The Lemon Fool

Is it sufficient if I just add inhibitor to the expansion tank - will the expansion/contraction draw the inhibitor into the central heating system?

It's always worked for me. But it may take a few weeks to get right round the system.

BJ

It's dead easy to drain off a little from the central heating system so that the inhibitor you are adding is pumped around the system straight away. Most modern radiators have drain cocks......just attach a short length of hose and drain off a couple of bucket loads of fluid before adding inhibitor to the the expansion tank.

Why wouldn't you drain off some before adding inhibitor ?

richlist wrote:It's dead easy to drain off a little from the central heating system so that the inhibitor you are adding is pumped around the system straight away. Most modern radiators have drain cocks......just attach a short length of hose and drain off a couple of bucket loads of fluid before adding inhibitor to the the expansion tank.

Why wouldn't you drain off some before adding inhibitor ?

Usually there is only one drain cock in the system at the lowest point (so look downstairs first), on a radiator which isn't using microbore piping connected to a manifold (so look for a radiator with 15mm piping).

I would isolate/tie up the ballcock before starting the exercise, then add inhibitor followed by turning the supply on/untying the ballcock.

For those of you with a downstairs backboiler, your drain cock is almost certainly located next to the boiler as that is almost certainly the lowest point of the whole system.

Inhibitor is introduced to the system quicker, if a small amount of water is first drawn off the system. One way I've done this in the past, is to drain enough to empty the f/e tank, and then another bucket full. Then if you tip in the inhibitor it will be easily mixed.

The one big issue with draining off a bit first is as follows......

If you have an oldish setup, and you lack experience, it's possible that you can loosen off a drain cock, do your work etc. only to discover that the drain cock then drips after retightening. Sometimes the drip stops after a day or so (put a bowl under it for a few days etc..), but sometimes it goes on. Our house is quite old, and has had shoddy maintenance in the past. As a result a few years back...I ended up changing out a bunch of these old draincocks because of this kind of annoyance. One thing one might consider is to at least buy a replacement draincock....just to obtain the correct sized washer (which is the usual culprit for any subsequent drips), so that you maybe able to cure any possible subsequent leaks without needing to replace the draincock itself.

HTH, Matt

richlist wrote:It's dead easy to drain off a little from the central heating system so that the inhibitor you are adding is pumped around the system straight away. Most modern radiators have drain cocks......just attach a short length of hose and drain off a couple of bucket loads of fluid before adding inhibitor to the the expansion tank.

Fair point, richlist, I forgot to mention that. But then, if I'm already going to be up in the loft, it's no particular problem just to take a couple of empty lemonade bottles up there, dunk them in the tank to fill them, and then pour (all but one of them) back into the tank once the inhibitor's in. Easier than faffing about with a draincock downstairs.

Having said that, the draincock approach might help you to eliminate a bit of sludge or dirt, which is never a bad thing. And yes, draining down enough water to empty your header tank and then a few gallons more does indeed get the inhibitor into your system straight away, rather than waiting for it to mix naturally.

If I'm feeling really virtuous, I might take the opportunity to clean the inside of the header tank while it's empty, and to check the state of the tank cistern valve. At this time of year, though, my main priority is to get out of the freezing cold loft as soon as possible.

BJ

I second the point about the drain cock not resealing. Have some spare washers as an absolute minimum. The old washers can be quite perished and may not reseal.

You may find that the drain cocks are outside. They may just poke through an outside wall or they may be behind an aluminium cover in the wall.

Julian F. G. W.

I have a piece of stiff wire (untwisted coat-hanger) sitting on the polystyrene cover of the tank.

When I need to add stuff I put the wire under the ballcock arm to stop it dropping and have a plastic bucket and jug in the loft with me.
I ladle about 3 times the volume of the stuff to be added out of the tank into the bucket, pour the stuff in and remover the wire so that the water mixes it in well.

If the system was kettleing, it stops within a couple of hours of adding inhibitor and the other stuff.

Slarti

To broaden the topic slightly, what about a closed system? Our pressurised system has been untouched for nine years now. Is there a rule of thumb about when to replace the circulating water/inhibitor, or do you just need to inspect the mixture and see how black it is? If replacing, how do you get the inhibitor in?

You fill the system via a radiator. See here for the necessary kit (and instruction manual)
https://www.screwfix.com/p/flomasta-uni ... lsrc=aw.ds

Drain-cocks that have not been opened for ages often jam: no water comes out because the washer has stuck to the seat. When this happens:

- wait for the system to cool down
- attach a drain hose to the cock (use a Jubilee clip to stop it being accidentally nudged off)
- put a shallow drain pan under the cock
- unscrew the square-headed cock valve until it comes out completely
- the washer will now be exposed; gently prod it until it moves and water gushes out, then quickly block with your thumb followed by a small cork
- the water will now drain via the hose

Sounds dodgy but works!

Parky wrote:To broaden the topic slightly, what about a closed system? Our pressurised system has been untouched for nine years now. Is there a rule of thumb about when to replace the circulating water/inhibitor, or do you just need to inspect the mixture and see how black it is? If replacing, how do you get the inhibitor in?

You squirt it in,

https://www.screwfix.com/p/sentinel-x10 ... 00ml/5058v

Fernox do a similar one.

Julian F. G. W.

Parky wrote:
To broaden the topic slightly, what about a closed system?

Our pressurised system has been untouched for nine years now. Is there a rule of thumb about when to replace the circulating water/inhibitor, or do you just need to inspect the mixture and see how black it is? If replacing, how do you get the inhibitor in?

I think these types of central-heating system filters are popular both during new-installs and as retro-fit to existing systems -

https://www.screwfix.com/p/fernox-tf1-total-filter-22mm/84311

Whilst the primary function of these filters is to capture the gunk as it travels round the system, you'll notice that they also have isolation-valves either side of the filter, with a drain-down valve at the bottom of the filter itself.

What this means is that as well as being used for cleaning existing gunk out of the system, these filters can also be isolated, drained, cleaned, and then filled with inhibitor, with the relevant valves then re-opened to introduce the inhibitor into the main heating circuit.

Whilst a part drain-down of a radiator can of course be used for this process, the above use of an existing filter can often be a neater one if it's an option.

Cheers,

Itsallaguess

Itsallaguess wrote:I think these types of central-heating system filters are popular both during new-installs and as retro-fit to existing systems -

https://www.screwfix.com/p/fernox-tf1-total-filter-22mm/84311

Whilst the primary function of these filters is to capture the gunk as it travels round the system, you'll notice that they also have isolation-valves either side of the filter, with a drain-down valve at the bottom of the filter itself.

What this means is that as well as being used for cleaning existing gunk out of the system, these filters can also be isolated, drained, cleaned, and then filled with inhibitor, with the relevant valves then re-opened to introduce the inhibitor into the main heating circuit.

Whilst a part drain-down of a radiator can of course be used for this process, the above use of an existing filter can often be a neater one if it's an option.

Cheers,

Itsallaguess

This Fernox Omega version is all metal and should overcome leakage issues due to the heating and cooling of the plastic parts on the older type - even a 25-year warranty.

https://fernox.com/product/tf1-omega-filter/

Itsallaguess wrote:

Parky wrote:
To broaden the topic slightly, what about a closed system?

Our pressurised system has been untouched for nine years now. Is there a rule of thumb about when to replace the circulating water/inhibitor, or do you just need to inspect the mixture and see how black it is? If replacing, how do you get the inhibitor in?

I think these types of central-heating system filters are popular both during new-installs and as retro-fit to existing systems -

https://www.screwfix.com/p/fernox-tf1-total-filter-22mm/84311

Whilst the primary function of these filters is to capture the gunk as it travels round the system, you'll notice that they also have isolation-valves either side of the filter, with a drain-down valve at the bottom of the filter itself.

What this means is that as well as being used for cleaning existing gunk out of the system, these filters can also be isolated, drained, cleaned, and then filled with inhibitor, with the relevant valves then re-opened to introduce the inhibitor into the main heating circuit.

Whilst a part drain-down of a radiator can of course be used for this process, the above use of an existing filter can often be a neater one if it's an option.

Cheers,

Itsallaguess

Yeah we have one of these. It gets a clean out annually along with the boiler service.

Still I'm glad this thread has come along....it's a reminder to tip a bottle of fernox into our system. I usually try to do this every couple of years.

Matt

TheMotorcycleBoy wrote:Still I'm glad this thread has come along....it's a reminder to tip a bottle of fernox into our system. I usually try to do this every couple of years.

Matt

Are you saying the inhibitor loses its effectiveness after a couple of years, and should be topped up? I haven't seen that anywhere else. I would have expected it to last much longer in a closed system.

TheMotorcycleBoy wrote:

Yeah we have one of these. It gets a clean out annually along with the boiler service.

Still I'm glad this thread has come along....it's a reminder to tip a bottle of fernox into our system. I usually try to do this every couple of years.

Matt

It is possible to over dose the system which can cause problems particularly with the pump.

I've been renovating our house which involves draining down and refilling radiators as we work through the rooms. When we had the boiler serviced I asked if we should top up the inhibitor but he recommended that we left it until later because of potential over dosing. We've now done all the central heating drain downs and the system got re dosed a couple of months ago.

I'm sure someone will know more about this. The warning is based on hearsay only rather than personal experience.

sg31 wrote:I've been renovating our house which involves draining down and refilling radiators as we work through the rooms. When we had the boiler serviced I asked if we should top up the inhibitor but he recommended that we left it until later because of potential over dosing. We've now done all the central heating drain downs and the system got re dosed a couple of months ago.

I'm sure someone will know more about this. The warning is based on hearsay only rather than personal experience.

Our plumber said if we were only draining/refilling a couple of radiators for decorating then not to worry about inhibitor, but much more than that we should re-dose when we finish the last one.

This is in Scotland with soft water.

Scott.

sg31 wrote:

TheMotorcycleBoy wrote:

Yeah we have one of these. It gets a clean out annually along with the boiler service.

Still I'm glad this thread has come along....it's a reminder to tip a bottle of fernox into our system. I usually try to do this every couple of years.

Matt

It is possible to over dose the system which can cause problems particularly with the pump.

I've been renovating our house which involves draining down and refilling radiators as we work through the rooms. When we had the boiler serviced I asked if we should top up the inhibitor but he recommended that we left it until later because of potential over dosing. We've now done all the central heating drain downs and the system got re dosed a couple of months ago.

I'm sure someone will know more about this. The warning is based on hearsay only rather than personal experience.

I don't think this is correct. If you read the Fernox FAQS they say the following.

Can I overdose with Fernox Protector F1 or Filter Fluid+ Protector?
No, overdosing is not detrimental to the system. It is important to ensure that sufficient Protector is present in the system.

https://fernox.com/cpt_faqs/

I checked because I have always added more Fernox to our system to be on the safe side!

And the method I used to get it into the system is to use a heated towel rail, as shown in the video below.

https://www.youtube.com/watch?v=WouU0IKre30

This method was recommended to me because otherwise in a system with no leaks the inhibitor can stay in the header tank and not circulate at all.

Hope these comments are helpful.

Howard

I don't think that you can overdose with the inhibitor you add. I personally have not had a pump issue after 20 years of DIY plumbing.

After seeing just how bad poorly maintained systems can be (e.g. the house we've been in for the last 6 years, has 14 radiators and was constructed in the early 1950s, yes frightening potential gas bills, hence use of a (freely sourced wood) log burner as well), I would always go for too much rather too little fernox.

4 years back when I changed out a bunch of old rads, and upgraded the boiler, disposed of the concrete (probably an asbestos-based composite, think of cattle water troughs back in the day!!) f/e tank, I recall scooping actual flakes/chunks of ferric oxide from the bottom the tank mentioned. Yes in addition to the usual "sludge" there was granular oxide (say 3 mm flakes) which I can only assume came the internals of rads gradually flaking off.

I personally would not listen to any plumber who recommends not adding some more inhibitor, even if you've "only had a couple of rads off the wall". But that's just me - I'm somewhat stubborn at times!!

Matt