Backwashing doesn't seem to lower pressure

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D

DJ13

0
Aug 21, 2014
28
Ottawa, Ontario
I've posted about my cloudy pool before here and was able to clear it up by slamming and it didn't go clear until I regularly backwashed.

The same thing is happening again and again I have what I think is near-perfect water, see below for numbers. This time though when backwashing the pressure does not seem get any lower. I usually have the pump set to about 3000 RPM for a couple hours to skim the top debris and then lower it to ~2500 to continue to filter the water. Once I noticed the water getting cloudy again I boosted the RPMs up to max (3450) and saw that the pressure climbed to about 25. Backwashing did not seem to bring it down much, maybe I didn't run it long enough but the water seemed to run clear after a couple minutes.

I know I should probably do a deep clean but the filter (Jacuzzi Laser 250) has a very small opening and it is in an enclosed shed so I can't overflow it and don't think I can get my sump pump and garden hose into the filter. Are there any other options to try to see if this is purely a filtration issue?

Test results:
FC: 3-5 ppm (currently holding it a little higher)
CC: 0
pH: 7.6
TA: 90
CH:110
CYA: 25
 
Welcome!

I haven't done it yet, but I have my filter in a finished Pole barn/poolhouse with furniture, etc so I've been pondering the same thing. When I drain it for winter, I've now rigged up a "system" where using clear hosing you can buy by the foot at Home Depot/lowes then connect it into the shop vac hose and secure with duct tape. That works for draining, but not for cleaning, where the point is to overflow the top.

This year we're going to disconnect it and dolly it outside to clean the sand.

I think that would probably be your best option as well.

With that said re:cloudiness, how many hours a day are you filtering? And when you backwash, how any minutes are you doing it for? Do you use rinse cycle to re-settle the bed?

Lastly, does your FC ever drop below 3 by the time you dose again? If so, maybe kick your target up just a bit.
 
kimkats said:
That is the bad thing about having the equipment in an enclosed area.

You need to find a way to get inside the filter and clean it out. There is something going on.

Have you done an OCLT? Here is a link on it. I wonder if you have something brewing?

Pool School - Perform the Overnight FC Loss Test (OCLT)

Please try to do this test tonight a let us know what it finds.

Kim
Click to expand...


I did this last night and there was 0 loss overnight, 3.5ppm at night and this morning before the sun hit the pool. The water is still cloudy and the dirt settles to the bottom. I backwashed again this morning (always with rinse at the end) but did not see any drop in pressure; it stayed at 24 PSI @3000 RPM. There may also be a small leak at the collar and I'm worried that with such high pressure it may fail completely. I will try to remove the multiport tonight or tomorrow and try swampwoman's suggestion of at least using a shop vac to remove the water so I can at least try to get a garden hose in there to stir up the sand.

To answer the other questions I have a VS pump that runs overnight for about 10 hours at various speeds. For the backwash I usually leave it for 2-3 minutes since the water does appear to run clear and then run the rinse for about 30 seconds.

Are chemical filter cleaners an option? I know Filter Perfect has been recommended to be from a pool store but I realize the best option is opening it up and deep cleaning.

My plan would be to:
disconnect the plumbing to the multiport
remove multiport
use shop vac to drain water off the top of the sand
garden hose into filter sand
repeat steps 3 and 4 as needed

20150818_082602.jpg
 
I'm not sure why the article doesn't mention it, but they usually recommend you do the OCLT with a higher FC level, like 10 or so.

I don't think you need to shop vac out the water, just stick the hose in and carefully stir up the sand.
 
The shop vac method seems to work, I was able to do a couple of cycles of cleaning by taking the water off the top and then using the garden hose without overflowing but will have to wait for the weekend to really do a full clean.

What is the likelihood that the dirt in my pool is actually sand from the filter? I have set the port to bypass the filter so I can at least still circulate the water and keep FC up. I don't think this would be the case though since I was able to clear up the pool last time by multiple backwashes.
 
What is the likelihood that the dirt in my pool is actually sand from the filter?
Click to expand...

Can you post a pic of your water?

I thnk we have to make a distinction between dirt and cloudiness. Eg. In my (clear) pool I get dirt blown in any time there's wind, and a bit of sand from the filter sometimes at the far end of the steps, but never cloudiness.

Every situation is different but I usually suspect mechancal filter issues (as opposed to under-filtering) last in terms of cloudiness ;)

But this might be because I recovered a foreclosure swamp on the same sand filter, same sand, without any tinkering, without even cleaning it... and it still polishes my water just fine ;) Sand filters ergo seem a bit indestructible to me ;)

With cloudiness, the normal culprits are:

A) nascent algae...which will raise filter pressure...(but usually most likely when someone has high cya, which you don't)
B) chem reaction...eg. High calcium (but yours is normal) or adding Metal Sequestrant, which can sometimes cloud up fir a few days and raise pressure.
C) Not filtering long enough in the thick of summer

In your case, had you just posted that the water was cloudy but you passed the OCLT, I would have suspected that you simply needed to be running the filter LONGER at normal, not low for a few days and maintained your FC a little higher to be on the safe side. (You might want to rerun the OCLT at 10 ppm FC to truly test for organics)

But since you reported evidence that frequent backwashing cleared in the past...it made the filter seem more likely to be the issue ;)

So, with the water only running on recirculate, has your water cleared? If not, I don't think the filter is CAUSING the problem per se, though it might be exacerbating it.

I know TFP and Taylor kits are hard to get in Canada...what are you testing your CYA with? You've been following TFP for a while now right?

If so, and you're really confident your FC never drops below the min. in the cya:chlorine chart (click on link in my signature) then I'd be inclined to see what happens if you ran your filter for a day or two straight, and did a longer backwash, eg. good 5 min. followed by a min. on rinse and see if it clears.

If something in your environment is blowing in a fine dust that the fiter isn't catching, you can also try a bit of DE in the filter for finer capture, or once your REALLY confident nothing else is going on and that particles are getting past the filter, clarifier (which we don't normally recommend unless its clear te more likely culprits such as ascent algae aren't at work.)

A second test might be to hold a piece of cloth or paper towels in front of a return to see is any dirt/particulate is blowing FROM the filter once you're back in filter mode. That might help dx at least the filter's function ;)
 
Hi again. I just quickly checked your other posts and saw this pool is new-to-you this year ;)

Just want to cover a few quick things to make sure you've encountered this info before:

1. Only backwash when pressure rises 25% above normal...what's normal for your filter?
2. Have you ever cleaned out the pump basket? Goid to do now and then for normal pump operating if like me you get pine needles and other stuff clogging it.
3. You didn't change the sand or anything when you moved in, did you? (Generally don't need to, but just checking as there's been a few cases where people have used the wrong grade of sand in the filter and had cloudy issues. In one case, a bag was actually mislabeled for pool but wasn't 20 grade silica.)
 
Yes, this is my first full season with the pool. We have upgraded the pump and heater and was thinking we may have to do the filter as well since I have no idea how much maintenance was done. It seemed like they took pretty good care of everything but it is not a new pool by any means. I have not changed anything to do with the filter.

I tried to get samples of the dirt but could not seem to pull any up in a meaningful amount. Personally I think it is more of a dirt than "cloudiness" but my lack of experience is why I'm here. From reading here cloudiness seems to imply more of a chemical problem (which I'm definitely not ruling out) but it seems to settle to the bottom each night. My plan for the weekend is to finish the deep clean on the filter and see how the pressure changes and run it constantly with lots of brushing to try to clear it.

To address some of the other questions, it seemed that a normal pressure was around 18 for the old pump (single speed) and it was a little higher with the new one, maybe low twenties. Right now at near max RPM the dial reads 28. I do check the pump filter regularly and most of the debris seems to get captured at the skimmer basket.

Here are a couple pictures, the first is a picture of the shallow end where I made a sweep with the brush, you can see the much lighter blue streak where the dirt was disturbed. There is a brown plume that gets kicked up when I brush. The second is of the stairs, I couldn't get a better picture, just my phone for now, can take better pictures on the weekend.

20150821_083927.jpg 20150821_083456.jpg
 

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Good morning.
I know you're planning on filter-cleaning this weekend, so hopefully things will be a big more clear, metaphorically and literally ;) Tell us how the sand looks when you do it.

Hard to tell from pix but in your shoes I'd take the FC up to 10 after dark and do the OCLT tonight, reading the result before dawn.

I've also seen pollen look like that, but that's normally in spring.

If you hold a piece of white cloth (eg a wite tshirt or paint rag) right over the return for a few minutes and then immediately pull it up, see if whatever its captured (if anything) will smear OR is gritty. If it smears, its organic and if its gritty, eg sand like, then I'm more suspicious of the filter.
 
Swampwoman said:
Good morning.
I know you're planning on filter-cleaning this weekend, so hopefully things will be a big more clear, metaphorically and literally ;) Tell us how the sand looks when you do it.

Hard to tell from pix but in your shoes I'd take the FC up to 10 after dark and do the OCLT tonight, reading the result before dawn.

I've also seen pollen look like that, but that's normally in spring.

If you hold a piece of white cloth (eg a wite tshirt or paint rag) right over the return for a few minutes and then immediately pull it up, see if whatever its captured (if anything) will smear OR is gritty. If it smears, its organic and if its gritty, eg sand like, then I'm more suspicious of the filter.
Click to expand...

After cleaning the filter I am now thinking it is an algae bloom despite my never seeing any CC in my tests. I put a white dishtowel in front of the return and did not notice anything being caught. The deep clean did clean out some cloudy water but it wasn't filled with crud like a lot of stories I've read here and the pressure did not go down at all. I've brought the FC up to SLAM level and am brushing twice a day.

Are the DPD tests a valid alternative to the powder in the K-2006 kit? Specifically the R-0001 to R-0003 reagents. I can't find a refill in Canada for any kind of reasonable price (the R-0870 is $35 and R-0871 is $53).

I'll do the overnight test tonight at shock level with my dwindling supply of R-0871.
 
Dj13, I could be wrong, but I don't think the other solutions can stand in for R0817 unfortunately, and I do know they're expensive in Canada. Perhaps ChemGeek will come along -- he is most likely to know if there is a less expensive alternative to R081 in Canada...

In the mean time, after the OCLT, you could try to stretch things out a bit by testing 5 mil instead of 10 I suppose. And while we don't recommend it, i have seen folks use dilution with the oto test kits in an effort to slam correctly when desperate ;)

In a pinch, you could also slam with r0817 alone and just do the OCLT for 2 or 3 nights in a row -- eg extend the lam to perfect clarity and no overnight loss...that would save you $35 but of course would be fc set by extra chlorine cost.
 
The only thing you can do is carefully dilute with distilled water and use a DPD chlorine test. However, the error is so large in that test that you will miss more subtle chlorine losses, but at least you should be able to see larger ones.

The FAS-DPD really is a great chlorine test because it lets you measure high chlorine levels during a SLAM and gives you good accuracy for an OCLT. Unfortunately, the exclusive Taylor distribution in Canada has Taylor products, and especially the FAS-DPD test, be expensive.
 
I added a bit (like 1/4 cup) of DE to my sand filter and that was amazing in clearing up my cloudy water after a SLAM of a green pool....it's now perfectly clear. I'm a newbie, but figured I'd mention that it helped my sand filter clear all that up.
 
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