# BWT Mg2 Filters?



## jonbutler88 (Dec 31, 2015)

Hi All,

I've been trying desperately for a while to not dip my toe into trying to mix bottled waters for the "ideal" brew, and instead settled on using Waitrose Essential with my Aeropress. However, I've just received a Kalita Wave, and after working out how many bottles I'll go through a week it's time to consider alternatives to bottled. While chatting to Chris from Has Bean, he mentioned that tap water put through a BWT Mg2 filter is pretty good, so I wondered if anyone here uses these and can shed some light on how good they are for pour over brewing? I've seen it mentioned in a couple of the other water-related threads but no indication of if it's any good...

To pre-empt some responses, I suspect it will depend a lot on the tap water I'm starting with before filtering... Does anyone have recommendations for a kit to test the current properties of my tap water to get an idea of what needs to be tweaked?

Cheers,

Jon


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## Step21 (Oct 2, 2014)

I use one for filtering tap water for drinking and making tea. Doesn't make great coffee for me. I haven't tested my tap water so don't know what i've got to begin with. Bottled water is much better if you know what to look for/blend. Waitrose Ess is decent.

Remember to factor in the cost of the filters and that they become less efficient as time goes on - you are not getting identical filtration on Day 1 as Day 30.

If you want to test your water you'll need a TDS meter and need to measure General Hardness and Carbonate Hardness (various kits available from aqua marine shops). Ideally you'll want to know Calcium and Magnesium levels. Some of these kits will give you Calcium but Magnesium in freshwater IIRC is not easy to measure. I've not used any kits myself but if you search on the bottled water threads there is some good info in there.

Your local water authority might specify what is in your tap water if you are lucky (try their website)

If your water is very hard you can try boiling it first then filtering it.


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## El carajillo (Mar 16, 2013)

I think you come under Severn Trent W. A., you can obtain a rough guide from their website or telephone and ask for more detailed report. I think your water is fairly hard. Although the filter you mention does add too improve taste you may need to remove more of the hardness.

There is a thread on water and I believe test kits are mentioned.

Have a word with Xpenno:good: Water man


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## GlennV (Mar 29, 2013)

The API GH/KH test kits are good, with many suppliers on ebay. If your water is moderately hard then the BWT jug should do a good job with a new filter. The filter will lose it's ability to reduce hardness fairly rapidly, but you can keep track of that with the test kit.


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## aaroncornish (Nov 7, 2012)

We have super soft water, literally no KH buffering or alkalinity. I am about to try the Mg2+ cartridge to see if it improves the water.

Then I am going all in and trying Spencer's water voodoo - http://grindscience.com/2015/08/making-water-for-coffee-sodastream-method-best-recipe-so-far/


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## johnealey (May 19, 2014)

Evesham water fairly hard and will be close to what you have in Cheltenham. Bwt jug does a reasonable job for no more than 3 weeks for us (mg2+) but is a way away from the clarity you'll get from Waitrose or Waitrose mix etc etc ( see the brewed threads for more detail)

You could get a jug and filter for around 10-12£ on amazon a while back or if you have a brita jug then the bwt filter drop straight in , so could in theory try it out for less than a fiver.

Will be a huge improvement on straight or even brita jug water though, just not quite as good as bottled or spencers special water mentioned elsewhere.

Hope of help.

John


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## jonbutler88 (Dec 31, 2015)

Thanks everyone for the responses. I got a very detailed breakdown of my tap water from Severn Trent, and it's pretty clear it would be a pain to get it up to scratch. I just brewed my first Kalita with a Volvic / Waitrose mix and it was definitely the best tasting cup(s) I've had from it so far, so that's sealed the deal for staying on bottled.


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## abelated (Apr 14, 2020)

Big old dredge here but I've been trying to tame my Cambridge tap water as best as possible until I can obtain funds for one of the big systems. I have been using a BWT mg+ filter for my pour overs with varying results (obviously, as performance varies over the filter life) but have generally found it to be OK if I run it for about 5 refils and then cut it with tap water 80/20.

In general if I don't add back some tap I find it tends to be quite a sour brew. I've heard magnesium can do this so maybe it's psychosomatic.


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## Rob1 (Apr 9, 2015)

The sourness is likely from low alkalinity after filtration rather than the additional Magnesium. The tap water you add probably brings alkalinity up.

If you've got a water report from your supplier it might tell you bicarbonates in mg/l or alkalinity or bicarbonates as CaCO3 (which is alkalinity). It might not be listed though which is why people use GH:KH titration kits.

I've never heard of Magnesium causing sourness. My water contains nothing but sodium, magnesium and bicarbonates and if anything it is sweeter with magnesium than without, though it's likely just a matter of perception due to a change in mouthfeel.


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