Why Swimming Pools Turn Green
It is not uncommon in the Oklahoma City area, or anywhere else, for that
matter, for a swimming pool to turn green because of algae. When dealing
with a chlorinated pool, this happens for one reason - there is not enough
available chlorine in the pool. (see
Pool Chemistry ) There may be a number of reasons why the chlorine level is low, but the
simple answer is that not enough chlorine has been added to satisfy the raw
demand of the water. Raw demand is amount of chlorine required to keep the
water clear, sanitized, and able to maintain a residual. I often hear
people say that they have put "tons" of chlorine in the pool, and that the pool
is still turning green. The reason for this is that the raw demand has not
been met. Satisfying the raw chlorine demand of the water is one of the
most critical steps in
opening a
pool in the spring, and unfortunately, is not always done even by
people who are hired to open the pool. It is absolutely critical in
chlorinated pools to put enough chlorine in the pool to kill everything in the
water, and establish a residual - even if that means you can't get in the pool
for a few days. Failure to do so can cost a lot of money and aggravation.
If algae is treated with chlorine, it must all be killed in one shot. If
any algae survives, it will become more resistant to chlorine, much like
infections that are not killed with antibiotics. If 4 pounds of chlorine
are needed to kill all of the algae, and you put in 3 pounds, you not only
wasted the three pounds, you made the algae more resistant to chlorine, and you
will fight it the whole season! You need to kill it all within 48 hours,
or you have lost. Other reasons why pools are unable to maintain a
chlorine residual include heavy usage, high temperatures, rain, and lots of sun
in pools which are not stabilized. No matter why the pool turned green,
the solution is the same. Nip it in the bud!
Clearing Up a Green Pool
The most cost effective way to clear up a green pool is to first remove
the worst of the fine debris before applying chemicals. You should
not, at this point, be reaching for a dip net, except to use on the top of
the water! You don't want to disturb what is on the bottom or walls of
the pool any more than you have to. Vacuum to waste, then
clear up the water. You will have removed the worst of the debris,
and, since you can see them, the leaves are much easier to get out.
There may be some exceptions, but, generally, this is what we do:
Vacuuming To Waste
If You have a sand filter or diatomaceous earth
filter, you most likely have a six position rotary control valve. You want
to use the
Waste (a.k.a.
Pump to Waste) position, not
Backwash ( if you need to know more about how to operate your filter,
visit
[ How Pools Work ]
).
When Vacuuming to waste, obviously, you will be loosing a lot of water from
the pool, so you will want to start with the pool as full as you can get it,
and don't waste any time. You may even have to stop for a while to let
the pool refill. Vacuuming the pool on waste is exactly the same as
normal vacuuming, except that instead of the water going back to the pool,
it is going down the drain. The reason for doing this is because algae
is so fine that much of it will pass through a sand filter, and return to
the pool, and be suspended in the water. A diatomaceous earth filter
would clog up very quickly, if the debris is heavy.
By the way, waste water from the pool is supposed to go
into the sanitary sewer, not into the street, so that it is treated before
being released into the fresh water supply. Most communities in the
Oklahoma City area have ordinances against draining pool water into the
street, but, actually, if no algaecides or sanitizers, the water can
be used to water lawns, and other non-food plants.
