Sand Filter needs backwashing OFTEN, could i have gunk?

plsbcheap

Well-known member
Jun 24, 2007
75
#1
I have a new pool finished in about August/September. It had two big leaks and was loosing a lot of water every day. The builder would not return to fix the leaks since he had final payment. He thought I was an idiot who could not measure water loss and kept blaming it on evaporation. He is not a reputable or ethical guy at all. :twisted: After a several months of waiting on him I turned off the pumps and let the pool sit thru the winter since I was spending so much money on water to refill. Finally in March/April I hired a leak detection company to find and repair the leaks, put the chemicals back and start enjoying the pool. I realize it was something I should have “bit the bullet” and hired out when it first happened.

I tell you all that to say the pool obviously got green and gunky. In the early months of having the pool the filter never needed backwashing. I only remember it being done once in the fall since construction was complete.
When I finally got the pool clean and restored the filter seems to get dirty really fast and need backwashing every few days. I back wash when the pressure goes up and I actually notice the return have very little to no water coming out into the pool. My pressure goes up and the flow goes to zero it seems.

I have a Pentair Triton II filter with sand. My pipes are oversized according to the builder. He said he “uses 2” instead of 1 ½ for better flow” and my pump is a Pentair Intelliflo 4x160. This pump is adjustable for RPM’s so the flow can be controlled.

After a backwash cycle the water really ripples coming out of the returns on the lowest pump setting. After a couple of days you can not see OR feel the water even coming out of the returns. When I backwash it immediately gets back to normal.

QUESTIONS:
1)Why is the filter getting dirty so fast? I have nothing around the pool to dirty the water and the water is really clear.
2)Could the filter have some gunk/algae/funk that is not really washing out on the backwash cycle?
3)Is a chemical cleaning of the sand needed? What product to use, how?
I am enjoying this site. A LOT TO DIGEST!!!
Thanks,
Dwight
 

Rangeball

Well-known member
May 25, 2007
785
#3
Back when I had sand and relied on the pool store, I would have issues like this. Finally broke down the filter and found there was a 3-4" layer of dark green sand on top, an algae colony that I couldn't kill back then not knowing what I know now.

Can you post a complete set of test #s? Maybe you just need to shock, hold it there for awhile then perhaps it will backwash?

My remedy then was to change the sand. Not a fun job, but it worked.
 

KurtV

LifeTime Supporter
Mar 29, 2007
270
SE Louisiana
#4
I think rangeball is probably in the ballpark. Just last Saturday, I popped the top off my sand filter (also a Triton II) tohave a look-see. I backwashed and rinsed it first and then shut off the pump, popped the top, and allowed the filter to drain down. Even though the filter medium wasn't crusted over or visibly dirty, I found quite a few "hairballs" as far down as 4-6 inches into the sand bed (zeobrite actually). I pulled all of those out that I could, replaced the top, backwashed again to stir things up, and repeated the manual cleaning. All in all I probably removed a half-gallon or so of the furry stuff . I don't think the "hair" was having any adverse effect on filtering or flow (normal filter pressure and flow before and after the manual cleaning) but I imagine that with time that stuff would have continued to accumulate and would have eventually resulted in a condition similar to yours where the filter clogs quickly.
 
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plsbcheap

Well-known member
Jun 24, 2007
75
#5
I do backwash for 2-3 minutes and rinse usually 30-40 seconds. It is very clear. It usually clears in about 45 sec to 1 minute in backwash.

Chlorine 3
Salt 3200
PH 7.8
Total Alk 120
Calcium Hardness 160
CYA 100

The only thing the pool store suggested was Hardness increase of 15 lbs. After reading on here about not needing Calcium in vinyl pools I may not add that any more. I do have some water falls from the spa that i expect will leach and scale from the mortar if i leave it out though. I have not decided yet.

Rangeball, You said you had "a 3-4" layer of dark green sand on top, an algae colony that I couldn't kill back then not knowing what I know now." Knowing what you know now what would you do instead of changing the sand? Should I open the top of the Triton II and look inside? I am looking for sludge that isn't washing out?

Thanks guys,
Dwight
 

Rangeball

Well-known member
May 25, 2007
785
#6
plsbcheap said:
Chlorine 3
Salt 3200
PH 7.8
Total Alk 120
Calcium Hardness 160
CYA 100


Rangeball, You said you had "a 3-4" layer of dark green sand on top, an algae colony that I couldn't kill back then not knowing what I know now." Knowing what you know now what would you do instead of changing the sand? Should I open the top of the Triton II and look inside? I am looking for sludge that isn't washing out?

Thanks guys,
Dwight
Dwight, I assume that's free chlorine and you have a SWG? This would make sense as to why your water is clear, any algae coming out of the filter is most likely getting toasted as soon as it hit's the cell. If you don't have SWG, then with your CYA you likely need more FC.

Yes, if I were you, I'd open the filter and have look see. Mine was dark green, like the color of spinach, that would not break loose and backwash out. If yours is similar, I would be tempted to do one of a few things-

1- Shock the pool with bleach to the level indicated on the best guess chart, I think for 100 CYA it's 25 ppm but check for sure. Monitor the pool to maintain this level for awhile, backwashing the filter frequently.

2- Drain the water from the filter, close the filter from the return and supply lines and fill with water and add enough bleach to get to the shock level and let it sit for awhile, then add more bleach, etc. The only thing that I'd be cognizant of is exposure to high levels of bleach can make plastic brittle over time. Hopefully this would kill the algae quickly so you could fire things back up and backwash it out.

3- If algae is present, I would scoop out as much of the affected sand as possible assuming it's only a few inches worth, add new sand then do 1 or 2. If the sand appears in bad shape, I'd do a total sand exchange. After what it sounds like your pool looked like, I'd probably just do this, shock and be done, hopefully.
 

JohnT

Admin
Mod Squad
TFP Expert
Apr 4, 2007
9,468
SW Indiana
#7
Rangeball,

(sorry if this is a minor derail, plsbcheap)

Your post makes me wonder about something. I can't imagine anything green in there but algae, but algae can't grow without sunlight. Is it possible the algae was in the pool but not at a level that was visible, and the filter was just collecting it? Or could dead algae have collected in there, and without sunlight, it didn't fade to gray?

Since I'm already in derail mode, I wonder how long algae will survive without sunlight? Thinking I could roll black plastic over my winter cover for a couple of days before opening in place of the chlorine regime. I may go Googling tonight.
 
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plsbcheap

Well-known member
Jun 24, 2007
75
#9
Rangeball said:
I assume that's free chlorine and you have a SWG? This would make sense as to why your water is clear, any algae coming out of the filter is most likely getting toasted as soon as it hit's the cell. If you don't have SWG, then with your CYA you likely need more FC.

Yes, if I were you, I'd open the filter and have look see. Mine was dark green, like the color of spinach, that would not break loose and backwash out. If yours is similar, I would be tempted to do one of a few things-

1- Shock the pool with bleach to the level indicated on the best guess chart, I think for 100 CYA it's 25 ppm but check for sure. Monitor the pool to maintain this level for awhile, backwashing the filter frequently.

2- Drain the water from the filter, close the filter from the return and supply lines and fill with water and add enough bleach to get to the shock level and let it sit for awhile, then add more bleach, etc. The only thing that I'd be cognizant of is exposure to high levels of bleach can make plastic brittle over time. Hopefully this would kill the algae quickly so you could fire things back up and backwash it out.

3- If algae is present, I would scoop out as much of the affected sand as possible assuming it's only a few inches worth, add new sand then do 1 or 2. If the sand appears in bad shape, I'd do a total sand exchange. After what it sounds like your pool looked like, I'd probably just do this, shock and be done, hopefully.
Yes I have a SWG, it is an Intellichlor. My FC is going up and down but I had 10 little boys on Tuesday and 14 girls on Thursday for swim parties. I would expect that many swimmers will hammer the FC down to "1". I will run a SUPERCHLORINATE cycle this week and check it again on Friday. Then I will also open the filter and see what is in there. I have never looked inside before. Any thing I need to be aware of before opening? I assume you will cut the power to the pump, turn the incoming Jandy valve to block off any water coming in and put the Multiport or "closed". Anything else? After I see what is inside I will post it, maybe a picture too!

#1- You said to "Shock the pool with bleach to the level indicated on the best guess chart, I think for 100 CYA it's 25 ppm but check for sure." What is the "best guess chart" and are you saying to add regular bleach as indicated on the forums to replace expensive "shock"? Where does it tell me how to equate the amount used?

Thanks guys,
Dwight
 

KurtV

LifeTime Supporter
Mar 29, 2007
270
SE Louisiana
#11
plsbcheap said:
Yes I have a SWG, it is an Intellichlor. My FC is going up and down but I had 10 little boys on Tuesday and 14 girls on Thursday for swim parties. I would expect that many swimmers will hammer the FC down to "1". I will run a SUPERCHLORINATE cycle this week and check it again on Friday. Then I will also open the filter and see what is in there. I have never looked inside before. Any thing I need to be aware of before opening? I assume you will cut the power to the pump, turn the incoming Jandy valve to block off any water coming in and put the Multiport or "closed". Anything else? After I see what is inside I will post it, maybe a picture too!

#1- You said to "Shock the pool with bleach to the level indicated on the best guess chart, I think for 100 CYA it's 25 ppm but check for sure." What is the "best guess chart" and are you saying to add regular bleach as indicated on the forums to replace expensive "shock"? Where does it tell me how to equate the amount used?

Thanks guys,
Dwight
Dwight,
After you shut down the pump, just unscrew the closure on the top (the supplied wrench is probably on it) and then rotate the diffuser out of the way and have a look and feel in the sand. Check for a crusty top layer and for stuff embedded in the top few inches of the filter media. If it's crusty, you can put a garden hose in there to help you stir up and break up the junk. Backwash and repeat the procedure after that until you have a nice, fluffy sand bed.
 
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plsbcheap

Well-known member
Jun 24, 2007
75
#12
UPDATE on sand filter problem, HELP

Okay it was last summer when I posted this topic. The water was clear the rest of the summer and I decided not to open up the Triton II sand filter. This year (about 3 weeks ago) I started getting algae build up when the weather warmed up. I shocked and got the chlorine # up to 2.5 but it soon went away. My last water test showed 0 stabilizer. That tells me why my chlorine is vanishing even though I have been hitting my "superchlorinate" feature every 4 or 5 days. So I have purchased 9 lbs of stabilizer (Cyanuric Acid) to put in hold my chlorine. I also had no salt so I added about 10 bags of salt. Oh the reason I think my stabilizer/salt is gone, My wonderful pool builder made several boo boo's that cause leaks. I begged him to find them and fix them and he kept saying it was not leaking and my imagination. His fix is always to put an "autofill" valve on pools and you will never know. I had the liner scanned and found a few holes but the light niche conduit was broken and the main problem. My guess is that over time the stabilizer and all other chemicals were disappearing. Maybe the Cyanuric Acid dilutes and disappears over time too. I don't really know but I don't think Salt or CYA evaporate like chlorine does.

Soooooo, before I add the CYA ($30) to the filter/skimmer, I decided to open up the filter and take a peek since it still seems like it needs backwashing pretty often. The picture shows what I saw sitting on top of the sand. It is squishy like sponge. I have no idea what it is. We had a HEAVY pollen season so the yellow looks like pollen. The rest is kind of bound together and clumpy. I took my wife's strainer basket from the kitchen (Uh oh) and scrapped across the top of the sand and shook the sand through the strainer. The next photo shows the pile of junk.

Questions:
Should I do anything else like pour bleach, shock what in the filter and try to kill this?
Should I add sand now? How do I know the right level of sand?
Why won't this **** wash off the top of the sand in the backwash cycle?



 

duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
31,398
Sebring, Florida
#13
Re: UPDATE on sand filter problem, HELP

Questions:
Should I do anything else like pour bleach, shock what in the filter and try to kill this?
Should I add sand now? How do I know the right level of sand?
Why won't this **** wash off the top of the sand in the backwash cycle?
pls,

Your pool is suffering desperately from lack of chlorine. Let me answer the three questions above and then suggest a path to follow....

A. Absolutely....you have to shock your pool....forget the "superchlorinate" mode of your SWG...it wont do it.
B. Assuming you don't have a manual, Triton's tech support will tell you how much "freeboard" is required for your filter...normally, the sand comes up in the filter about 2/3's.
C. Too much time going without proper chlorination. Clean it up manually (scoop it out) and we'll help get you set up so it will never form again.

Okay, here's the path.....Please post a set of current test results to include FC, CC, pH, Alk, CYA and CH. That'll give us a starting point and directly influence what advice is given from that point.

Secondly, get some Clorox....lot's of it....maybe 30 gallons. You will not waste any of it and your SWG is not capable of producing the amount of chlorine required to truly shock your pool and get it all cleaned up.

Post those numbers up and we'll all help (welcome back! :lol:
 

Denali

Well-known member
May 1, 2008
70
#14
When you backwash are you changing the flow rate of the pump? I would think you want it on high flow for best backwashing. If you're doing that then nevermind. :)
 
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plsbcheap

Well-known member
Jun 24, 2007
75
#16
Okay thanks guys. Here is the test results from 4 days ago. I can go to the pool store today and get the water checked again.

FC=0.5
CC=don't know how to get this
pH=7.8
Alk=120
CYA=0
CH=140
Phosphates=100
Salt=3000


Is this gunk just on top of the sand so after I scrap/sift out the top then I'm good or do I back wash again and scrap again? Does this **** come to the top of the sand during back wash? How do I know how deep that stuff is in the sand? BTW, my sand appears to be at least 2/3 up in the Triton II. I think it is about where the line comes in from the multiport (on the right).

Should I just use the granual shock 1lb packs? It seems like that would be cheaper than 30 gallons of bleach. I need to check the prices again but I think a 1lb pack of shock is about $3.25 per lb. I don't know how many or how strong is needed the package says that 1 lb per 12K gallons is all that is needed but you may want me to do something else. Regular Clorox is probably about $3.50 for a gallon. There is also the "Outdoor" Clorox that is about $5.50 but it doesn't tell you the strength on the bottle.

Denali, I do run the pump on high speed for the backwash and rinse. I try to go 2 min on backwash even though the water looks clear at 1 minute. It is an Intelliflow 4x160 so I think it is running at 3500 RPM's.

BTW, my water looks okay from a clarity standpoint. I had a party on Monday so I wanted it to look clearer. After I threw in the 1 lb. pack of Shock Plus it really looked pretty good. But obviously with no CYA I didn't stay clear all week. Thanks.
 
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plsbcheap

Well-known member
Jun 24, 2007
75
#17
Sand Filter needs backwashing OFTEN, i have gunk How 2 rid?

my water is looking much "greener" today. Getting cloudy. Oh and the Clorox was $4 for a 1.42 gallon jug at HomeDepot. Still that is going to cost about $85 for 30 gallons. Is that the best way to do it? Is the "outdoor" Clorox much stronger and/or is it cheaper to shock with the "Shock plus" powder?
Thanks,
Dwight
 

duraleigh

Admin
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In The Industry
Apr 1, 2007
31,398
Sebring, Florida
#18
plsbcheap said:
Okay thanks guys. Here is the test results from 4 days ago. I can go to the pool store today and get the water checked again.

FC=0.5
CC=don't know how to get this
pH=7.8
Alk=120
CYA=0
CH=140
Phosphates=100
Salt=3000


Is this gunk just on top of the sand so after I scrap/sift out the top then I'm good or do I back wash again and scrap again? Does this **** come to the top of the sand during back wash? How do I know how deep that stuff is in the sand? BTW, my sand appears to be at least 2/3 up in the Triton II. I think it is about where the line comes in from the multiport (on the right).

Should I just use the granual shock 1lb packs? It seems like that would be cheaper than 30 gallons of bleach. I need to check the prices again but I think a 1lb pack of shock is about $3.25 per lb. I don't know how many or how strong is needed the package says that 1 lb per 12K gallons is all that is needed but you may want me to do something else. Regular Clorox is probably about $3.50 for a gallon. There is also the "Outdoor" Clorox that is about $5.50 but it doesn't tell you the strength on the bottle.

Denali, I do run the pump on high speed for the backwash and rinse. I try to go 2 min on backwash even though the water looks clear at 1 minute. It is an Intelliflow 4x160 so I think it is running at 3500 RPM's.

BTW, my water looks okay from a clarity standpoint. I had a party on Monday so I wanted it to look clearer. After I threw in the 1 lb. pack of Shock Plus it really looked pretty good. But obviously with no CYA I didn't stay clear all week. Thanks.
If it were my pool.......

1. Clean the gunk out of your sand filter. It's probably 95% right on top but dig down a few inches and "fluff up" the sand and relevel the bed. that'll do it.

2. Add some CYA. Using Jason's calc in my signature, add enough to get to 30-40ppm. it'll take a while for it to dissolve so get it in soon. Don't put it in your skimmer. Suspend it somewhere in your pool in an old sock so it'll dissove slowly into the pool water.

3. This evening, after the sun is off your pool, use jason's calc and bring your FC up to 20ppm. It's fine to use the bags of shock as long as you calculate the amount correctly and be sure you put in enough to get to 20ppm. You can use both clorox and powder.....poured into the skimmer at different times.

4. Here's the trick......you must KEEP YOUR FC AT @20ppm UNTIL YOUR POOL IS CLEAR. To do that, you will have to re-test and add more chlorine at least twice daily and more often if you have time.

5. Shop somewhere else. Most of use pay around 1.90 or so for the jugs of clorox you're talking about.

6. This is a process....not an overnite event that will magically clear your pool....probably gonna take a few days.....much longer if you don't keep the FC up @ 20ppm.
 
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plsbcheap

Well-known member
Jun 24, 2007
75
#19
I will go to the store now and recheck the water before I start. BTW, What is mustard / yellow algae? Can you tell from my photos if that is algae and mustard algae? Is it harder to kill? Does it really matter? I just see several references on this site to mustard algae but didn't see an explaination.

your #2) I thought I was suppose to add it to the skimmer? I don't want to backwash at all after I start this right? Won't I loose the CYA?
#3) put the bleach in the pool and not in the filter? Keep it running over night? or shut if off, what?
The pool water actually looks okay it is the concern with all the junk on top of the sand I was wondering about. I mean I don't have a swamp here but I appreciate the help because I want to avoid bad water which may be on the way. Also, I assume NO swimming for a while.

I'll need 9 lbs of CYA to get it to 40. So 3 socks full of CYA at once floating around in the pool? None in the skimmmer?

I don't understand the difference in all the choices from the calculator....
add x of 6% bleach. Jug size 96 oz 128 oz 182 oz. okay with this on
or add by weight or by volume of trichlor, dichlor, cal-hypo 48%, cal-hypo 65%, cal-hypo 73%. 5 choices of chemicals?
Note: Dichlor and trichlor add CYA and lower PH. Cal-hypo adds CH. (does this mean if I put in Dichlor and trichlor it will raise the CYA and lower PH? and Cal-hypo adds Calcium Hardness? My CH is only 140. From something I read in the past on this great forum I believe most don't worry about CH for a vinyl pool. Is that right? What should I use? Thanks,
Dwight
 

billyjoeraybob

LifeTime Supporter
Apr 9, 2008
50
SC Midlands
#20
plsbcheap please do yourself a favor and get yourself a good drop based test kit. Either the TF-100 from www.tftestkits.com or the Taylor K-2006. There is no substitute for accurate testing. You can't rely on the pool store. Once you get a kit post your numbers and we will help you get a a beautiful sparkling clear pool in no time.