Saturday, April 4, 2009

Don't Add Water

About 10 years ago, when we still had kids all over the place, we installed an 8m x 4m swimming pool in the garden.
I'm not totally convinced it was a good idea, but we have it now so we keep using it & enjoying it, in spite of the ecological reservations.

We initially filled it with 48 cubic meters of tap water (what else?).
During the first year or so, we had to add tap water occasionally to keep the level up to the recommended mark.
Every spring, following instructions, we drained one third of the water out & refilled with 16 m3 of new tap water.
This was expensive & embarrassing.

For the last 3 years, we have not added any tap water at all, which pleases me economically & ecologically.
A combination of several small ideas…

We keep the floating cover on the pool whenever it is not in use.
This reduces the evaporation of water & probably of active chemicals too.

When removing the floating cover, we roll it up slowly, so water on its dimpled underside has time to run back into the pool.
Then we stand one end of the rolled-up cover on a small block for a few minutes, so several more liters of water run back into the pool instead of getting lost elsewhere.

One of the skimmers has an overflow to prevent the pool over-filling in heavy rain, but whenever the pool does fill to that level, then as soon as it is used, the level falls several centimeters below the overflow lip.
This is because of surface waves – water keeps disappearing down the overflow so long as the tips of the waves are above the overflow.
So we have blocked the overflow with a removable rubber bung, knowing that we now have to keep an eye on the level after heavy rain.
The level does now get above the overflow, and can stay there for days or weeks, but so far has never got high enough to need any draining.
This means it takes a long time after heavy rain for the level to sink to the "add" mark – in fact it rarely does now.
When it does get that low, we have to keep an eye on it, to make sure the circulation stays OK until the next rain, but so far it always has.

But what about the 16 m3 refill every spring?
Well, we now do the draining in the autumn, then leave the concave winter cover on, which drains all rainfall through a central mesh into the pool.
By the time we want to use the pool in the spring, it is up to a useable level by rain & snow alone – at least it has been so far, though maybe not guaranteed every year.

But 16 m3?
No – now we only drain about half as much as was initially recommended & it seems OK so far.
Maybe because we found a more efficient treatment system.
After several years of juggling with fast & slow chlorine tablets, coagulants, anti-algae liquids etc etc, with frequent attacks of algae, cloudiness, green pool & so on, we tried Mareva Revaqua.
This is a pre-packaged 'sock' with doses of several elements (chlorine based) which you simply add to the skimmer once a week, with a measured dose of their anti-algae liquid.
In 4 or 5 years use, we have never had any off-colour water or other bother.
The snag is that it is more expensive than traditional chlorine tablets etc – if you renew it every week.
But after a long period of satisfactory use, we tried stretching it to every 10 days, which was OK, then every 2 weeks, then every 3 weeks and now even every 4 weeks except when the pool is around 30°C.
And it still works just fine, so it's not expensive at all.
And because we use so little chemicals, we think (hope) we can get away with changing less water every winter.

And that's how we get by with no added tap water.

Now we need to find a way to use less electricity for the circulation/filtration system…

Parting thot: "When you reach the top, keep climbing." – Zen proverb

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