Steel K rads vs Aluminum rads

nygeminigal

The plumber has notified me that I need to flush out my whole radiator system and actually replace two rads also. He suggested I replace the rads with same...well newer versions of same steel k rads. I was looking into upgrading to aluminum rads but it seems I won't get much benefit because 1) I am only replacing two and not all the rads. I was also told that 2) since the alum rads don't come in the exact same size as the k rads that some retrofitting (lifting up floors or running pipes along the skirting) may have to be done. Also told that 3) since I'm only replacing two rads that if I put in alum rads they would get contaminated by any sludge that didn't get flushed out from the old rads therefore needing to replace them again in 3/4 yrs.

Based on the above I am leaning towards just replacing the rads with similar steel k rads (I hear they are more efficient now 5 litres / meter vs my old 7 litres / meter) even though I would prefer to upgrade to alum rads.

Would appreciate confirmation that the above 3 items are true and advice on what you would do.

BTW - anyone know how sludge gets into rads in the first place and how can this be prevented going forward?

Thanks.

antoinolachtnai

First, if you need to replace two of the rads, you will probably need to replace the other rads at some stage in the future too. Not necessarily, but good chance.

If you ask me, aluminium rads are the way to go. The retrofitting isn't really that bad, if you ask me provided there is no big problem getting access to the pipes, because it can be done with plastic pipes (providing you don't have an aesthetic problem with that). But it all does take time and effort. It is also an opportunity to move radiators to a more convenient location, or maybe use a tall 'vertical' radiator if it suits your space better.

litres per meter isn't really a measure of efficiency of a radiator! It might be vaguely related, but it's not a straightforward relationship. What matters with a radiator is the output. This is measured in BTU (old imperial style) or in kilowatts (kW) more modern. Sizing radiators is all very complicated, and you should listen to your plumber's advice. The important thing these days seems to me to be to make sure you have a bit too much rather than too little.

Here is my understanding of where sludge comes from: new water goes into the system, or bubbles up to the roof tank. It has oxygen in it. Oxygen + Water + Steel (but also copper) = rust. This is the problem. The way you deal with it is by having less oxygen in the system by 'sealing' the system, so there is no longer a roof tank, by making sure there are no leaks (which eventually results in drawing more fresh water into the system when it is topped up) and by replacing steel radiators with aluminium. You can (and should) also put in an additive which inhibits the rusting.

The sludge then sort of washes around the system as the water is pumped around and lodges anywhere handy (like in the bottom of radiators).

The plumbers will be able to give more detail on this.