Using an underground water supply

[mikethaisun]

Good Morning from Thailand.
I have received really good advice on how to test and balance the pool water that comes from the town main water supply. I have a problem with high CYA levels and have been advised the remedy is to partially empty the pool and refill. That is not a problem, but water in this part of Thailand is expensive, the more you use the higher the unit rate becomes.

We have an underground bore from which we pump water to irrigate the garden, this is plentiful in supply and is free except for the electricity the pump uses. There is a small amount of salt and sediment in it, the sediment I suppose can be taken out by the filter but I am uncertain of the salt content and do not know how to test for it.

I have tested for the usual and the results are as follows: -
FC 0
pH 7.2
TA 360
CH 280
CYA 0

Is this supply worth trying and if so what do I need to do about the TA and CYA.
Regards
Mike

 

[JasonLion]

Some wells have high iron content, which can cause problems. Do you have any idea if iron is common in well water around there? If there is any iron in the water, it can mean either unsightly stains or constant use of a sequestrant.

Dealing with the TA will require quite a bit of acid and aeration, which can be a fair amount of work. Depending on what acid costs relative to water it could be worth it.

The CH level could cause problems long term if you get all of your water from the well. On the other hand, you probably get enough rain over the course of a year to be able to dilute it down over time, and it shouldn't cause any short term problems as long as you can get the TA down reasonably quickly.

 

[mikethaisun]

Hello Jason
Thank you for your reply. We use the well water for our irrigation system for the garden, it is pumped and stored in an open tiled reservoir for a fountain similar to the swimming pool and then drawn off when and where it is needed.
Would the presence of iron leave a black stain on the tiles? We sometimes get this where the feeder pipe to the reservoir is situated but not all the time.
When the rainy season is here I tend to keep the pool covered to keep out all the debris that falls in during the high winds, we don't just get rain we get a tempest!!
What effect would mixing well water and mains say at 50/50 have? I note your comment about CH but looking at the tables for recommended levels for a plaster pool, 280 seems to be OK or am I reading this section wrong?
I managed to buy 30kgs of Hydrochloric acid for about 60$ US and depending on how much I would need to use maybe the cheapest option.
Any further advice?
Thanks
Mike

 

[JasonLion]

Iron stains can be anywhere from a very dark brown to a light yellow. The stain you are seeing is sure to be a metal, perhaps iron, perhaps manganese, perhaps something else. Iron, and manganese, can be filtered out with a greensand filter, at least that is what it is called here.

When water evaporates it leaves all of the CH behind. If you then top off the pool with water that has lots of CH in it, the CH level goes up. In arid climates, with lots of evaporation, the CH level goes up quickly and eventually you need to replace all of the water. You should be able to avoid this by using some mains water and some well water but you will need to keep track of what the CH level is doing.