How to release air from sand filter

[BullishBear]

My sand filter (model details in signature) does not have an air relief valve. Don’t Sand filter need an air relief valve? Any suggestions on adding one either by adding an adaptor (with relief valve in between filter and pressure gauge) or installing a pressure gauge with in-built relief valve?

Context: Although my filter’s pressure hasn’t increased more than 5 psi from the normal level (21 psi after last backwash), it has been 5 months since I backwashed. I thought I should only do it after >= 5-10 psi from normal but learnt that I should do it every few weeks especially after lot of leaves fall during fall and early spring. I will be backwashing tomorrow. My neighbor, having DE filter, also mentioned to frequently relieve air from filter to help better but I don’t have one.

 

[Texas Splash]

Don’t Sand filter need an air relief valve?

Not all. Some do not and excess air is passed through the lines.

my filter’s pressure hasn’t increased more than 5 psi from the normal level (21 psi after last backwash), it has been 5 months since I backwashed. I thought I should only do it after >= 5-10 psi from normal

Here at TFP we recommend a backwash when the filter pressure increases by about 25%. You mentioned a current psi of about 21 which seems a bit excessive to me. I would do a good backwash then record your psi. If it doesn't drop significantly you may have a problem with the gauge.

 

[BullishBear]

@Texas Splash Thank you for the response!

Not all. Some do not and excess air is passed through the lines.

Will this not increase suction side air leaks and thus to more water loss? Either ways, is it recommended to replace the existing gauge with one that also has air relief valve? Just want to make sure I don’t regressively impact the filter.

 

[BullishBear]

Here at TFP we recommend a backwash when the filter pressure increases by about 25%.

Can you please clarify whether it is 25% of the benchmark level that shows right after backwash or 25 psi?

 

[Texas Splash]

Can you please clarify whether it is 25% of the benchmark level that shows right after backwash or 25 psi?

Sure. You can see that discussion on this page.

Routine Pump/Filter Maintenance

A working Filter and pump are vital parts for your pool. Read our artiticle on how to clean your filter & other Pool Maintenance Tips.

www.troublefreepool.com

 

[BullishBear]

@Texas Splash Regarding your comment on 21 psi to be excessive, my backyard is very big. Following are the recorded distances of structures from filter/pump: Spa & Skimmer-1 are 80 ft away. Main drain & Skimmer-2 are 110 ft away.

Given this context, do you still think the nominal pressure post backwash should be lesser than 20 psi or this longer distance may contribute to higher nominal psi? I read 10 psi in many articles, is that correct? Btw the guage goes to 0 psi once pump shuts down.

 

[BullishBear]

@Texas Splash Thanks for sharing the article. I read and it answered the questions on when to backwash (> 25% of benchmark) and nominal pressure range, which I understood as —> longer plumbing leads to lower benchmark pressure (not higher) and subsequent slow raising of pressure over time. I will give a good backwash today and record the baseline.

One last question stands, is it advisable to replace the existing gauge with one having air relieve valve? Is it worth it and will it be OK for sand filters?

 

[Texas Splash]

is it advisable to replace the existing gauge with one having air relieve valve? Is it worth it and will it be OK for sand filters?

I personally wouldn't worry about it. It's not really necessary as air trapped inside is naturally pushed out through the returns on flites without the air relief.

But if you really want to pursue looking into a way to add one, some people have used one like the item linked below.

https://www.amazon.com/Hayward-DEX2400S-Filter-Adapter-Assembly/dp/B0032UXRJG

 

[BullishBear]

I did a thorough backwash (2 mins of backwash + 30 seconds of Rinse). But the pressure readings went through a rollercoaster thereafter.

Before backwash: 26 psi
During backwash: 14 psi (lowest)
After backwash: 20 psi

I did a thorough scrubbing of the wall and pool bottom. Probably I did this after two months and so.

After brushing: 28 psi !!

Looks like I fooled myself. I should have first brushed my pool before backwashing!

Should I backwash again? Is it normal for pressure to fluctuate this much after scrubbing the pool? Will there be any other problems with filter or gauge?

Thanks!

 

[BullishBear]

A week back, last Monday, I did a thorough backwash (2 mins of backwash + 30 seconds of Rinse). Following are the pressure readings throughout this process.

Before backwash: 26 psi
During backwash: 14 psi (lowest)
After backwash/rinse: 20 psi
<I did a thorough scrubbing of the wall and pool bottom. I haven't done it for a long time and so there were lots of visible dust/dirt came off from the walls.>
After brushing: 28 psi !!
<A lesson for future, I should have first brushed my pool before backwashing!>
After a week, yesterday: 21 psi
After brushing, today: 22 psi

Question:
1. Is it normal for pressure in Sand filter to have this much variance?
2. Is it possible for pressure to subsidize after spiking earlier i.e. during scrubbing the pool vs after a week?
3. Is this an indication of any existing issues with the filter or the pressure guage?

 

[Texas Splash]

It makes sense your filter pressure will fluctuate during the various MPV settings. There's different resistance in the system in those settings. Your biggest pressure focus should be on the clean (just backwashed) psi and then later as it climbs to show it's dirty (25% higher). That's when you backwash.

A thorough brushing could potentially releasing organics you would not otherwise see with the naked eye.

A gauge can always go bad, but if it's falling to zero when the system is OFF, that's good. PSIs vary from pool to pool and the rpm settings at the time of reading. For a good reference, pick an rpm that provides adequate resistance to the filter gauge, record that starting (clean) point, and watch to see when it climbs. When it increases by 25% it's time to backwash. If you find extreme pressures or variances over a short period of time, it may be worth doing a sand deep cleaning if it hasn't been done in a few seasons.

If the PSI increases quickly after backwash, consider doing an Overnight Chlorine Loss Test to ensure excessive organics/algae isn't the cause. Hope that helps,

 

[Newdude]

If the PSI increases quickly after backwash, consider doing an Overnight Chlorine Loss Test to ensure excessive organics/algae isn't the cause. Hope that helps,

+1. So many people want a chemistry issue to be a mechanical issue, when on the contrary, the filter is working GREAT and clogging with exponential growth algae.

If you pass the OCLT, then you know it's one of the rare time it was a filter issue.

 

[BullishBear]

Thanks. OCLT passed, there was only a loss of only 0.5 ppm overnight. My pump is single speed and just backwashed PSI is 21. I will take this as a baseline and backwash in future when it crosses 26 PSI (125% of baseline).
@Texas Splash @Newdude My only outstanding question is, can the pressure read higher just after thorough brushing and subsequently in 2-3 days goes down by 3-4 PSIs which happened in my case? If those organics released during brushing stays in the filter how the pressure comes down in few days?

 

[Texas Splash]

My only outstanding question is, can the pressure read higher just after thorough brushing and subsequently in 2-3 days goes down by 3-4 PSIs which happened in my case? If those organics released during brushing stays in the filter how the pressure comes down in few days?

That does seem a bit odd. Not really sure. First we would have to assume there is enough stuff being released into the water just from one brushing which on its own would seem odd. And if it happened that way, then it would later resolve itself with a lower pressure? Now that you have a good starting baseline to start with, maybe watch to see if you observe any other times when the pressure does the same thing. I wonder if it's just a normal fluctuation your gauge picks-up every once in a while.

 

[Newdude]

My only outstanding question is, can the pressure read higher just after thorough brushing and subsequently in 2-3 days goes down by 3-4 PSIs

Weird because 'just after' brushing, 99.999% of the pool water isn't going through the filter and will take quite some time to find it's way there.

Have you deep cleaned the filter ? There's no telling the last time the old owners did, or what kind of magic potions gummed up the sand.

 

[BullishBear]

@Texas Splash @Newdude Thanks for the response.

I mean, just after brushing, meaning a good 30 mins of brushing all walls and floor. I push the bottom floor’s sediments (there are sand like sediments in bottom - no pool cleaner used) towards main drain. And then probably 5 mins after brushing, I go and check the filter pressure. Sorry for the miscommunication.

No I have not deep cleaned myself since owning this property in last 7 months and I don’t know when it was last done by previous owners! After reading Sand Filter care article and watching Deep Cleaning videos shared, I too think it’s time to do it. I will be ordering the o rings and spider gasket. I will try deep cleaning once I have them on hand.

 

[Newdude]

meaning a good 30 mins of brushing all walls and floor.

That still doesn't leave alot of time for what you've brushed up to get to the filter. Yes you're brushing it towards the drains but the bulk of it gets suspended in the water and needs hours and hours to get filtered.

, I too think it’s time to do it

Yeah. No telling if it was ever done, or what has been put through the filter since it was done. You'll either find filthy sand, which will clean as good as new, or gummed up clumps of sand which can't be saved. You'll know as soon as your hand gets in there.

Going forward you'll have a good baseline for performance and pressure. And you'll be able to state exactly what products may be found in the filter, none of which will harm its capabilities.

 

[BullishBear]

@Newdude @Texas Splash I successfully deep cleaned my filter also took apart and lubricated the MPV parts as I had to fix this: Sand Filter MPV Leaking. Post deep clean, 30 secs of backwash/rinse, the filter clocked 20 psi on Filter mode. I recorded it in Poolmath and will backwash next when crossing 25 psi! I also found the gauge replacement is pretty straight forward. Ending the weekend with satisfied DIY experience! Thanks.