High PSI with new sand

dizuane

New member
Jun 18, 2020
3
Virginia
I'm experiencing extremely high PSI in my sand filter (Sand Dollar SD60). I'll backwash and within an hour or so it's at 23-25psi and the jets are pushing little to no water out in the pool.

I've replaced the sand, cleared the water of algae, cleaned the sand after clearing the water with a chemical cleaner, replaced the multi-port valve and plumbing.

My first thought was air getting in - but when it is recirculating, the PSI stays at a constant 10psi... so I don't think it's the valve or plumbing.

Could it be the pipe or laterals inside of the filter (as far as I can tell, no sand is getting in the pool)? There was a small amount of sand in the drain plug, but I haven't seen evidence of sand anywhere else that I can tell. The water is cloudy but the chlorine is high from the intense shock to clear algae.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
30,934
Laughlin, NV
Welcome to the forum!
The situation you describe is due to algae in your water. A single 'shock' does not clear a pool of algae.
You need to follow the SLAM Process. To do that, you need a proper test kit, see Test Kits Compared. I suggest the TF-100 A proper test kit is needed to get the accurate water chemistry results needed to follow the TFP protocols.

While you are waiting on your test kit, add 5 ppm FC worth of liquid chlorine / plain bleach to your pool each evening with the pump running. This will replenish the FC lost each day to the sun and also inhibit any algae in the water from growing further.
I suggest you read ABC's of Pool Water Chemistry.
 

splashpad

Bronze Supporter
Aug 2, 2017
2,708
SE Kansas!
Welcome to TFP!
I'm experiencing extremely high PSI in my sand filter (Sand Dollar SD60). I'll backwash and within an hour or so it's at 23-25psi and the jets are pushing little to no water out in the pool.

I've replaced the sand, cleared the water of algae, cleaned the sand after clearing the water with a chemical cleaner, replaced the multi-port valve and plumbing.

My first thought was air getting in - but when it is recirculating, the PSI stays at a constant 10psi... so I don't think it's the valve or plumbing.

Could it be the pipe or laterals inside of the filter (as far as I can tell, no sand is getting in the pool)? There was a small amount of sand in the drain plug, but I haven't seen evidence of sand anywhere else that I can tell. The water is cloudy but the chlorine is high from the intense shock to clear algae.
Do you have a good test kit for water levels? Test Kits Compared - Trouble Free Pool
List of Recommended Pool Chemicals - Trouble Free Pool

And to answer your question, your filter is collecting the algae that is being killed off. In order to clear your pool fully, we recommend the SLAM Process which requires you to be able to monitor your chlorine levels accurately (using one of the test kits linked above).
 

dizuane

New member
Jun 18, 2020
3
Virginia
I do use a home test kit.. Taylor brand, K1005 I believe.

My chemicals are definitely off. I had a local store test it yesterday:
- Free/Available Chlorine 20ppm (from intense shock to clear the algae)
- pH 8.5 - Added liquid muratic acid yesterday
- Alkalinity - 65ppm (adding increaser today)
- Calcium - 200ppm (adding calcium tomorrow)

Are you suggesting that the PSI is running this high due to the chemicals being off balance? With the jets not producing very much water, and the PSI being that high, should I not be concerned about continuously running the filter? Note, the pool is clear of algae now.. last shock was night before last.
 

tim5055

Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
10,976
Franklin, NC
I would not raise the TA above where it is. Higher TA will just cause your pH to rise faster.

Yes, your pressure is going up because the filter is doing what it's designed to do, filter out the dead algae. As it filters it plugs up and the pressure goes up.

Marty has already said a couple of "shocks" won't eradicate the algae. It just knocks it back.

How much Pool School have you read? Start with these:






 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
23,866
San Dimas, CA (LA County)
The money you just wasted on alkalinity increaser and Calcium would have been better spent on a proper test kit. I don't even want to think about what you spent on sand and plumbing. You've been pool-stored.

65 is fine for TA. And if you needed more, the grocery store could sell you the exact same chemical for about 80% less.
Your vinyl-lined pool has no plaster to damage with low CH. 200 is more than enough to keep the water from foaming.

Your problem is algae. My guess, based on probability after reading hundreds of similar threads, is that you've been chlorinating with pucks and doing the weekly "shock" and you have so much CYA built up that even 20 FC is insufficient to kill the algae. And if I'm right, you'll need to replace a bunch of water and it makes no sense to put a bunch of chemicals in the water only to pump it out a day or two later.

Your pool may not be green. But I'm betting it's cloudy. And it will be green again if something doesn't change. My advice to you is this: order a proper test kit. That's a Taylor K2006C. The C is critical. Or a TF!00 with the XL option. Then read the links the others have pasted. If that gets too confusing, scroll through and look at the pictures. The newer ones are last. Do what they did.
 

dizuane

New member
Jun 18, 2020
3
Virginia
Thank you all for the links.. I'll definitely do some research, get a test kit and start the SLAM process.

I just want to triple check this pressure thing, though, and rule out any issues with the filter. So I understand it's normal for the psi to be high due to algae - but - shouldn't backwashing/rinsing as well as the cleaner I used last night lower that psi? After cleaning and backwashing, the psi is up back up to 25 within within 30min or so and the jets are barely pushing anything back in. At what point should that psi start to stay lower?
 

splashpad

Bronze Supporter
Aug 2, 2017
2,708
SE Kansas!
Thank you all for the links.. I'll definitely do some research, get a test kit and start the SLAM process.

I just want to triple check this pressure thing, though, and rule out any issues with the filter. So I understand it's normal for the psi to be high due to algae - but - shouldn't backwashing/rinsing as well as the cleaner I used last night lower that psi? After cleaning and backwashing, the psi is up back up to 25 within within 30min or so and the jets are barely pushing anything back in. At what point should that psi start to stay lower?
You should backwash the sand filter as soon as it's 25% over clean, letting the pressure get any higher just forces the filtered particles deeper in to the sand.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
30,934
Laughlin, NV
As you say, after backwashing the pressure is back to normal. Then as you pump algae filled water through it, it plugs up.

Until you address the chemistry issue and eradicate the algae, your filter will plug up.
For now, you are best to put the MPV on Recirculate, run the pump enough to mix in the liquid chlorine I recommended above, and then turn the pump off for the day.
 
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tim5055

Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
10,976
Franklin, NC
Thank you all for the links.. I'll definitely do some research, get a test kit and start the SLAM process.

I just want to triple check this pressure thing, though, and rule out any issues with the filter. So I understand it's normal for the psi to be high due to algae - but - shouldn't backwashing/rinsing as well as the cleaner I used last night lower that psi? After cleaning and backwashing, the psi is up back up to 25 within within 30min or so and the jets are barely pushing anything back in. At what point should that psi start to stay lower?
The PSI will start to remain lower when you eliminate the algae.

What "cleaner" did you use? Many things that sound great to use actually gum up and clog the sand of sand filters.

The only thing you should be using right now is liquid chlorine and acid to keep the pH in check.