<p>Is it, by any chance, demineralised/distilled water, with no minerals added back in?</p>

<p>Aside from temperature (which you should check - it's OK if it's cooler, but too cool is no good, and knowing the temperature will help you modify other parameters), it's important to have high quality, odour-free water that is free from impurities and that has the correct mineral content. The SCAA actually specifies water standards (see <a href="https://www.scaa.org/?page=resources&amp;d=water-standards" rel="nofollow">here</a>). In many developed parts of the world, tap water is fine. However, demineralised water is NOT fine. It will underextract.</p>

<p>One solution*: Buy bottled mineral water (like Evian or a cheaper alternative), which usually has too HIGH a mineral content, and blend it with the filtered water from the dispenser. This may seem hard core, but it'd be good as an experiment to see if it cures your woes.</p>

<ul>
<li>Joke only intended after the fact</li>
</ul>

CC BY-SA 3.0
2016-02-17T10:34:22.880Z
If the water is demineralised, would adding a small amount of salt to the coffee before brewing achieve a similar effect?
fredley
CC BY-SA 3.0
2016-02-18T00:15:42.197Z
It seems there is no dispenser, but only a hot-water tap. The solution may no apply. I have such a setting in my offices too, although I don't use it for brewing at all (water is treated as you mention).
Eric Platon
CC BY-SA 3.0
2016-02-18T10:41:51.663Z
Is there an optimal mineral content for coffee extraction?  The water in my area is very hard, but is that actually a good thing when making coffee?
Will Vousden
CC BY-SA 3.0
2016-02-18T14:46:38.637Z
@fredley no, because sodium is only required in a small amount. Calcium and magnesium are also important. Look at the specs I linked as a guide.
Hoosh
CC BY-SA 3.0
2016-02-18T14:47:35.523Z
@WillVousden it's not a good thing for it to be very hard. There's an optimal hardness level. You can either get your water tested, or look at the local council webpages for recent tests in your area or at the reservoir.
Hoosh
CC BY-SA 3.0
2016-02-18T19:07:13.023Z
I have noticed on the water bottle i use daily and around the edge there is a small limescale deposit - so there is certainly something in the cold water at least.
NBenatar
CC BY-SA 3.0
2016-02-17T05:58:36.870Z
2016-02-17T05:58:36.870Z
Hoosh
<p>I would highly suggest checking the system which generates the hot water.  Regardless of if it is a storage type or on demand type system, it may require cleaning.  Storing water at temperature has a tendency to cause the contained minerals to accumulate in the container.  If you can take it apart and it is old (more than two years) you may find it has a wealth of accumulated minerals that are imparting "flavor" to your coffee.</p>

<p>If the system is not readily available for inspection, you may considered letting some water from it stand/cool and checking to see if the water has some of the flavor you are describing.</p>

CC BY-SA 3.0
2016-02-17T18:24:47.440Z
Its not really feasible to check the system.  The team who look after that sort of thing are usually quite good at maintenance - also the system is pretty new - less than a year old - we used to have an old school water boiler and separate water cooler.
NBenatar
CC BY-SA 3.0
2016-02-17T18:25:07.353Z
I will however try drinking the hot water (after its cooled) too see.
NBenatar
CC BY-SA 3.0
2016-02-18T19:06:16.213Z
It tastes bad.  Kind of chemically.  I checked under the sink and there is a Cylinder ("Ultra 2000 Water Treatment" from EverPure attached to the heating/cooling/filter unit).
NBenatar
CC BY-SA 3.0
2016-02-18T19:31:05.033Z
Hopefully that can be swapped for something that won't affect the taste for you.  Good luck!
Suspended User
CC BY-SA 3.0
2016-02-18T21:25:16.487Z
Unlikley.  Its a big site (2k employees, with probably 20+ breakout areas, each with this system) - I doubt they would change the process because one guy said he didnt like the water.  Especially as there is a cafe downstairs that serves pretty good coffee (its cheap, but 2 coffees a day still adds up)
NBenatar
CC BY-SA 3.0
2016-02-18T22:30:39.487Z
If the cold water is good, you may consider the purchase of a small electric water kettle to leave at work (if that is allowed).
Suspended User
CC BY-SA 3.0
2016-02-17T17:56:31.573Z
2016-02-17T17:56:31.573Z
Suspended User
<p><strong>I think you are attempting to brew with water that is way too cold.</strong> To me, this is the elephant in the room in your question.</p>

<p>Though it's only an anecdote (until you measure your water temperature!) I myself measured the "very hot" water taps from a filter machine and from a hot water dispenser in my office: one was 75°C and one was 85°C. The latter is actually the hot water dispenser from a coffee-brewing machine. Both of these are way below what I consider to be adequate brewing temperature (~95°C). I did as fair of a measurement as I could: reasonably calibrated instant-read thermometer, pouring water directly from the tap directly over the thermometer into a pre-heated mug.</p>

<p>See <a href="https://coffee.stackexchange.com/questions/2019/what-water-temperature-and-pour-speed-are-best-for-pour-over-method">this question about pour-over temperatures</a> and links from (full disclosure) my answer there.</p>

<p>It's also striking how quickly water cools: merely traveling through the air when pouring from a vessel can make the water drop a few degrees C. I think you will probably need a separate heating kettle, and I don't think you should ever expect to have to cool off water before brewing.</p>

<p>Or, like I said before in my original comment: measure the temperature and prove me wrong!</p>

CC BY-SA 3.0
2016-02-18T19:05:12.393Z
According to http://nordiccoffeeculture.com/what-is-the-best-way-to-brew-aeropress-coffee/ the ideal temp for Aeropress is around 75-85°C
NBenatar
CC BY-SA 3.0
2016-02-18T03:41:23.970Z
2016-02-18T03:41:23.970Z
2017-04-13T12:51:53.733Z
hoc_age
<p>Your hot water is not the problem - you just need to grind coarser! Especially if you're using a darker roast, which is more soluble and will extract faster. Cooling your water would of course help slow down extraction - but I think the grind is an easier variable to control. </p>

CC BY-SA 3.0
2016-02-25T06:57:32.620Z
This week I've gone for standard grind "suitable for all makers", it's not made much difference - it's a lighter roast than I normally go for too.  Tastes quite metallic
NBenatar
CC BY-SA 3.0
2016-02-25T07:09:06.837Z
Ah, if it's still metallic it sounds like it's unrelated to extraction then. Maybe you could try another water source if that's possible?
Induction
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2016-02-25T07:09:39.027Z
Sorry, just read the other comment talking about the water quality... Sounds like that may be your issue :)
Induction
CC BY-SA 3.0
2016-02-25T07:13:00.123Z
I'm afraid you're right and all sources of hot water go through the same system, unless I go to the cafe and get a cup of hot water
NBenatar
CC BY-SA 3.0
2016-02-25T06:43:49.497Z
2016-02-25T06:43:49.497Z
Induction
<p>In my office they have a tap with (boiling) hot and cold filtered water system - its designed for hot drinks, and is fine for black tea.  I assume it dispenses at around 100 degrees, though I have not measured it.  The cold tap gives chilled water - I'd assume 5-10 degrees.</p>

<p>I brew my coffee using an aeropress, with about 2 spoons worth of coffee and the standard paper filter. Filled up to a mark between the 2 and 3 marking on the aeropress.</p>

<p>What comes out has a slight metallic, bitter taste.  I do not get this at home where I use a standard kettle (either leave it to boil and cool for a few minutes, or use my new kettle that can specify the temp - I generally use 85-90 degrees)</p>

<p>I have tried to eliminate the problem thus:</p>

<ul>
<li>Different beans (2 different bags of fresh preground ground coffee, with both "standard for cafetiere grind" and espresso grinds).  Grinding at work is not an option and doing at home is too annoying.</li>
<li>Different storage (I thought the metal tin I was storing in was imparting bad flavour) - I have now got a glass kilner jar which is air tight and stored in a dark drawer</li>
<li>Washing the paper filter before use (I dont do this at home normally)</li>
<li>Using the inverted method (with the same, or slightly less grounds)</li>
<li>Using another breakout area (with the same system) in case the normal one is broken/dirty/etc</li>
</ul>

<p>None of this makes a difference so I assume it is down likely down to the temperature of the water being too hot.  </p>

<p>What is the best (quickest and least fussy) way of improving my brew?</p>

<p>I have considered (but not yet attempted):</p>

<ol>
<li>Adding a small amount of cold water before adding the hot (approx 1/4 cold to 3/4 hot) then brewing as usual.</li>
<li>Add the hot then add a splash of cold.</li>
<li>Mixing in another cup and adding that - this is undesirable as I already have to carry the coffee jar, aeropress and cup to the kitchen and back.</li>
</ol>

<p>What is the best means to get a better brew?</p>

CC BY-SA 3.0
2016-02-16T22:40:03.810Z
Step 1: measure the hot water temperature. My guess: 75°C... way too cold. Prove me wrong! :)
hoc_age
CC BY-SA 3.0
2016-02-17T07:20:06.860Z
Could it just be the local water and what you are used to? I find when I make tea at my parents house, it's almost undrinkable to me now as I find the water to metallic. I don't notice it as much when I'm drinking the water straight, but it's amplified when I make a cup of tea.
Consume Coffee
CC BY-SA 3.0
2016-02-17T07:21:43.657Z
It could be I guess.  There is also a water treatment thing attached the system I noticed today
NBenatar
<aeropress><brewing-process>
Brewing Coffee with instant hot water tap
NBenatar
# Brewing Coffee with instant hot water tap

(Asked by: username_0 on 2016-02-16)

In my office they have a tap with (boiling) hot and cold filtered water system - its designed for hot drinks, and is fine for black tea. I assume it dispenses at around 100 degrees, though I have not measured it. The cold tap gives chilled water - I'd assume 5-10 degrees.

I brew my coffee using an aeropress, with about 2 spoons worth of coffee and the standard paper filter. Filled up to a mark between the 2 and 3 marking on the aeropress.

What comes out has a slight metallic, bitter taste. I do not get this at home where I use a standard kettle (either leave it to boil and cool for a few minutes, or use my new kettle that can specify the temp - I generally use 85-90 degrees)

I have tried to eliminate the problem thus:

* Different beans (2 different bags of fresh preground ground coffee, with both "standard for cafetiere grind" and espresso grinds). Grinding at work is not an option and doing at home is too annoying.
* Different storage (I thought the metal tin I was storing in was imparting bad flavour) - I have now got a glass kilner jar which is air tight and stored in a dark drawer
* Washing the paper filter before use (I dont do this at home normally)
* Using the inverted method (with the same, or slightly less grounds)
* Using another breakout area (with the same system) in case the normal one is broken/dirty/etc

None of this makes a difference so I assume it is down likely down to the temperature of the water being too hot.

What is the best (quickest and least fussy) way of improving my brew?

I have considered (but not yet attempted):

1. Adding a small amount of cold water before adding the hot (approx 1/4 cold to 3/4 hot) then brewing as usual.
2. Add the hot then add a splash of cold.
3. Mixing in another cup and adding that - this is undesirable as I already have to carry the coffee jar, aeropress and cup to the kitchen and back.

What is the best means to get a better brew?

**Tags:** aeropress, brewing-process

> **Comments:**
> **username_1**: Step 1: measure the hot water temperature. My guess: 75°C... way too cold. Prove me wrong! :)  
> **username_2**: Could it just be the local water and what you are used to? I find when I make tea at my parents house, it's almost undrinkable to me now as I find the water to metallic. I don't notice it as much when I'm drinking the water straight, but it's amplified when I make a cup of tea.  
> **username_0**: It could be I guess.  There is also a water treatment thing attached the system I noticed today  

---

## 4 answers

### Answer by username_3 on 2016-02-17. Score: 2

Is it, by any chance, demineralised/distilled water, with no minerals added back in?

Aside from temperature (which you should check - it's OK if it's cooler, but too cool is no good, and knowing the temperature will help you modify other parameters), it's important to have high quality, odour-free water that is free from impurities and that has the correct mineral content. The SCAA actually specifies water standards (see [here](https://www.scaa.org/?page=resources&d=water-standards)). In many developed parts of the world, tap water is fine. However, demineralised water is NOT fine. It will underextract.

One solution\*: Buy bottled mineral water (like Evian or a cheaper alternative), which usually has too HIGH a mineral content, and blend it with the filtered water from the dispenser. This may seem hard core, but it'd be good as an experiment to see if it cures your woes.

* Joke only intended after the fact

> **Comments:**
> **username_4**: If the water is demineralised, would adding a small amount of salt to the coffee before brewing achieve a similar effect?  
> **username_5**: It seems there is no dispenser, but only a hot-water tap. The solution may no apply. I have such a setting in my offices too, although I don't use it for brewing at all (water is treated as you mention).  
> **username_6**: Is there an optimal mineral content for coffee extraction?  The water in my area is very hard, but is that actually a good thing when making coffee?  
> **username_3**: @username_4 no, because sodium is only required in a small amount. Calcium and magnesium are also important. Look at the specs I linked as a guide.  
> **username_3**: @WillVousden it's not a good thing for it to be very hard. There's an optimal hardness level. You can either get your water tested, or look at the local council webpages for recent tests in your area or at the reservoir.  
> **username_0**: I have noticed on the water bottle i use daily and around the edge there is a small limescale deposit - so there is certainly something in the cold water at least.  

---

### Answer by username_7 on 2016-02-17. Score: 1

I would highly suggest checking the system which generates the hot water. Regardless of if it is a storage type or on demand type system, it may require cleaning. Storing water at temperature has a tendency to cause the contained minerals to accumulate in the container. If you can take it apart and it is old (more than two years) you may find it has a wealth of accumulated minerals that are imparting "flavor" to your coffee.

If the system is not readily available for inspection, you may considered letting some water from it stand/cool and checking to see if the water has some of the flavor you are describing.

> **Comments:**
> **username_0**: Its not really feasible to check the system.  The team who look after that sort of thing are usually quite good at maintenance - also the system is pretty new - less than a year old - we used to have an old school water boiler and separate water cooler.  
> **username_0**: I will however try drinking the hot water (after its cooled) too see.  
> **username_0**: It tastes bad.  Kind of chemically.  I checked under the sink and there is a Cylinder ("Ultra 2000 Water Treatment" from EverPure attached to the heating/cooling/filter unit).  
> **username_7**: Hopefully that can be swapped for something that won't affect the taste for you.  Good luck!  
> **username_0**: Unlikley.  Its a big site (2k employees, with probably 20+ breakout areas, each with this system) - I doubt they would change the process because one guy said he didnt like the water.  Especially as there is a cafe downstairs that serves pretty good coffee (its cheap, but 2 coffees a day still adds up)  
> **username_7**: If the cold water is good, you may consider the purchase of a small electric water kettle to leave at work (if that is allowed).  

---

### Answer by username_1 on 2016-02-18. Score: 1

**I think you are attempting to brew with water that is way too cold.** To me, this is the elephant in the room in your question.

Though it's only an anecdote (until you measure your water temperature!) I myself measured the "very hot" water taps from a filter machine and from a hot water dispenser in my office: one was 75°C and one was 85°C. The latter is actually the hot water dispenser from a coffee-brewing machine. Both of these are way below what I consider to be adequate brewing temperature (~95°C). I did as fair of a measurement as I could: reasonably calibrated instant-read thermometer, pouring water directly from the tap directly over the thermometer into a pre-heated mug.

See [this question about pour-over temperatures](https://coffee.stackexchange.com/questions/2019/what-water-temperature-and-pour-speed-are-best-for-pour-over-method) and links from (full disclosure) my answer there.

It's also striking how quickly water cools: merely traveling through the air when pouring from a vessel can make the water drop a few degrees C. I think you will probably need a separate heating kettle, and I don't think you should ever expect to have to cool off water before brewing.

Or, like I said before in my original comment: measure the temperature and prove me wrong!

> **Comments:**
> **username_0**: According to http://nordiccoffeeculture.com/what-is-the-best-way-to-brew-aeropress-coffee/ the ideal temp for Aeropress is around 75-85°C  

---

### Answer by username_8 on 2016-02-25. Score: 0

Your hot water is not the problem - you just need to grind coarser! Especially if you're using a darker roast, which is more soluble and will extract faster. Cooling your water would of course help slow down extraction - but I think the grind is an easier variable to control.

> **Comments:**
> **username_0**: This week I've gone for standard grind "suitable for all makers", it's not made much difference - it's a lighter roast than I normally go for too.  Tastes quite metallic  
> **username_8**: Ah, if it's still metallic it sounds like it's unrelated to extraction then. Maybe you could try another water source if that's possible?  
> **username_8**: Sorry, just read the other comment talking about the water quality... Sounds like that may be your issue :)  
> **username_0**: I'm afraid you're right and all sources of hot water go through the same system, unless I go to the cafe and get a cup of hot water  

---

