious leak. F4 will not cope with a large leak so you will need to find the location of the leak. With the amount of corrosion that has been happening in your system a leak is quite likely.

Once you have discovered and resolved the problem of this larger water loss I would then deal with the corrosion issue. Just adding an inhibitor is unlikely to stop corrosion on this scale and the system needs a decent flush with F3 or similar before you add F1. Make sure you use the correct amount of inhibitor, one bottle is generally enough for 10 SINGLE radiators. Count double radiators as two.

 

[kay-jay]

good advice mike!

 

[osh]

In the end due to lack of time I just did a very basic flush (not very effective), and refilled with F1 and F4 last night. At 12.30 last night I left it at 1.1 bar and this morning at 6.00 the heating came on so it seems the pressure held overnight. Don't seem to have any problem with the pressure rising rapidly so I can only assume it is some sort of leak.
Are you saying that if I don't use F3, even with the correct amount of inhibitor, it will still corrode?
Does F3 need to be flushed out or can it be left in the system until the next flush? Don't fancy draining out £40 of product....