Filter size

[lilpam14]

OK so how can I figure out what size sand filter is needed. The pool is marcite, aprox. 20,000 gal, no heater. I am guessing it is a 300 lb filter but only guessing by the size of the old one and comparing it to others I have seen. I would look at the label on the old one but cannot get to it to see it. (faces the neighbors fence and not enough room to get in between)
Trying to get a friend to replace his filter or at least clean it. The pool has been there for about 17 yrs, he has owned it for 14 of those. Never has he cleaned the sand or ever replaced it. Have had ongoing algae problems with doing all the right things using the BBB method. My guess is filter needs to be cleaned and replace the sand. He is willing to replace everything, rather than just the sand.

 

[jblizzle]

Based on the chart in "have you lost your head", we would recommend 3.7sqft sand filter, that is a 26" diameter, filter for that size pool.

Although the filter has nothing to do with algae growing. That only comes from a lack of chlorine. If the filter sand was climbed and channeled, that water would stay cloudy though since it would not filter very well.

Posted from my Droid with Tapatalk ... sorry if my response is short

 

[lilpam14]

Not short response at all Jason. Concise, to the point and informative, as always. THANKS. Chlorine levels were consistently high while it was happening, so I thought myabe the filter may be the culprit??? Still don't you think the 14 years is too long to go w/o cleaning or changing sand? I know there are those on here that say they have never cleaned their sand or changed it but...others say clean it once a year and change it every 2-3. Any other thoughts?

 

[y_not]

The general consensus is, don't change it!!!
Sand never wears out, never really wears down. If it did, we wouldn't be able to use it for our pools. Cause it'd be too worn down already.
If you really want to pour through a very long thread on this, discussing the nerdy intricacies of it all. I can link you up, otherwise, that's the gist.

The most that can happen is that it gets so incredibly caked with goo (oils) and gunge (caked organics) and yuck (unknowns) that you can't get it clean by any traditional means. But there are ways if it is that far gone. It should never get that bad though, so long as one maintains proper water chemistry and cleans it whenever the filter PSI hits 20-25% above clean starting pressure.

Do clean & resettle the sand bed each season though. Whether you do it at the start of the season or at the close, doesn't matter. So long as it happens each season.

The link for this is in my sig.
If it has truly been 15 years or so, it may take a bit of extra work the 1st time. But it's a pretty simple and painless process.

PS. If you have algae in that pool, you need to do go through the full shock procedure as outlined in Pool School. Read all the algae posts, included "Turning Your Green Swamp Back into a Sparking Oasis".

 

[duraleigh]

Only posting to agree with what y_not has already posted. Clean your sand annually and there is no need to change it.

Most (if not all) sand filters have a GPM rating in the specs. It should be about 20% or so more than the GPM of the pump curve. In other words, think of the pump and filter as a set and match them up.

A 3/4 or 1HP pump (around 70-80GPM) would usually fit nicely with a 20k pool so a filter matching that pump should have about a 100 gpm rating.

 

[y_not]

Only posting to agree with what y_not has already posted. Clean your sand annually and there is no need to change it.
....

Thank you so much duraleigh.
Great info on the filter sizing I might add. Good stuff there.