hardness

Total hardness and calcium hardness in pool water.
Scale, calcium buildup, hard water and scaling problems.
guest

hardness

Postby guest » Sat 05 Jan, 2008 16:26

is it possible to reduce hardness from 200 to 0, and is it true that having 0 hardness is bad?


chem geek
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Postby chem geek » Sat 05 Jan, 2008 19:07

Total Hardness is not the important parameter. Calcium Hardness is what matters and you don't want this to go to zero or to be too low in plaster pools. Otherwise the water will tend to dissolve the plaster. One wants the water saturated with calcium carbonate in order to not dissolve pool plaster (or grout in tile exposed to the water).

It is less clear whether low Calcium Hardness is a problem for fiberglass or vinyl pools or in spas, but if the hardness is too low then foaming can occur so usually even in a spa one wants around 100-150 ppm Calcium Hardness (CH).

The only ways to lower hardness are through dilution with water that is lower in hardness or through addition of a metal sequestrant that is optimized to lower calcium or total hardness -- these are sometimes called scale inhibitors or hardness reducers. They only temporarily hold the calcium (and magnesium) and will break down over time so additional product needs to be added periodically.

Richard
rwinkels

water hardness

Postby rwinkels » Sun 24 Feb, 2008 12:14

Our Water hardness is at about 830. The local pool store said we have to drain some water and then add it back.

He said my adding water back after it evaporates doesnt help as I am just adding hard water back in. This doesnt make sense to me as either way I have to use the hose to add water back in.

Is there a better way to lower the hardness in the water rather than draining it and adding it back?
chem geek
Pool Industry Leader
Pool Industry Leader
Posts: 2382
Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Postby chem geek » Sun 24 Feb, 2008 14:21

If your fill water is high in hardness, then drain/refill doesn't do much good. It's only if your fill water is lower in hardness that a partial drain/refill will lower the hardness. If your fill water is high in Calcium Hardness, then using a water filter with a large capacity (i.e. whole house filter) is one option. Another is to use a calcium sequestrant.

It is possible for the hardness level in the pool to increase over time via evaporation and refill with water that has moderate or high hardness. Evaporation only removes water while refill adds everything that is in the fill water.

Richard
rwinkels

Postby rwinkels » Sun 24 Feb, 2008 15:01

I guess I would have to test the fill water then.

what is cheaper? adding a calcium sequestrant or draining and refilling?

we dont see any scale or anything, the person at the pool store said we need to get the hardness lower so we can get the chemical balance right.

thanks again!
chem geek
Pool Industry Leader
Pool Industry Leader
Posts: 2382
Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Postby chem geek » Mon 25 Feb, 2008 02:50

I don't know which would be cheaper -- it depends on the cost of your water relative to the amount of sequestrant you need.

First of all, you need to really test the Calcium Hardness level, not the Total Hardness. Get yourself a good test kit, the Taylor K-2006 (not K-2005) which you can get at a good price here or you can get the TF100 kit here which has 36% more volume of reagents so is equivalently priced to the Taylor kit (and it uses Taylor reagents).

Unless your Total Alkalinity and pH are also high, you may not notice scaling even with a higher Calcium Hardness. Get a good test kit and then post a full set of numbers and we can see where you are at.

Richard

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