Sand filter question

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RobbieH

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Aug 30, 2010
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Dallas, TX
Is it normal for a sand filter to blow sand out the returns when the pump starts up? I get four nice brown clouds every morning whent the pump starts up. I do keep the system backflushed.

I believe the sand filter itself could be 15+ years old, but no way to tell for sure, and no way to know if it's ever been refilled.

Also, at the top of the filter, should the clear dome have water percolating along with air, or should it be smooth, just water? I can get photos to illustrate what I mean if it would help.
 
Thanks for the quick reply!

Great. Well, I guess that can go on my list of items to deal with. Was hoping most of this could hold out until after pool season was over when we get the plaster redone.

Now I have to decide whether to stick with sand or change to something else.

Note my addition to the percolating in the clear dome.
 
The percolating in the dome can be caused by a small air leak on the suction side of the plumbing, you'd also have an air bubble in the pump housing that just won't go away :(

It'd be optimal to not have the bubbles in the filter dome or pump, but that's an issue you can deal with at your convenience after the sand problem is dealt with :)
 
I had a leak company out in the fall and they could not find any leaks in the plumbing. They did a very thorough job on both the pressure and suction side. I had a very pesky leak in the plaster at the tile line, which they were able to temporarily resolve with epoxy.

I still believe (as you do) I have an air leak. I can release the air and it will stop percolating for a while, but in about an hour it returns.

I have considered the air might be coming in around the lid for the pump filter/strainer. When I shut off the pump, water squishes out around the o-ring. I keep the ring lubed, so not sure what else I can do there other than replace that part and see if it is the culprit.

Guess I'll be tearing down my sand filter to see if the laterals are bad.
I found the manual for the filter, it was installed 6/15/1986. Guess I was a little off on the age of the filter! It's a Pac-Fab Triton model TR-100, guess that shows its age, huh?

The manual just says the sand is removed by removing the "sand drain assembly". I don't see that on the schematic. Any idea what the proper way would be to remove the sand?

I have attached some pics to show some of the equipment. You can tell where the leak detection company cut the PVC to test all the lines. Those lines that aren't PVC are copper. This is an OLD pool.

dome.jpg


plumbing.jpg
 
Hey, I have another question... I just read in another thread that I should wait 30 seconds before going from backwash to powering the pump back on in normal mode. When I had a pool guy show me how all this stuff works, he never mentioned the wait. I also see it in this manual I found. Could it be me not waiting to fire the pump back up is causing sand to go into the returns? Could this have damaged the laterals? I can't think of anything else that might have caused the laterals to be damaged.
 
Wow, someone else has the same ancient filter! Mine was also installed in '86.

I've got one TR-100 and two TR-140s at work. The 100 always "percolates" like you said, and requires air bleeding frequently. I think in my case it's because there's a flexible coupling before the pump that might have a tiny leak (though it doesn't leak from here when the pump's off though so it might not be the issue). Another place to look is the pump basket o-ring, make sure it's in good shape and lubricated.

As for the sand, does your pump shoot sand every time you start it, or just after backwashing? The sand drain is the plug on the underside of the tank, usually you can take out the small plug and drain just the water, or the whole plug and wash the sand out. I usually just shop-vac it all out.
 
Turning the pump back on quickly after backwashing is not related to the problem, nor would it cause any damage. That rule has to do with allowing the sand bed to settle gradually so it will filter better.

Another thing to check, if the water level is a little too low, a vortex can form in the skimmer, drawing in some air along with the water.
 
I know that o-ring leaks around the pump basket o-ring when I shut the pump off. I'm just going to go ahead and get a new o-ring tonight since I need a new pump basket and skimmer basket anyway.

The sand is much worse just after backflushing, but it does it every time.

My pool water level is not low. It's halfway up the skimmer throat.

When the water is percolating, I get some bubbles out the returns in the pool too. If I bleed it off, the bubbles stop.

Since you have one of these, do you know if the laterals for the new TR-100s are the same as this ancient one? If I can get the replacement part, I'm looking at a whole lot less money than a whole new filter.
 
RobbieH,

Have you verified that it is sand?

Sand should not really be a "cloud" but should fall to the pool floor rather quickly.

Do you have gritty sand on the pool floor in front of the returns? Make sure it is gritty by picking it up between your thumb and fingers.
 

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RobbieH said:
Since you have one of these, do you know if the laterals for the new TR-100s are the same as this ancient one? If I can get the replacement part, I'm looking at a whole lot less money than a whole new filter.
Click to expand...

I believe the laterals are the same. I get my parts from In The Swim and they don't make a mention of a newer version, however there are a couple different sizes, ones for the 100 and other larger ones for the 140 and up.

Make sure it's your lateral before buying one. I thought I had a broken lateral in our outdoor spa one time due to some unexplained sand, but after inspecting them I never saw one broken. I changed the sand and haven't seen any sand since, I never found out what was going on. I'd hate to have to change one, a hard tank to maneuver around in.
 
I'm 99% sure it is the sand. The cloud is exactly the same color as the sand in the filter. Could it be that 25 years of filtration has worn out the sand to the point it's so fine that it blows off?

Once I get my pool cleared again (clearing winter algae right now) I'll get a photo of what it looks like at start-up. The pool is too cold for me to get in it to feel around the bottom right now, and the robot usually cleans it all up anyway. I could do the sock test and catch some of the blowoff from one of the returns.
 
I'd check out the o-rings inside your slide valve before checking the laterals. They dry out,crack,or stretch out of shape and can cause the problems you described. Often when they go bad the valve is hard to move or won't go all the way down. Also,they will drip out the backwash line. Good luck.
 
and the robot usually cleans it all up anyway
Click to expand...
That makes it easy. You should be able to find grains of sand inside the robot's bag.

No, the sand has not worn down into powder.

If you have not found sand inside your robot, the problem is algae inside your filter and it's a cheaper, perhaps even easier fix
 
I've seen a similar problem when the o-ring on the up-pipe from the laterals has gone. When the pump is off the dirty water rises up off the sand bed into suspension. Then when the pump is turned back on it draws some water through the broken o-ring from the dirty side of the filter sending a small cloud of dirty water into the pool. Once the the pump has run from a moment the dirt is back in the sand and not-so-dirty water is in the area above the sand bed. This is always worse after a back wash for obvious reasons.
 
What the robot is picking up mostly right now is a grey slimy stuff, which I"m 99% sure is the dead algae from me just completing the shock process. Honestly, I haven't seen sand as far as I remember in the robot (it just died for the second time... so right now I have no robot). So now I'm thinking it's not sand blowing out, although it is the color of sand. I have a pool expert friend coming over Tuesday to watch it start up, hopefully he will be correct on what the problem is and we can get to the bottom of the problem.

I am very curious to know what the solution is for algae inside the filter, because this is not something that crossed my mind.

Thanks!
 
Already went through that process. It took me a week to get through the entire process. The issue was there before needing to shock, and hasn't gone away since completing the shock process. That's what I get for going on a trip and asking someone to do something as simple as add a bottle of bleach to my pool every day; came home to a green pool and an "I forgot". My CYA is almost zero (yea I know, working on that, there's a reason I'm not raising it quickly) so the shock level only had to come up to 12 (I hit 14 anyway) and as I said I held it there for a week until finally the overnight chlorine level stabilized. Water is clear except for the cloud caused every morning when the pump fires up. Takes a while for that to all settle back out, and it reclouds if I sweep or run the (now broken) robot. So, it's sounding like algae is not my issue.
 
I'm pretty sure if the resolution to algae is shock.

I did find my air leak yesterday. The filter is now filtering away without percolating. If you look in the second picture you can see a black hose going into the bottom of the pump basket housing. That hose goes up to a hose bib, I am assuming for priming the pump or filling the system without needing a separate hose. I found the hose bib was leaking around the valve, allowing air to draw into the system. I replaced the hose bib and no more air.
 

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