Sand Filter Sizing Recommendations

[MBoz]

This is our second summer in our 1976 home. Our pool filter might be as old as the pool and home itself. Last summer, we called the pool guy the previous owners had used for years. He commented on the fact that the filter was OLD, and we'd be needing a new one sooner than later. He's a nice, humble, trustworthy man, so we didn't feel as if he was "out to get us". After last year's disastrous Summer, we are in agreement that no amount of chemicals can make this pool usable without a new filter. Noteworthy, is our pump is in good shape.

I just called the pool guy to inquire about a new filter installation. He does not believe our pool is 44,000, as we were told. The measurements of our rectangular pool are 40x20, with the deep end supposedly 10' and the shallow perhaps around 4 or 4.5'.

The pool guy is recommending a 300 pound, 26' sand filter for us.

I'm curious to know the experts' thoughts here. Thanks, in advance.

 

[zea3]

Hi, welcome to TFP! Before we get to the size of filter you need, how big is the current filter and is it having any problems? Most water clarity problems are chemical problems and not filtration problems.

 

[Texas Splash]

Welcome to TFP! You have quite the pond there. 44K at 10'. Nice! Okay, before you rush-out to get a new filter, which may very-well be needed, let's get a little more info about your situation. Such as.....
- Please update your signature with all of your pool and equipment info. Anything that may apply. See mine as an example. Make sure to include your test kit.
- Speaking of which .... we hope it's a TF-100 or Taylor K-2006C. If not, please see Test Kits Compared.
- Why do you think you need a new filter? Is the water cloudy or green? Something else?
- Can you post a full set of water results?
- Can you post a pic of yoru filter?
- Have you ever opened it up and done a deep clean?

I suspect you would need at least a 300 lb filter, but others will confirm.

 

[MBoz]

Hello again...

I've included a signature and pics of the filter and pump.
I have yet to order test kit, but I will take your recommendations and order one, especially after one trip to the pool store.

Water results are as follows:
pH: 8.7
Free Chlorine: 0.2
Saturation Index: High
Alkalinity: 98
Total Chlorine: 0.4
Total Hardiness: 105
CYA: 5
TDS: 415

I have some pool school articles, and I know that you all do not recommend taking note of all these results, only certain ones.
Yes, we opened it up at the end of last year, and cleaned it out with a water hose for a great amount a time, letting all the stuff float to the top and wash off. Plus, we added a set of chemicals to chemically clean the sand.
There is really not a reasonable way to change the sound out with this antique model and its placement in the pool house.
One skimmer way, way slower than the other one. And one jet doesn't appear to be shooting out as strongly.

 

[MBoz]

Ahhh..... I forgot to say that last summer we did all we could to make a go of it to no avail! Cloudy water and then a burst of green algae. It was a constant cycle of misery.
Thank you all so much! I'm already a fan because now - I have hope!

 

[zea3]

Water results are as follows:
pH: 8.7
Free Chlorine: 0.2
Saturation Index: High
Alkalinity: 98
Total Chlorine: 0.4
Total Hardiness: 105
CYA: 5
TDS: 415

First thing I would recommend is to get the pH down in the low 7's with some muriatic acid. It may take several doses to drop it that far. For now the saturation index and TDS can be ignored. Those numbers will change when the pool is balanced. Your FC and Calcium both need to come up. I don't really trust that CYA number at all, so I hesitate to ask you to raise it at this time. Until we can confirm the CYA level you should add enough liquid chlorine to reach 3ppm. Walmart and some big box hardware stores sell the HtH 6 way pool test kit. It has enough reagent to run a couple of accurate tests and can get you by until your new test kit arrives.

A 300 lb filter is only slightly larger than what you have now. Since the current filter is in a pool house, where does the waste water go when you backwash? The area around the filter looks wet in the photo. Is it usually wet or does that only happen when you backwash the filter? If backwashing leaves a wet mess in the pool house you may want to consider switching to a cartridge filter instead.

I was impressed by how good that old filter looks! Fiberglass filters that have spent years in the sun are usually discolored and flaky. The pool house is probably the reason it has lasted as long as it has.

Could you post a picture of any valves to control flow of water to the skimmers and returns? That will help us troubleshoot your flow issues.

 

[MBoz]

Tomorrow afternoon I will gladly post pics (or video?) of the skimmers, valves, etc.

I did try to wipe down the ANTIQUE filter last year. LOL It is located in the pool house. Nicely sheltered, considering our harsh, harsh winters here.

Concerning your inquiry about backwashing, the water is carried thru underground pipes way out to the drainage dish adjacent to the street.
It is only muddy because we had gotten some heavy, heavy rains around the time I took the pics. The filter and pump are actually sitting on large blocks that are off and away from the ground.

So, you said a 300 pound filter is slightly larger than mine? And here I was thinking my pool guy was under selling us on filters. I'm confident in him, really. He just opens and closes the pool for us, and has even tried to talk us into opening it up ourselves! I believe the specs of our TR60 have it 24" around and holding 325 pounds. The one he is suggesting is 27" around and holds 300 pounds. I suppose they are comparable, and he is correct in what he is suggesting.

Oh....and did anyone take note of the pressure gauge reading?! I'm praying the thing is just old and broken. It is off the charts at a reading of 30+ when running.

Concerning chemicals, the pH needs to come into balance before adding liquid chlorine, correct? Muriatic acid is suggested, but will that cure the Alkalinity problem? Or do I have bigger fish to fry at this point?

Thank you all again. I'm confident I can get placed in the right direction soon and redeem the summer!

 

[Teald024]

Hello and Welcome to TFP!! we will help you get things in order.

Cartridge filters are great at not having to dump a lot of water and don't need backwashing. However, all the water from inside the filter gets dumped on the floor/ground when you take the lid off. Unless you can pipe the drain outside of the pump house. Do you have a gravel or dirt floor in the pump house? Also, cartridge filters are very difficult when trying to clean an algae filled pool. Sometime the filter element needs to be cleaned hourly and the only way to do that is to take the top half off and remove the filter element. I'd advise to stay with a sand filter.

If the pressure gauge doesn't go to zero when the pump is off, then the gauge is broken.
Yes, use muriatic acid to lower the pH.
You do not have an alkalinity (TA) problem. the acid will cause the TA to come down some, but that is ok. TA is the least of your worries. You need to get chlorine in the water to prevent an algae outbreak

 

[JamesW]

Your pump is really too big. It's probably using in excess of 2,000 watts.

If you want to stay with that pump, I would recommend a 7 square foot sand filter, like a TR-140.

If you want to go cartridge filter, I would suggest a 400 square foot model.

I would recommend replacing the pump with a variable speed pump.

There are rebates available from some utilities if you switch to a variable speed pump.

If you switch to a smaller pump, I would recommend about 5 square feet of sand surface area, like a TR-100.

 

[Teald024]

@MBoz , can you provide the model of the pump. It is unreadable in the pictures. If you can't find it, how about a picture of the while pump itself. Even though the motor is 2hp, it would be good to know the pump information.

I ask because I had a Hayward Powerflow Matrix pump that had a 2hp motor on it, but it only had a 1hp impeller on the inside. Lets just say that I was very surprised to find that out. Also it looks to be a single speed pump, is that correct?

 

[zea3]

If your pressure gauge goes to zero when it is off and is in the 30s after a backwash and rinse then there could be a blockage somewhere in the plumbing which could account for the poor skimmer and return action downstream.

 

[sktn77a]

Assuming the pool slopes reasonably consistenly, yes, your pool will be ~ 40,000 gal. The pump and filter should be sized accordingly. Your pressure is too high. Either the gauge is bad (most likely) or something is plugged somewhere. I take it you have 1.5" plumbing? Do you have multi way valves controlling the skimmers/main drain and/or returns? How many returns?

SLAM that pool immediately and get the pH down to the low 7s. Get the Ca hardness up too. If you haven't got one already, get a Taylor 2005/2006 or TFP testing kit.

 

[Soupy]

we are in agreement that no amount of chemicals can make this pool usable without a new filter

That's basically dead wrong. Filters don't stop algae from growing. You need to chlorinate properly. Get a good test kit, SLAM that pool, learn how to keep it chlorinated properly, and then worry about filtration.