For those of you with sand blowing back into the pool....

I've learned a great deal in the past week about what can/will go wrong with a sand filter. Many, many times on this forum people have complained about sand blowing back into the pool, and many times we (I) have advised people to go look for a broken or cracked lateral. I will in the future recommend that while looking for a crack in the lateral, that you also check the space between the lateral and the hub they fit onto. There shouldn't be one.

I have just had extensive work and time put into my filter because when it was first installed 6 seasons ago, it was apparently "pieced together" by the installer, and installed in such a way that there was tension on the hub containing the laterals. This caused three of the laterals to have enough space between them and the hub to allow sand through and up into the pipe carrying the return water. The sand got into the joint of this pipe where it connects to the hub, and proceeded to sand down the inside pipe, loosening the fit between the two, allowing progressively more and more sand to be blown into the return water and eventually into my pool.

The only symptom I had was a little sand appearing in the pool the first two seasons, and then becoming progressively more and more until this season, when if I turn the pump off and let it settle, I actually have about 1 - 1/2 inches of sand around the edges of the deep end. Once we figured out what the problem was and correctly installed a new hub and siliconed the pipe back into the hub, the problem is completely resolved. We vac'd it to waste, left the filter running for 2 days straight after that, and for the first time since the pool was built, have NO sand in it.

So--long story short--if you're having recurring problems with sand and don't find a crack or break in your lateral, carefully inspect where the laterals fit onto the hub. That may very well be your problem.

Janet

Great post, thanks!

This will be another thing that I can check as well when I break the filter down.

Now when you refer to the "hub" is that the point where all of the laterals screw into the PVC which connects to the multiport valve (this part rests on the bottom of the tank)? If so where was the space created?

Sorry if the questions sound silly but I am trying to picture exactly where the tension was and what happened.

Thanks Janet!

Yes, it's the part that the laterals screw into, that sits on the bottom...when the laterals are seated in place, there shouldn't be any space between the laterals and the part they're connected to. (Sorry that may not be the best description, but I didn't think to take pics while we had it apart.) Mine were seated in as far as they would go, but it appeared as if they were not screwed all the way in, creating about 1/2" of space between the end of the lateral and the hub, on three of the laterals. Further, The hub has an opening underneath it where the filtered water goes back up into the center into a pipe, and that pipe connects to an L-shaped piece of pipe that goes back out to the multiport valve. It is the connectioin between this L-shaped pipe and the hub pipe that the sand got in between and literally sanded down the inside pipe at the joint, creating space between the two pipes for more sand to enter the return stream.

Does that help?

Janet

Quote:

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Originally Posted by chuck9997

I have the same problem.. with sand.. in a 24foot AG.. I am clueless about tearing down the filter.. and what to look for inside. Are there any pics and/or instructions for filter repairs and maintenance. Is it a BIG job?

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It's really not a big job....we opened the drain plug at the bottom to let the water drain, bled off the air while slowly removing the nut on top and taking the top off....then it's just a matter of scooping sand out of the filter. It would take much less time with a wet/dry vac, but it took me about 45 minutes to shovel 300 lbs of sand into the bucket of my tractor and go dump it. When you get to the bottom and can see the laterals, the whole assembly lifts out. Not a big deal, just kind of messy.

Janet

I've been thinking about this.. and,.. at least for the first time,.. I think I will do as Andy Taylor told Aunt Bee.. I'll: "CALL THE MAN" .. and watch him.

This is my first FULL season with the new 30' AG. I am seeing some sand along the seams quite often.Vacuumed yest. and wa la...today....more sand. Probably only a 1/2 a cup full. Not much, but annoying. A friend of mine told me not to back wash as often, as it makes the sand "more sticky". This didn't sound too intelligent, AND I don't back wash every single week. My pool doesn't have many people in it often, and at that not many kids. I backwash about once every 3 weeks. I know I know....but it's looked good since day 1.

Anyway, I don't assume I have a cracked lateral, and probably have a lateral head with some "space". The filter was already assembled when they installed, so I guess I have to wait till I close the pool in order to "check this". Sounds like a good plan, but I guess I can deal with the sand till mid sept when we close.......

I just can't imagine how to do all that with the pool still open? Plus, I would rather try and wait and just kill two birds w/ one stone and change the sand next season. I know that with Chlorine, they say every 3-5 years, but whats $30 or so to ensure sparkling water w/ fresh sand eh?

Anyway.....keep this post going. Very educational....and with all my jibberish, can someone post me back?

An idea would be for someone to go to say the website of a filter, screen shoot the diagram of the lateral heads, and describe based on what the diagram shows. Just a thought.

http://www.sta-ritepool.com/pdf/S260EN(6-3-03).pdf

Maybe going to this site and going to page 6 will help you check your laterals. It helped me understand. Now my only ? is ....how to do it during the swimming season..or is it not possible?

All you have to do is turn off your shutoff valves (this would be one of the many reasons to have installed shutoff valves), and your pump and filter will be completely isolated from the pool, allowing you to perform a complete teardown of the equipment if need be. If you did not install shutoff valves, you can try blocking the skimmer hole and return with rags, but you WILL lose some water this way because it will wick through slowly.

What about fastening the skimmer plate over it? That would block out most of the water. And you can put an expandable rubber plug in the return to close it off.

Anna

New versus old laterals. Slightly different models, as I have an older Triton from the 80's as opposed to the current Triton II.
Attachment 951

I suppose this could have happened before I was putting the laterals in, but I think I overtightened the laterals, and... CRACK! There goes the hub... :(
Attachment 953

New hub and old hub. Too bad they don't attach the same, but the parts are damn similar for a Pac-Fab Triton from the 80's, versus a current Pentair Triton II.
Attachment 958

Here's what a groove created by sand looks like. This must be the culprit to where sand was blowing back in, though the entire web of lateral spokes were cracked long before I got into the filter yesterday. The spots where it cracked show some aging and wear, as if they'd been there for a while.
Attachment 959

I believed that my filter was blowing sand, but it was particles my filter was not picking up. I started adding DE to my filter and it has had tremendous results. I followed the recommendations on this site.

Nothing like a cheap, simple fix! DE as an add-in to a sand filter and skimmer socks are my two favorite cheap fixes.