Sand filter maintenance problem

[tripletango]

I got my pool out of balance and had an algae problem. Basically a heavy bather load was not properly taken into account. The FC was raised to 30 ppm with HTH, the CYA was around 70, Alkalinity was low due to rain corrected with sodium bicarbonate to 100 ppm. Calcium level is 260 ppm
Got a huge milky water problem that yielded a white back wash flow. I am guessing that this is the dead algae
The cloudiness would not filter quickly. Opened the filter a TR 140 Pentair and found a lot of hairy scum in the sand around the sides, clearer towards the middle. Filter in service for about 5 years, backwashed only.
I am removing the good sand and washing it and reusing, in addition using 200 lbs of new sand for final fill in top of filter.
Sand in Honduras where we are located is close to $20 per bag as it is all imported. (900 lbs needed for full refill)
When refilling with water before backwashing, will add filter cleaner and allow to sit for a day.
I have a 45 foot negative edge on this pool and no skimmer so don't have a way to add the filter cleaner during a back wash.
Question, Is it better to use pebbles beneath the laterals?
Any ideas on procedure would be appreciated.
Thanks Richard

 

[tripletango]

One other point. The filter was full of dirty water all the way through. The initial water color from the drain was brown. That is blown dust and above that grey. I believe that I was never backwashing this filter enough. Basically I wo=uld watch the outflow and as soon as it became clearer I rinsed and filtered. That maybe a minute or so. In future I will backwash for at least 3 to 5 minutes. Quite a bit of water at 160 gpm but i have plenty of water in my stream so costs only chemicals.
One other point salt is 15 bucks a bag here too and it rains a lot. The pool is now a chlorine based sanitation system using external sources depending on various levels CYA CA etc. Bleach is expensive here too so mostly Dichlor or hth type calcium Chloride.
Richard

 

[Bama Rambler]

I agree that you weren't backwashing long enough.
Since it rains a lot I think you can manage the CYA and CH levels by careful planning. Take a look at some of Richard320's posts to see a good example of water planning. He had high CYA and CH but has managed to bring it down using roof runoff and planning.

 

[duraleigh]

I have that same big filter and it runs troublefree. HOWEVER, in addition to some pretty good backwashes during the season, each spring I open it up and redistribute the sand and clean it out with a hose and sifter. I didn't do that the first four years and I had quite a mess so I learned my lesson.

Mine takes only about 30 minutes to clean it really thorough and about the same amount of time to open it up and button it back down....1 hour total.

 

[Puffin]

Dave and Richard, do you have top mount or side mount sand filters?

Dave could you describe the process you go through to clean your filter? Do you actually remove the sand and sift it?

 

[JasonLion]

There are instructions on cleaning a sand filter in this topic.

 

[Puffin]

Ah ok, since he mentioned a sifter I though it was a different technique.

 

[JasonLion]

A sifter can be handy if there is debris in the sand that doesn't float. Start with the water hose as described and by the time you are done with that you will have a good idea if you want/need a sifter.