How do water softeners work?

[Agentgonzo]

We've just had a water softener installed with our new kitchen (loving it).

The engineer/scientist in me is how wondering how they work. I've done lots of searches for it, and largely get publicly videos saying how great they are and the benefits, and even the more technical ones only go as far as saying there is a resin bed that performs ion exchange and needs regeneration.

Does anyone have a more detailed scientific explanation of what is going on. How/why are the Ca ions replaced by Na ions. How does the resin bed actually work. What happens with a regeneration cycle? How is the composition of the water changed by the resin bed?

Thank you in advance!

 

[LeeH]

We have one, probably the best 600 quid I’ve spent.

I understand the operation but not the chemistry side.

The resin bed takes out thinks like calcium, the salt (brine) washers it out of the resin into the foul water.

You need to treat the resin twice a year to get the best out of them. I use the kit below

https://www.bwt.com/en-gb/products/softener/bwt-aqa-clean-and-protect/

 

[Hazelwood Brewery]

We've just had a water softener installed with our new kitchen (loving it).

The engineer/scientist in me is how wondering how they work. I've done lots of searches for it, and largely get publicly videos saying how great they are and the benefits, and even the more technical ones only go as far as saying there is a resin bed that performs ion exchange and needs regeneration.

Does anyone have a more detailed scientific explanation of what is going on. How/why are the Ca ions replaced by Na ions. How does the resin bed actually work. What happens with a regeneration cycle? How is the composition of the water changed by the resin bed?

Thank you in advance!

I’m not sure I have all the facts but might get some way there…

The resin beads are produced to have a negative charge so attract positively charged ions. Sodium and calcium are both positively charged ions.

The resin beads are initially flushed with sodium from the brine produced from the salt blocks in the water softener.

During operation, hard water is passed over the resin beads and the calcium ions forming the water hardness displace the sodium ions because calcium is more positively charged.

After a while the resin beads become saturated with calcium ions and the resin beads can no longer remove calcium, this is where the regeneration cycle comes in.

The regeneration cycle is a repeat of the flush with sodium (brine). The brine is highly concentrated and displaces the calcium through it’s overwhelming concentration. Without the regeneration cycle the resin beads would continue to be saturated.

 

[Agentgonzo]

That's good - and makes a lot of sense. Thank you.

Hardness is a measure of bicarbonate (or is measured as a concentration of bicarbonate).

Does a softener reduce/remove bicarbonate?

 

[Hazelwood Brewery]

That's good - and makes a lot of sense. Thank you.

Hardness is a measure of bicarbonate (or is measured as a concentration of bicarbonate).

Does a softener reduce/remove bicarbonate?

You need to remember that hardness in this context is not about water chemistry, it’s how “hard” it is to lather up soap.

The softener will reduce calcium carbonate but increase sodium bicarbonate.

 

[Agentgonzo]

So why don't we get sodium bicarbonate buildup on taps etc the same way we get calcium carbamate build-up?

 

[Hazelwood Brewery]

So why don't we get sodium bicarbonate buildup on taps etc the same way we get calcium carbamate build-up?

You possibly do but sodium bicarbonate just wipes away easily.

 

[devexwarrior]

I live in Pembrokeshire with the softest water you can imagine. A ten year old kettle looks like new inside.

 

[Jason Rainwater]

Hazelwood Brewery gave an excellent description of how a water softener works. I have added a little more below...​

To confirm, the resin bed inside the softener is a strong cation resin which attracts positively charged ions including but not limited to calcium and magnesium. For every 2 molecules of calcium or magnesium removed one sodium ion is released into the water. As previously explained the resin bed has a finite capacity which is programmed into your water softener valve using your water hardness in ppm, when the capacity is reached a regeneration cycle occurs to clean the 'hardness' ions from the resin beads and prepare them to continue softening your water.

There are 3 stages involved in the regeneration cycle (What Is A Water Softener And How Do They Work? - Ultra Soft) :

1. Draw Of Water From The Brine Tank – This is where water heavily concentrated with salt is drawn from the ‘brine tank’ and flushed through the resin beads. This bombardment of sodium ions helps to dislodge the hardness ions from the resin beads in a process known as ‘reverse ion exchange’ which usually takes up to half an hour.
   
   
2. Resin Bed Rinse – Using the softeners normal feed water the resin bed is slowly rinsed in order to churn up all of the beads, dislodge any final hardness molecules and dilute and eventually eliminate the presence of that salty brine that was used to re-charge the resin beads. This tends to take around 30-45 minutes.
   
   
3. Brine Tank Re-Fill – The final stage of the regeneration process is the re-filling of the brine tank. This is where the brine tank refills with water that has the required volume of salt dissolved in it to ensure that the softener is ready and waiting for its next regeneration.

To be classed as a 'water softener' as opposed to a 'water conditioner' the calcium and magnesium ions need to be physically removed from the water, as opposed to having their chemical state altered to reduce scale formation which is what a water conditioner does.

Hazelwood Brewery is correct again in saying that sodium bicarbonate could still cause spotting on glassware in high concentrations, however it is easily cleaned away unlike spotting caused by permanent hardness in the water.

 

[Agentgonzo]

How does it do all of these different cycles? Mine seems to be entirely unpowered. The only things coming out of it are tubes for water and big blocks of salt in the front.

 

[Hazelwood Brewery]

How does it do all of these different cycles? Mine seems to be entirely unpowered. The only things coming out of it are tubes for water and big blocks of salt in the front.

It’s water powered. In the water flow is a paddle wheel on a shaft that powers a rotary valve. The rotary valve opens and closed ports that direct the flows.

 

[Agentgonzo]

Clever!

 

[Northern_Brewer]

For every 2 molecules of calcium or magnesium removed one sodium ion is released into the water.

Other way round shurely, Ca and Mg are 2+ ions, sodium is 1+ so you need two sodium ions to balance one Ca/Mg

So why don't we get sodium bicarbonate buildup on taps etc the same way we get calcium carbamate build-up?

1+ salts are generally a lot more soluble than salts of 2+ ions like calcium, so it's generally washed away in the water.

Carbamates are something rather different, they include a number of insecticides and the bonds formed in polyurethanes!

 

[Jason Rainwater]

Other way round shurely, Ca and Mg are 2+ ions, sodium is 1+ so you need two sodium ions to balance one Ca/Mg


1+ salts are generally a lot more soluble than salts of 2+ ions like calcium, so it's generally washed away in the water.

Carbamates are something rather different, they include a number of insecticides and the bonds formed in polyurethanes!

You are correct, I'd got that the wrong way round. Two sodium ions are displaced by the Ca or Mg ion in order to remain neutral.

 

[Agentgonzo]

1+ salts are generally a lot more soluble than salts of 2+ ions like calcium, so it's generally washed away in the water.

Oh, that makes a lot of sense. Thanks!

 

[ChrisT]

We've just had a water softener installed with our new kitchen (loving it).

We've been thinking of getting a water softener on and off for the last few years, for the whole house not just for brewing!

Appart from the initial costs what are the running costs like and how complicated to replenish consumables? I don't know anyone who's got modern equipment and the old ones I've been made aware of were bulky and not easy operate?

 

[Hazelwood Brewery]

Maybe don’t use softened water for brewing, the sodium content will be very high.

This is mine (the lump on the right with the blue panel not the small water filter) and it serves the whole house. It’s nearly 20 yrs old now. About once a month I drop 2 new salt blocks in. That’s it.

 

[ChrisT]

@Hazelwood Brewery That drawer is a very interesting way of improving internal storage!

If that's all the consumables then I think even SWMBO could cope, maybe... She'll still be afraid of breaking it though.

So NOT for brewing? I'll need a "raw" feed somewhere as well then.

 

[Hazelwood Brewery]

We don’t soften the water to the outside tap and my brewshed is tapped off that feed.

 

[Agentgonzo]

Mine is the same setup as Hazelwood's. Two blocks if salt in when they disappear. About every month apparently, though we haven't had to replace them. I think it's about £5 per block. So dead easy and cheap.

Our kitchen tap is unsoftened (this is normally recommended - as well as the garden tap). I brew from that.