Hi all, I want to install a phosphate doser into my new central heating system (to reduce combi-boiler maintenance costs). Can anyone recommend one that is inexpensive, and which will probably be cheap to refill for years to come?
Many thanks,
A
I had to make a similar decision recently, and in the end went for:
John Rumm wrote in news: snipped-for-privacy@brightview.co.uk:
Thanks for the tip. Do you have to buy a 'cartridge' for that model, when it runs out? I had a vague idea that some phosphate dosers can be refilled with generic phosphate balls (which would be useful if the cartridge-maker goes bust).
A
Yup that one takes a cartridge.
Some like the Combimate, take balls loose. But having had one of those in the past I was less impressed with it. (more of a hassle to top up, restricted flow a bit more, and rattled a tad in use). They are also quite pricey.
There is a moderate chance you could refill one of the BWS cartridges if needs be.
Why not get a water softener and all you need then is salt?
harry wrote in news:56002e72-ef88-4af1-bac1- snipped-for-privacy@o30g2000vbu.googlegroups.com:
That's an idea; thanks. I've just been searching for a conversation I had about this subject a few years ago, and there was a heated (and inconclusive) debate about whether phosphate dosers and water softeners were more effective than ion exchange water softeners. No-one involved in the discussion could point to any controlled tests to back up their opinions. Anyone got any educated (or fist-hand experience) opinions on this question?
In a previous house, I installed a phosphate doser, thinking it would prevent my heat exchanger from scaling up. One year later my boiler's heat exchanger was clogged again, as it had done almost every year previously. Having said that, I think it was partly clogged with iron oxide (i.e., black rust). Perhaps water softeners don't inhibit the formation of iron oxide. Is there anything that inhibits the formation of iron oxide, as well as limescale, in heat exchangers (apart from things like Fernox, which obviously can't be added to mains drinking water.
A
A phosphate dosing unit won't soften the water. It will stop the scale precipitation out when its heated, but let the water dry on a surface and it will still leave marks etc.
It could clog with iron oxide on the primary side of the HE. There should be none in the HW side. But that would be a separate problem caused by corrosion in the heating system.
The primary side, can be dosed with inhibitor like Fernox - you will not be drinking that. The HW side of the exchanger can be protected from scale by the phosphate unit. Unless there is something odd about your local water supply, there should be no iron oxide in that. If that is proving to be a problem then you need a particulate filter on the cold supply (BWS do a matching unit with a cartridge for that - you can get them as a pair from SF)
John Rumm wrote in news: snipped-for-privacy@brightview.co.uk:
John, Thanks for the clarification. Thinking back, I think my hot water taps were delivering luke warm water, which, as you point out, suggests it was the primary side that got blocked with the iron oxide, thus stopping the heat getting to the tapwater.
Yes, now that you've helped to clarify that, I see that my phospate doser would not have been responsible for that.
So the only real question now seems to be whether to install a phosphate doser, a salt-filled water softener or an ion-exchange water softener.
You seem to favour phosphate dosers, yes?
Regards, A
Well you could have poor heat transfer from primary to secondary sides of the HE because the primary side was blocked by black iron crud, or the secondary side was furred up with limescale[1]. So you can get a similar symptom from two different problems with different causes and solutions.
[1] You may also get reduced flow rate from that as well, but since most common combis can't heat big flow rates in the first place, you are probably less likely to notice that in real life."salt-filled water softener" and ion exchange are one and the same thing IIUC. The salt is used to make a brine solution that is used to flush and "charge" a resin matrix with sodium ions. The fresh water then passes through the matrix where the calcium/magnesium etc ions in the water are attracted to the matrix, and the sodium ions in it are attracted to the water. Hence one set of ions gets swapped for another. (and contrary to popular expectation, the salt is not not added to the domestic water - its just used for the flushing process)
Favour would be the wrong word - they do different things (well one is a reasonable subset of the others).
There is also a big difference in installation cost (although you may find the effects of a real softener will eventually pay for themselves in reduced detergent use etc).
Whether you want to go for fully softened water will depend a bit on what you want to achieve and why. Some folks are not keen on soft water, anyway - although if you are softening a naturally hard supply, then at least you have the option of using it "raw" as well for drinking etc.
John Rumm wrote in news: snipped-for-privacy@brightview.co.uk:
Many thanks for your help. Yes, I am in a *very* hard water area. My primary reason for wanting softened water is just to stop the heat achangers furring up. Saving money on detergents, shampoo, etc., certainly sounds appealling.
A
Soft will do that. On the down side, it can be its harder to rinse, and can be a bit more aggressive on plumbing fittings in other ways. They waste a certain amount of water in the recharge cycle, and you need to remember to fill them up. Depending on the type you go for (one tank or two) you may also get moments where it can't keep up with delivery from the prepared softened water. Lastly they fill a reasonable amount of space, so you need somewhere to site one. So if going that route, read up on the types and features before making a decision.
John Rumm wrote in news: snipped-for-privacy@brightview.co.uk:
I will do that. Thanks again! A
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