Intex Sand Filter/Pump Slowly loses flow

[PieterS]

Hello - new to the forum, looks like lots of great advise here! I set up a new 16'x48" intex pool this year with the included 1200GPH sand filter/pump combo. I am using a SWG in line with the pump. My problem is that the pump will start out good and strong after backwash/rinse, but after several hours loses enough flow to shut down the SWG, and the little aerator on the return line no longer aerates due to low flow. The pressure on the filter is barely going up, maybe a psi or 2 to go from 'high green' to barely touching the yellow - but yet I have low flow through the SWG and into the pool.
The water is not crystal clear - chemistry is mostly balanced, although it is running high on hardness. The SWG seems to be maintaining enough free chlorine. I tried running the SWG in 'boost' mode overnight - but it shut off sometime during the night due to low pump flow.
If I backwash/rinse - it'll run fine for a little while - but gets bogged down again after several hours.
What am I missing?

 

[mknauss]

Welcome to the forum!
The majority of the time, this issue is due to chemistry, not equipment.
Can you post a full set of pool water chemistry test results from your own test kit?
I suggest you read ABC's of Pool Water Chemistry.

 

[PieterS]

Thanks - some useful stuff here! I"m suspecting too that chemistry might be a big part of it - but surprised the filter pressure isn't rising more than it is yet flow is reduced so much??

I will test the water around lunchtime and post results. I know hardness is high (filled with non-softened water, I know my water is hard!) and pH is running up near 8.0. I"m only using test strips so far and getting frustrated with interpreting them! I'll poke around a bit and see what folks here prefer for testing.

 

[mknauss]

You need to follow the SLAM Process. To do that, you need a proper test kit. I suggest the TF100. A proper test kit is needed to get the accurate water chemistry results needed to follow the TFP protocols.

 

[PieterS]

Makes sense - just tried testing with the strips and it's frustrating - hard to interpret, and sometimes conflicting results depending on the strip brand I use! If I sort of average them out - I get
TC 3
FC 3
pH anywhere from 7.6 to 8.4
Alk 180-240
CYA 50-100 (strips don't have sensitivity for this!)
TH 500+

I'm hesitant to make too many changes based on these strips and just ordered a K-2006 complete test kit. I'll get a good read then and go from there.

 

[PieterS]

Received my test kit and tested the water yesterday. I initially read:
FC 7.8
CC 0.4
pH 8.0
TA 250
CH 180
CYA 30

I added pH minus yesterday and more stabilizer. Stabilizer has not dissolved yet, but checked pH and TA today:
pH 7.6
TA 230

So a bit more work to do on TA! Will plan to bring pH down a bit more and then re-check. Also backed off on the SWG a bit to let FC float down a bit.

 

[Ronkivxx]

Hey there- I have a Coleman (Intex) 18' pool that came with a pathetically usless cartridge filter and after reading a bunch on this site, I decided that I needed to get a sand filtration system. I ended up getting the intex 2800GPH, which is basically the same thing as yours (with more GPH, obviously). I researched the Intex filter/pump quite a bit before purchasing it and I ended up buying an extended warranty on it because from what I read if you get a good one, the Intex is a GREAT pump/filter system but there seem to be quite a few lemons. I have even seen it said that there's something wrong with the QC testing at Intex, the problems are so common.
Reading people's reviews/complaints and experiences, one VERY COMMON complaint was exactly the behavior you are experiencing. Sometimes it would happen out of the box, other times on the second or third year of use, after working perfectly up until then (the very reason I decided to get an extended warranty).
I can say that my intex DOES NOT do this at all, and has great flow anytime it is running. I run it for 6 hours a day.
Think about it; if your pressure is not abnormal and you lose flow, what else could the problem be but in the pump somehow? Meaning, I do not think that the problem is likely due to your chemistry. HOWEVER, most of my limited pool knowledge comes directly from this forum, so if someone here disagrees with me, they're probably right. I just happen to have experience with the Intex.

Edit: I almost forgot; did you follow the procedure for setting up and running your filter/pump for the first time as outlined in the manual? I have seen a number of people say that if you do NOT follow it to the letter, improper operation such as you are experiencing can result. Take that with a grain of sand though because people say a lot of things they have no idea about sometimes.

 

[PieterS]

Thanks for the response. I don't recall exactly - but I did read the manual and think I set it up as specified... One puzzling thing is that if I switch the valve to 'recirculate' once the pump slows down - I do get good flow from the pump (I'll try to verify that one more time). So that seems to imply it's something in the sand filter that is fouling up pretty quickly? I still think I would see a pressure spike if that happens though? I guess if my 'clean' pressure is only about 5 psi - and then it creeps up to 6 psi - that's still a 20% increase, and backwashing is recommended at 25% increase.

If/when I get the water chemistry just right, and this is STILL happening, I'll blame the pump more. It does seem like the Intex pump/filter system is a pretty good value if it works right. I may just decide to size up to the next bigger Intex pump next year, depending on how the rest of this year goes. It's good to hear that your higher throughput pump (on a bigger pool) does NOT seem to do this. It's also a bit clunky interface on how you can't just set a timer and then bypass it for backwashing or vacuuming - as soon as I want to do either of those - I have to sync the pump again with the SWG - a bit annoying.

 

[Ronkivxx]

That's weird about getting good flow when switching to recirculate- I would think that would imply that the problem is somewhere in the sand filter as well. However, as you said, I would also think that would show itself in the pressure.
I looked your specific pump up out of curiosity and I did notice in a comment someone said that with their 16' pool it had low output and that they had to run it almost 24 hours for it to work properly. I have a sneaking suspicion that perhaps their pump does what your pump does and they've just never seen it running properly.
I don't know what you mean with the interface being clunky; it looks like the same interface as mine and mine basically ONLY works in the way that you say you wish your pump did. Basically I turn it on and set it for how many hours I want it to run and it will then do the same thing at the same time the next day. To backwash I just turn it off, set the lever to backwash, turn it on, backwash, turn it back off, set the lever back and turn it back on. Truth be told, I don't even know what you mean when you say you have to sync it. Maybe it's an older interface and there's something screwy with that?

This might seem obvious, but perhaps you didn't use the right kind of sand? I do not have a lot of experience with these pumps (yet!) but I would think that having the incorrect sand might also possibly cause your problem.

Additionally, if you happen to be reading this, I have a question for mknauss. You said that the majority of the time, this issue is due to chemistry. I've seen your posts everywhere on this site and so I'm pretty much willing to take whatever you say as gospel. From what you said, it sounds like this is a problem you are familiar with so I was just wondering if you could explain what about and how the chemistry could cause this problem. Just interested and trying to learn.

 

[jseyfert3]

Sounds like the filtwr getting plugged. The one on mine can do that very quickly. It can be fine for days if nobody is in the pool, but a bunch of people getting in and out tracking in dirt and I literally had it go to almost no flow in a matter of hours.

A quick backwash foowed by a quick rinse and all back in order with normal flow.

For me I started at ~9 psi and get almost no flow at ~11 psi, just barely in the yellow.

My key point is if a backwash/rinse cycle drops the pressure and restores flow, the sand was clogged and it's not a pump issue, no matter how much pressure rise/drop there was before/after.

 

[PieterS]

I don't know what you mean with the interface being clunky; it looks like the same interface as mine and mine basically ONLY works in the way that you say you wish your pump did. Basically I turn it on and set it for how many hours I want it to run and it will then do the same thing at the same time the next day. To backwash I just turn it off, set the lever to backwash, turn it on, backwash, turn it back off, set the lever back and turn it back on. Truth be told, I don't even know what you mean when you say you have to sync it. Maybe it's an older interface and there's something screwy with that?

This might seem obvious, but perhaps you didn't use the right kind of sand? I do not have a lot of experience with these pumps (yet!) but I would think that having the incorrect sand might also possibly cause your problem.

Ronkivxx - thanks for the dialogue. I probably wasn't clear enough - I have this in-line with a salt-water cell for my salt pool. So that cell depends on the pump running for it to work - and the two don't communicate. So I have to make sure that the pump runs at the same time every day so that the SWG can do its thing. When I start the pump OUTSIDE that schedule to either backwash it or to vacuum the pool, I was assuming that now messes up that schedule (the pump will now start at that NEW time every day when I started it up to vacuum or backwash. Maybe that's not true?)

I do think I have the right sand in it. Per the other reply - this bottom line pump/sand filter just seems to foul up pretty quickly. A quick backwash does restore things - but it's frustrating to have to backwash that frequently, seems like I shouldn't have to. I think mknauss was implying that whatever may be off with the water chemistry is producing particulates that are fouling the sand filter quickly.

 

[PieterS]

Sounds like the filtwr getting plugged. The one on mine can do that very quickly. It can be fine for days if nobody is in the pool, but a bunch of people getting in and out tracking in dirt and I literally had it go to almost no flow in a matter of hours.

A quick backwash foowed by a quick rinse and all back in order with normal flow.

For me I started at ~9 psi and get almost no flow at ~11 psi, just barely in the yellow.

My key point is if a backwash/rinse cycle drops the pressure and restores flow, the sand was clogged and it's not a pump issue, no matter how much pressure rise/drop there was before/after.

I agree. Pump seems to work fine with a quick backwash or sand filter in recirculate mode - so the pump appears to be doing what it's supposed to. From what little I know about fixed speed impeller pumps, I don't know what else could cause it to slowly 'slow down'. Makes more sense that it's the sand filter getting fouled up.

Already thinking about investing in the next size up sand filter/pump for next season - want to learn what I can this season!

 

[jseyfert3]

I think mknauss was implying that whatever may be off with the water chemistry is producing particulates that are fouling the sand filter quickly.

Yes, that's not mutually exclusive. I think what he was getting at is cloudy water is often a chemistry problem (things are growing) rather than dirt. For example, on my hot tub if I failed to add chlorine for a while before I had a SWCG the water would inevitably go cloudy.

 

[CT-Steven]

We have very similar systems and I did have a flow issue when in filter mode and it went away on recirculate. Part of the problem was I had a little too much sand (was at max height). I removed the sand to where it is between the min/max line (on the lower side) and things got better. Also I removed the screw on the (2) intakes as I found the grates inside were catching debris and now I unscrew them to clean. Also the leaf filter on the input side tends to catch a bit, so look to clean that as well. I backwash once a week and ever second week I disassemble the filter and deep clean the sand. Its more maintenance than I wanted but it has become a routine and I can now do it in about 15 minutes.

I will be upgrading the intakes to the 1.5" variants along with their hoses and the largest pump they make for next season. They are barely adequate for the size pool as everyone notes. I'll also probably cut in a skimmer which will dramatically help with top level debris and the need to vacuum almost daily.

 

[PieterS]

I backwash once a week and ever second week I disassemble the filter and deep clean the sand. Its more maintenance than I wanted but it has become a routine and I can now do it in about 15 minutes.

I will be upgrading the intakes to the 1.5" variants along with their hoses and the largest pump they make for next season. They are barely adequate for the size pool as everyone notes. I'll also probably cut in a skimmer which will dramatically help with top level debris and the need to vacuum almost daily.

Looks like you also have a saltwater system similar to mine. Every time you backwash or clean the filter - are you re-setting the synchronization between the two systems? Since the pump must be on of the SWCG to work, it's a PITA to 'break' that cycle every time I backwash or want to vacuum the pool - unless there's a way around that.