Pressure gauge

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azanclay

azanclay

Well-known member
May 27, 2020
51
Atlanta, GA
Pool Size
32000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I bought the fancy pressure gauge from tftestkits.net. My filter was just replaced yesterday and i told the pool guys to install my fancy gauge on the filter.

Yesterday, the baseline pressure was 7.5. I’ve backwashed twice between 1pm yesterday and 8 am today. After I backwashed today the baseline pressure was 11 psi. I checked back every 30 minutes it dropped so now it is about 10 psi. What can be causing the baseline pressure to increase in a new filter from 7.5 to 11? I’ll check again to see if the psi keeps dropping. But yesterday it was increasing 1 psi every hour.

I did notice this morning there was a leak at the drain, I already tightened it and no more leak. Could that be a reason why the pressure was lower yesterday?
 
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Remember that the gauges from tftestkits are glycerin filled and generally provide a more accurate/reliable reading. Now that you have a new filter, the readings can vary slightly. That said, an increase in pressure generally means that the filter is getting dirtier quicker. Sometimes it is easily explained from dirt or vacuuming, while other times it may the onset of algae. What is your chemistry like? If you post a full set of test results it might help in evaluating your situation.

As to the drop in pressure, perhaps some was lost due to the loose drain. A bit hard to tell at this point.
 
Here are my test results-

cya 40
FC 18
TA 70
Hardness 70 ( vinyl pool)
Salt 1800 ppm (haven’t added any salt yet. This is whatever remaining from last season).
pH was 7.2 before started slam
 
Here are how the pool look like today6DDAA764-51E1-4C01-A71A-4B8BDAAA8B42.jpeg
 

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A,

Glycerin filled gauges have a little plug or stopper that you need to pull out and then put back in. This adjusts them to the air pressure.

Did you do that?

That said, I suspect that you have algae. (Edit.. I see that you are SLAMing, in which case you should see a quick increase in the pressure.)

Thanks,

Jim R.
 
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The drop in pressure could've just been something odd. A change in pump speed, settling of the new sand, or something else. Normally I wouldn't anticipate to see a drop in psi unless it was due to a drop in pump speed or after a backwash. Not as common, but the psi might also drop temporarily of the system was struggling to get water. An example would be a partial blockage or the skimmer weir door being partially closed.
 
Texas Splash said:
The drop in pressure could've just been something odd. A change in pump speed, settling of the new sand, or something else. Normally I wouldn't anticipate to see a drop in psi unless it was due to a drop in pump speed or after a backwash. Not as common, but the psi might also drop temporarily of the system was struggling to get water. An example would be a partial blockage or the skimmer weir door being partially closed.
Click to expand...
Ok that makes sense. I was/am using skimmer sock and the water at the deep end was almost at the top of the skimmer door yesterday. The water level is lower today after backwashed.
 
Jimrahbe said:
A,

Glycerin filled gauges have a little plug or stopper that you need to pull out and then put back in. This adjusts them to the air pressure.

Did you do that?

That said, I suspect that you have algae. (Edit.. I see that you are SLAMing, in which case you should see a quick increase in the pressure.)

Thanks,

Jim R.
Click to expand...
Yes I did. It did release a little bit of oil but I quickly pushed the plug back in.
 

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The little psi drop was probably due to the leak. Algae will definitely increase psi.
Example: I just opened my pool (clean & clear no algae), my normal psi is around 10.5-11psi, my gauge was reading 10 & sometimes less. Turns out my pump basket oring was leaking. Fixed that & the psi returned to normal. Since you also introduced air into the system to change the filter out it can take little time for things to even out & fully get all the air out. This is especially true with a really large sand filter.
As mentioned your new filter’s clean psi may differ from your old filter’s clean psi. Now that you’ve fixed the leaks, note your clean pressure after backwashing & then when psi increases 25% over that it’s time to backwash.
 
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I
Mdragger88 said:
The little psi drop was probably due to the leak. Algae will definitely increase psi.
Example: I just opened my pool (clean & clear no algae), my normal psi is around 10.5-11psi, my gauge was reading 10 & sometimes less. Turns out my pump basket oring was leaking. Fixed that & the psi returned to normal. Since you also introduced air into the system to change the filter out it can take little time for things to even out & fully get all the air out. This is especially true with a really large sand filter.
As mentioned your new filter’s clean psi may differ from your old filter’s clean psi. Now that you’ve fixed the leaks, note your clean pressure after backwashing & then when psi increases 25% over that it’s time to backwash.
Click to expand...
Thanks. The pressure is now back to 7.5 psi (which was the baseline pressure yesterday) . I clean my pump filter basket every morning during this time of year (I hate to see the tassels blocking the flow to the pump) and I dont see any air bubbles in the pump basket so I don’t think I have a leak. Return lines have strong pressure and water is clearer today than it was yesterday. I think I’ll wait it out and see what happens .

Could the pressure gauge be faulty? I used this gage in the old filter for a few weeks. When I noticed the old filter had a crack and leaked, it leaked from the tank shell and also water was gushing out where the filter gauge was. This was the same gauge i used. I did not check what the psi was but I am pretty sure it was at the max.
 
Because the pressure goes up and down. 11 psi after backwash this morning. (Yesterday it was 7-7.5 psi after backwashed twice). Then the psi dropped from 11 to 7.5 about a few hours ago. Went up to 8 psi. Then now dropped back down to 7 psi. I’m afraid I’m overthinking this or overwatching my gauge :LOL:
 
A,

I assume your old gauge was a 0 to 60 gauge, while your new one is 0 to 30. So smaller changes look larger.

I don't see a problem.

What kind of pump and filter do you have?

Thanks,

Jim R.
 
Jimrahbe said:
A,

I assume your old gauge was a 0 to 60 gauge, while your new one is 0 to 30. So smaller changes look larger.

I don't see a problem.

What kind of pump and filter do you have?

Thanks,

Jim R.
Click to expand...
Yeah that is true. New gage is 0-30 and old one was a cheapie 0-60. Pentair single speed 1.5 hp pump and hayward sand filter pro series s244T. What is the reason for backwashing when pressure increases by 25%? I read elsewhere to do it when the pressure increases by 8-10 psi above baseline
 
The idea behind the recommendation is that you backwash when the filter needs it instead of on a schedule or some arbitrary psi # that doesn’t make sense for your pool. Sand filters actually work better when they are a little bit dirty.
 
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