Pool Water Stratification

Know exactly the problem you refer to, and strongly agree with you regarding draining that pool for so many reasons, however one mitigating technique if you DO decide to drain. You can set sprinklers in the pool to keep the plaster wet during drain and refill. But trying to get things like pH to stabilize with those hardness levels is a nightmare.

Stratification I cannot address - intriguing idea though.

I'd be tempted to use down-time during the week and mechanical separation with a membrane (tarp) and pump from the bottom, fill from the top until tarp hits bottom. Probably problems I am not anticipating with this. Like cold water weighing more and ripping my tarp restraints apart.

One thing to be wary of - right now your city water (while better than what is in your pool) is also at the peak for hardness because of open transport during summer months.

Other options - I hadn't investigated this (it didn't exist when I needed it) is pool water service companies. Giant truck pulls near your yard, drains yours FAST with giant pumps, then refills with wholesale priced water from the hydrant.

Better, some of these firms actually run the city stuff through a water softener process first.

Can't help with costs. But the process is fast enough to prevent plaster damage.

Good luck!

ED,

Some good ideas that I had not considered. If I were going to pump mechanically, I would definitely consider the membrane approach. I want to siphon the water out to reduce the accumulation of water in the yard (Kids and dogs!). And we aren't supposed to pump it into the street/sewer.

I'll ponder for awhile.

Thanks.

LL

Not questioning you - but not into the sewer?

The cities are steadily losing their minds.

If lime and carbon dioxide are cheap in your area, you can use the lime to raise the pH of your pool water to > 11.0. This will precipitate out the hardness. Bubbling CO₂ through the water will then precipitate out the lime as calcium carbonate. The precipitated solids can then be filtered out and your pool water reused.

That's not something they tell pool owners!

heh heh - backyard science - wait'll you get to lean over the fence and tell the neighbor you are precipitating the hardness out of your water!

I recall a project where oceanographers were building underwater structures with electro-deposition. They put a metal mesh structure underwater, applied DC, and plated mineral deposits onto the mesh. I wasn't fast process, but does look inexpensive to try.

I read about that too. VERY cool idea. They couldn't call it cultured marble though, that's already taken. Cultured limestone would probably be more accurate anyway.

So, If I get a piece of hardware cloth, hook it to a battery charger and throw it in the pool, I can plate the minerals out?

I might try that. Looks fun and cheap to try.

Thanks,

LL

Yes, apparently so.

The structure in the article looked like rock - calcium and/or silica probably. I think the voltage was quite low, maybe one or two volts.

Please report on your results, I have always thought it was a great idea.

Good luck

Dave

I have obtained suitable materials for the plate out test and will begin this weekend.

Well? How did it go?

<...will the denser, mineral laden, water settle to the bottom to be carried away, or will the density of the water remain constant throughout the depth of the pool...>

It depends upon the level of agitation caused by swimming in it, agitation caused by pumped recirculation, and any thermal agitation effects. Generally, there should be very little difference in dissolved solids between top and bottom.

Dissolved solids generally stratify very little. It is another story for suspended solids!

I like the idea of a membrane as well. One thought would be to use a dark tarp bigger than the pool. Add fresh water through a solar heated hose to the center on top of the tarp. I think the dark top would help heat the water on top (if sunny) and not the water on the bottom. The higher solids and cooler water under the tarp should remain denser than the water on top and go to the bottom to drain.

I don't know what to do if night temperatures cool the top more than the bottom. Is the water supply colder than whats is in the pool? Can it be changed in in 12 hours?