CH filter fitting

[GMM]

I know it's the wrong time of year to be thinking about disturbing a CH system but I may have no choice as I need to reorganise a radiator some time in the next couple of weeks.

It's a big system so when I drain it down I try to do as many things as I can to make sure I get the most out of the inhibitor. So, I've been thinking about putting a filter in. Without starting a heated argument about which is best (!), my current issue is where to put it. The best place would seem to be on the return to the boiler (I thought all the manufacturers specified this but looking them up online, it doesn't seem too clear-cut). Anyway, the return to my boiler is only brought together into a single pipe for about 6 inches, and that is hard up against a 10 foot ceiling, which would be a pain for access.

Siting on the boiler outlet is easy, as there's a few metres of pipe that's very accessible between the vent pipe and the pumps. Although intuitively this seems the wrong place, it seems to me that having a filter/trap after the boiler is better than not having one at all. Is there a flaw in this reasoning?

[fred]

In article , GMM writes

I suppose it depends on whether you are happy to use your boiler heat exchanger as a pre-filter to your purpose built filter device :-)

Yes, it is a semi-comical response but it is a realistic assessment of what you are planning.

If you have an old boiler with waterways the size of the M1 then it may be of little consequence but if you have (or plan to have) eg. a Worcester Bosch Compact model installed then you'll be sorry as any loose scale will be trapped by the 300quid heat exchanger rather than the easily cleared filter. This would be of particular risk if you were to attempt percussive descaling of the system radiators which is a common method on boiler replacement.

Is there any opportunity to re-route the boiler return to create either a lower route or one capable of providing some horizontal space to accommodate the filter? That would certainly be my preferred choice.

[Roger Mills]

You could always use multiple filters - one in each return leg before they combine - if this is easier!

[harryagain]

The main reason these filters have suddely become so popular is the advent of boilers with aluminium heat exchangers. They are usually have magnetic traps as well as filters. Some are also useful for getting inhibitor into the system. New boilers have very narrow waterways, easily blocked. Crud in the boiler can cause local hot spots and with aluminium, the metal can burn away. Rust particles in an aluminium boiler are disastrous, all sorts of galvanic effects are set up.

So the filter should go on the inlet/return side of the boiler as close as possible.

They are often installed to protect a new/replacement boiler in an old system.

Good idea to clean the system out if you have a big job on it.

The best way is to take out radiators and hose them through outside in the garden. However, sometimes pinhole leaks then become apparent.

[GMM]

Well, that was my initial view, which prompted the question, but is it worse than not having a filter at all if there is no opportunity to site one in the ideal position?

Unless I were to radically change the boiler position (which is very high but fitted before my time in the house), I don't see much prospect of that, and certainly not in the time frame relevant to this. TBH, if I was going to that much trouble, I may as well replace everything to generate a system much more of my choosing. Cost aside, however, I certainly wouldn't start down that road at this time of year.

[GMM]

I had thought of that but the individual legs are no more accessible. Could always have a filter on every radiator....

[Chris French]

I think it is better there than not at all.

I considered this last year when doing some system mods. But didn't bother in the end.

Boiler with a big old cast iron heat exchanger, some black water comes out of rads when drained, but nothing that affecting performnace. Water circulating was clear.

So decided there wasn't any real need for it, and fitting for me would have been a bit awkward. Plumped for running some x400 cleaner through and new inhibitor. If we ever get a new boiler fitted I would put oen in though

[fred]

With certainly better than without.

Understood but since the boiler is high, is there not an opportunity to modify the return to bring it lower and add the filter to that loop? Any resulting mess could be boxed in. Difficult to fully understand w/o a pic.

[John Rumm]

What kind of boiler?

The flaw is that if the boiler is a modern condensor with narrow water pathways, anything large enough to be damaging may get trapped by the boiler before it can get to the filter.

So I would try and stick it in the return even if you have to extended the pipe down to the filter and back again to the ceiling to do it.

[GMM]

It's (actually they are, as there are 2) and Ideal Icos which, being a condenser, is probably in that category. I had rather assumed the majority of stuf caught would be fine magnetite but I'm sure there's a good chance of dislodging other crud when hacking about with rads etc.

I had rather discounted bringing the pipework down as it could generate an ideal air trap, which wouldn't help things much. I had rather hoped to fit something relatively quickly, so if I have to do any significant surgery I'll probably leave it until the summer, just in case anything goes wrong (Sod' Law often being proven in these cases).

From what I've seen, most of the filters require some access from the top and the only one that doesn't is the Spirotrap which. Although it's attractive because it looks robust, it gets poor reviews for its ability to trap anything, which is a fairly central property for a filter.

[johnjessop46]

I'd agree with looping down to install a filter. Use a tee with a manual air vent to deal with the potential air trap.

[fred]

In article , [e-mail] writes

How can a U with the bend at the bottom trap air?

[GMM]

Not in the U-bend but adjacent to it. The pipe runs horzontally then turns down via an elbow into the top of the boiler. Introducing a U bend before this would mean the remaining part of this horizontal would make a high point and, since it's up against the ceiling, there would be no space for a bleed valve to vent it. Beats me why they installed it like this: The base of the boiler is at head level or more, although there's nothing beneath it to prevent a lower installation. A shorter person would need steps to reach the control panel. Re-mounting it a foot lower would solve the current problem but that's almost as much work (and opportunity for issues to arise) as fitting it from scratch, so I'm disinclined to do that in a hurry.