High pressure in sand filter

[Stefany]

Hi All,

First, please excuse my poor language. French woman in USA need to learn a lot to improve her knowledge.

And about knowledge, let's explain my problem :

My pool system, built 5 years ago, has never been in trouble. A month ago, I noticed the filtration PSI (before at 13) moves to 25, without any modifications. I used to clean filter at 15 and backwash did nothing. To try to solve the problem, I bought new gauge, then new sand ,then new multiport valve. Nothing happens, same high pressure without any explanations.

PSI are : filtration (25) backwash (12) rince (17). Recirculation position and closed position of the multiport valve have a very bad issue : the pressure is so high that multiport valve becomes stucked.



Am I right with the following :

1. They are only 4 possible causes of high psi : filter, inlet pipe, inlet nozzles, multiport valve

2. If in the rince position (so without inlet system) there is still high psi, the inlet pipe and nozzles are not the cause

3. if sand has been changed and the grinds checked, the filter is not the cause

4. And if I have already bought a new multiport valve .... I have no more cause to my problem.

So it means I am wrong somewherere, but where?

Can you help me to find a solution?



Thanks.

 

[Texas Splash]

Bonjour! You have done a lot of work, but the problem may be chemistry. Filter pressure can increase quickly when the chemistry is not correct (algae). Do you test your own water with a TF-100 or Taylor K-2006C test kit? Either one of those kits will work, but you need one of them. That would be step #1. You can test this theory by placing your multiport valve to RECIRCULATE. If the filter pressure gauge goes down, you know the filter is struggling with algae.

Let us know if you have any questions about the test kit or what to do next. The link below is a good place to start as well.

Pool Care Basics Archives

Your one-stop shop for all things TFP to include: ABCs of Water Chemistry, Recommended Chemicals/Levels, Test Kits, Troubleshooting, and much more!

www.troublefreepool.com

 

[SDor]

Recirculation position and closed position of the multiport valve have a very bad issue : the pressure is so high that multiport valve becomes stucked.

If I understand this correctly - that there is high filter pressure when the valve is set to "recirculate" than, to me, this points to a multi-port problem. With my filter, when I set to recirculate, the water bypasses the filter so the pressure of the filter is very low (like 0). If you're seeing a high filter pressure on recirculate, it seems like your multiport valve is connected incorrectly or has something broken inside of it. I don't think you're supposed to run the pump when the multiport is set to "closed".

 

[D.sebens]

Also just to clarify. Don’t change modes with pump running. It sounds like you might be changing them while running from you post stating the handle gets stuck there. That can blow out gaskets or break components from the huge amount of water having to change directions

 

[Stefany]

Bonjour! You have done a lot of work, but the problem may be chemistry. Filter pressure can increase quickly when the chemistry is not correct (algae). Do you test your own water with a TF-100 or Taylor K-2006C test kit? Either one of those kits will work, but you need one of them. That would be step #1. You can test this theory by placing your multiport valve to RECIRCULATE. If the filter pressure gauge goes down, you know the filter is struggling with algae.

Let us know if you have any questions about the test kit or what to do next. The link below is a good place to start as well.

Pool Care Basics Archives

Your one-stop shop for all things TFP to include: ABCs of Water Chemistry, Recommended Chemicals/Levels, Test Kits, Troubleshooting, and much more!

www.troublefreepool.com

Darn, I didn't know chemistry could cause high pressure. I checked the forum, learn many thing with the link you sent to me, and you're right. So now, I know what to do. First buying TF100, Second test my water. I will let you know asap.

About the RECIRCULATE position, when I do it for about 5 minutes and stop the pump, the multiport valve becomes stucked. It's for what I thought the filter wasn' the cause of the problem, because the high pressure is still there in recirculate.

Anyway, i will test the chemistry first and let you know.
Thanks for your reply.

 

[Stefany]

If I understand this correctly - that there is high filter pressure when the valve is set to "recirculate" than, to me, this points to a multi-port problem. With my filter, when I set to recirculate, the water bypasses the filter so the pressure of the filter is very low (like 0). If you're seeing a high filter pressure on recirculate, it seems like your multiport valve is connected incorrectly or has something broken inside of it. I don't think you're supposed to run the pump when the multiport is set to "closed".

Yes, so in RECIRCULATE the pressure is high in the multiport valve. At the filter enter, no problem pressure is "0", but I removed the small valve attached to the multiport valve and replaced it with an other gauge, so I can see the high pressure in RECIRCULATE even the filter has no pressure. So in RECIRCULATE the water doesn't go to the filter but the high pressure is there.
For the "closed" position, yes the pump is closed too. But after a few minutes the multiport valve get stucked and I have to decrease the pressure inside the valve to move it !
Difficult problem to solve.

 

[Stefany]

Also just to clarify. Don’t change modes with pump running. It sounds like you might be changing them while running from you post stating the handle gets stuck there. That can blow out gaskets or break components from the huge amount of water having to change directions

Yes, thanks, I'm alright with that, never moved the multiport valve while pump is running. But when I stop the pump, choose the RECIRCULATE, open the pump and let it work for a few minutes, close the pump and try to change position, I cannot. Have to lower pressure inside the multiport valve to move it !

 

[Texas Splash]

Can you post a picture of your multiport valve and the entire equipment pad please? You said earlier the valve is new, but based on a few things thins you described, I'm beginning to think maybe your multiport valve is bad or perhaps something wrong with the installation. Pictures may help.

 

[Stefany]

Can you post a picture of your multiport valve and the entire equipment pad please? You said earlier the valve is new, but based on a few things thins you described, I'm beginning to think maybe your multiport valve is bad or perhaps something wrong with the installation. Pictures may help.

Hi,
Here the pictures. You can see 3 pipes going down (vaccum, tank and main drain) and on going up (inlet), the multiport valve and filter.
Hope this can help your understanding
Many thanks

 

[Texas Splash]

Thani you for the pictures. I can follow your system water flow fine. I see that you have two pressure gauges yes? One on the multiport valve and one on top of the filter. I think this was confusing to some of us as usually there is only one gauge located on top of the filter not the multiport valve. So for this discussion, we will focus on the filter pressure gauge.

You seem to have a very nice set-up, but it's very possible that your original (rising pressure) problem was still a chemistry issue resulting in the high pressure. Many times excessive organics in the water are not visible to the eye, but cause filter pressure to rise quickly. It can go low after backwash but then go up again. When that happens, the first thing we need to see is a good set of water test results from a TF-100 or Taylor K-2006C test kit. That is very important right now. If you have one of those test kits, please post a full set of results. If you do not have one of those kits, I would highly recommend ordering one. They are easy to use and very reliable. We can assist you with any tests if you have a problem.

 

[Stefany]

Hi,
So it's done with my neighbour's help

FC = 3
PH = 7.2
TA = 60
CH = 120
CYA = 60
CC = 0

When I compares these results with the ABC's of pool water chemistry, it seems to be quite normal.

But, when I read your last post, you said : Many times excessive organics in the water are not visible to the eye, but cause filter pressure to rise quickly. It can go low after backwash but then go up again.

However, when I backwash the pressure doesn't decrease. It's still the same with high level. And i bawash quite every day when I stay close to the filter thinking of the problem and worrying about how to solve it !

I wonder on which area the problem appears if (I don't know) it's not a chemistry problem :

. when I by-pass the filter (MPV in recirculate position) the pressure on the filter gauge (you know now I've got 2 gauges) is high
. when I by-pass the return line (MPV in rince position) the pressure is also high
. the problem is the same when I use any of the succion pipe (vacuum, tant, main drain)

So if it's not the chemistry (not sure, waiting for your experience), not a filter or a return line problem, not even a pipe problem, could the pump causes this?

I start to be anxious about this situation.

 

[Texas Splash]

Very odd. Here are some things that I see:
- High filter gauge pressure (higher than previous history)
- MPV, gauge, and sand all replaced with no improvement
- MVP on recirculate does not effect pressure gauge (this is most odd to me)
- Chemistry? Your FC is low based on your current CYA (see the FC/CYA Levels). FC should be between 7-9 and never below 5 based on that CYA of 60. Normally we expect to see the filter pressure decrease a little after a backwash if you have algae, but there's no doubt your FC is very low and algae may be in the water.

How does the water look? Is it still crystal clear to the bottom? You mentioned doing a backwash everyday, but that's unusual here at TFP. We recommend backwashing when the pressure increases by 25%.

If there was a problem at the pump I would expect low pressure. High pressure is a result of something restricting water flow "after" the pump - usually the filter. So unless you have a valve partially closed after the filter, I still think algae may be an issue.

To be sure, you should do an Overnight Chlorine Loss Test. This will tell us for sure if you have excessive organics or not. If you follow the instructions on that page carefully, it will help us a lot.

 

[Stefany]

Thanks for lot for your time and your help. I will try to come back earlier this evening to do the OCL test (very good instructions) and maybe test again FC/CYA myself
I will let you know
Thanks again

 

[Stefany]

Hello Texas Splash, my only help

I started all over again to make sure I didn't make a mistake (especially I didn't have too much faith in some of the chemical test results that I hadn't done personally).

This is an updates of the problem.

The problem : for several weeks now, I’ve got high pressure in the filter, even after backwash. I could not identify the event that caused this increase maybe it happened slowly. Workers changed a valve which was broken a little before the pump (they changed it in emergency whith water leaking a lot because it was the main drain valve and couldn't stop the flow). The pressure problem came after this intervention, but I cannot say this have caused that. In filtration mode, I had previously about 12 / 13PSI and after backwash the pressure was back to the original level. The water looks clear and well filtered although my impression is that, inside the pool when I touch the pipes, there is a little less suction and a little less return pressure. Before, I backwashed often only after vacuuuming with a pressure 20 to 25 PSI, little in other circumstances because pressure didn’t increased enough in standard process.

I’ve got a pressure gauge on the filter, but I have also installed a pressure gauge on the MPV for checks and analyses. The MPV pressure gauge overcharges a little more than the filter gauge. Here are the results of the measurements according to the origin of the water and the position of the MPV over a complete cycle: filtration, backwash, rinse, filtration. (it's an infinity pool so 3 suction lines : vacuum, tank, main drain).

Pressure data

Water comes from	MPV mode	MPV pressure	Filtre pressure
Vacuum	Filter	22	19
Vacuum	Backwash	15	11
Vacuum	Rinse	16	13
Vacuum	Filter	22	19
Vacuum	Recirculate	18	0
Tank	Filter	21	19
Tank	Backwash	14	11
Tank	Rinse	16	12
Tank	Filter	21	19
Tank	Recirculate	17	0
Main drain	Filter	22	20
Main drain	Backwash	16	13
Main drain	Rinse	18	15
Main drain	Filter	22	20
Main drain	Recirculate	19	0

When the pump is stopped, if I open any valve in filtration or recirculate mode, pressure (MPV and filter pressure) is about 5 PSI (filter pressure is 0 of course in recirculate mode). Admittedly the pump is 7 meters below the pool, but before the problem started few weeks ago, I don't think there was such a high pressure, pump stopped and valves opened. Likewise, since the pressure is high, after a few minutes of operation in the recirculate position, the MPV is blocked and the pressure in the MPV must be lowered in order to move the handle it. Ditto when the MPV is in the closed position. Before, that didn't happen.

Finally, when the problems started, I noticed it because there was a small leak on the MPV and the filter cover (ASTRA99) was lifting up allowing air to escape during the MPV maneuver.

What was done in recent weeks, :

. change pressure gauge

. change the sand and checking all parts of the filter

. install a new MPV : the pressure problem is still there but the MPV no longer leaks

. filter seal replacement :

. filter cover replacement : the pressure problem is still there and the cover is still leaking and even more and more

. lubrication of all joints

. Cleaning pump impeller

. cleaning all pipes with snake and Drain King

. checking air intakes in the suction line and pump

. cleaning SWG (was needed)

. chemistry checks

First conclusions :

. Filter doesn't seem to be the cause : pressure is still high in the recirculate position, when the filter is not working.

. Return line doesn't seem to the the cause : pressure is still high in the rinse mode, when water is filtered the same than in filtration mode except that the water drains to waste water

. Chemistry doesn't seem to be the cause ? (not confirmed because i'm not an expert)


Chemistry :
I did an overnight chlorine loss test (and all the chemistry tests because I was not sure about the first ones I didn’t make by myself).

OCLT :
FC evening = 5
FC following morning = 5

New chemistry results :
FC = 5
PH = 7.2
TA = 60
CH = 120
CYA = 70
CC = 0

Last :
The water looks perfect, crystal clear to the bottom. I don’t do a backwash everyday, but because I'm worried about this problem, I check everyday the system, pump and filter, and turn the MPV trying to understand what happens, many times I move the MPV on backwash to check the pressure and if the pressure would decrease, but unfortunatly, even after « backwash » the pressure is still high.

I think that’s all.

If I’m right, the high pressure is not caused by the filter, nor from any valve on the return line or air in the suction line, nor from the chemistry ?

It's hard to think that we can't find a solution when the problem seems to be circumscribed on a very small perimeter : valves/pump, pump/MPV, MPV/filter, filter/return valve. All this fits on less than 1sqm !

I hope it isn’t hopeless !

And I Thank you for your help.

 

[Texas Splash]

Hello! Well, you certainly have tried to be thorough that's for sure. I'm curious, since the water chemistry seems to be good, and all valves going back to the pool seem to be operating properly, have you considered asking the people who installed your new MPV to come back out and inspect? Maybe open up the filter again and inspect everything inside? While I didn't see anything odd from the pics above, perhaps something is wrong with the previous maintenance? I'm not worried about the psi from the gauge on that MPV because we don't typically use that feature, but the the psi on the filter housing is the one that we refer to. I'm especially concerned that there seems to be enough pressure to lift the filter cover. That would indicate a serious water restriction problem inside or past the filter. If the MPV was bad or installed incorrectly, you would see things like the handle not doing to proper job, or a leak to backwash/waste, but not high filter pressure. With good water chemistry (clear water and passed the overnight test), there has to be a blockage in teh filter or past it.

 

[mariane]

Just a note:
With CYA at 70, your target FC should be in the 8-10 range. at 60, 7-9 range.

 

[Texas Splash]

Stefany, just a reminder, I notice you have a salt pool (SWG) so please add that to your signature along with your test kit and all of your pool details. It would sure help us as we review each post.

I have re-read your last post with all the info. If I focus on the "Pressure Data" chart above and focus on the tank (related to endless feature I'm assuming) and main drain pressures, those pressures are consistent. You mentioned earlier you thought maybe the pressure changes started after replacing the valve before the pump since it was leaking. That leaking valve would've results in a lower suction pressure, so once that was corrected that could explain why some of your numbers are simply higher now. It does not explain however the difficulty changing MPV settings or seeing that filter lit rise a little. Even with a filter pressure of 19-20 psi, that shouldn't be enough to cause that issue.

 

[Stefany]

Stefany, just a reminder, I notice you have a salt pool (SWG) so please add that to your signature along with your test kit and all of your pool details. It would sure help us as we review each post.

I have re-read your last post with all the info. If I focus on the "Pressure Data" chart above and focus on the tank (related to endless feature I'm assuming) and main drain pressures, those pressures are consistent. You mentioned earlier you thought maybe the pressure changes started after replacing the valve before the pump since it was leaking. That leaking valve would've results in a lower suction pressure, so once that was corrected that could explain why some of your numbers are simply higher now. It does not explain however the difficulty changing MPV settings or seeing that filter lit rise a little. Even with a filter pressure of 19-20 psi, that shouldn't be enough to cause that issue.

Hi,

Yes, you're right, as we cannont find a solution , I will ask again the service team to come back for inspection (and repair a new problem (see below).

One interesting thing your wrote, is the fact that this "high" pressure around 20psi wouldn't be enough to rise the filter cover. It's my own conclusion. Pressure is too high for a reason we cannot find at the moment, but something happens at the same time with the filter lit (I think I will post a new thread about this issue). As you told me and as I wanted to do , I have just opened the filter (pump stopped, all valves and return closesd, MPV in filtration position) and had a look of the cover, o'ring, sand and connecting pipes. Nothing wrong so I've closed the lit (not too tight) and a second later when I've wanted to check if the lit was tight enough, it exploded

At this moment, the filter was quite full of water but all the valves were closed (not the MPV, it was in filtration position) so there was no more water (or air?) coming through the filter.

This is the second time in one month such accident happens. When we replaced the filter lit, it was because the maintenance team checked inside the filter, installed the lit and the lit exploded exactly the same way and at the same moment (when they were verifying if it was tight enough !). I remember too that I have had to replace 2 times in the last 2 or 3 months the lit pump o'ring, because lit was very difficult to open and when I succeeded, o'ring was expanded !

Filter can resist 35PSI, so when the pressure is 20PSI, it's sure it's high but as you told, not enough to rise the lit or damage the filter.

Something very odd happens, but what?

I noticed when I close the MPV, the water from return pipe (valve opened) comes trough the MPV and goes to filter, not the water from the pump. Maybe it's alright, maybe not, I don't know.

I called the maintenance team, but I do doubt they will do better than last time. I don't know what to do after exploring so many solutions and false leads. It seems hopeless.

 

[Stefany]

Hi,

Has anybody experienced explosion of sand filter lit? It happened to me 2 times in a month.

For a few weeks I have been checking my system everyday because of a high pressure problem (about 20 PSI and the pressure doesn't decrease after backwash, water lealing now from the filter lit). I was there, checking everyday with an helpull TFP member how to solve the problem, concluding that even if the pressure was to high for some unknown reason, this high pressure couldn't rise the filter lit, made it leaking.

So a few hours ago, I opened again the sand filter lit (pump stopped, all valves and return closed, MPV in filtration position) and had a look of the cover, o'ring, sand and connecting pipes. Nothing wrong so I've closed the lit (not too tight) and a second later when I've wanted to check if the lit was tight enough, it exploded.

At this moment, the filter was quite full of water but all the valves were closed (not the MPV, it was in filtration position) so there was no more water (or air?) coming through the filter.

This is the second time in one month such accident happens. A month ago, due to the high pressure problem, I have had to replace the filter lit because the maintenance team checked inside the filter, installed the lit and the lit exploded exactly the same way and at the same moment (when they were verifying if it was tight enough !). I remember too that I have had to replace 2 times in the last 2 or 3 months the lit pump o'ring, because lit was very difficult to open and when I succeeded, o'ring was expanded !

Filter can resist 35PSI, so when the pressure is 20PSI, it's sure it's high but as you told, not enough to rise the lit or damage the filter.

Something very odd happens, but what?

I noticed when I close the MPV, the water from return pipe (valve opened) comes trough the MPV and goes to filter, not the water from the pump. Maybe it's alright, maybe not, I don't know.

If anyone has ever had this problem, I would be very interesting to know it, because as I have checked for weeks without success the high pressure reason, now a new problem occurs maybe linked maybe not, but a very dangerous one so I must try to solve it as soon as posible.

Please see pictures attached and thank you for beeing indulgent with my spelling and words (french woman in american forum is not easy)

 

[Texas Splash]

Something is definitely not right with that unit if the lid is popping off at only about 20-30 psi. Even on their website HERE they show a pressure gauge that goes up to 50 psi. You would never want it that high on purpose, but it should be able to retain the pressures you noted. There must be a restriction either in the filter or beyond. Something assembled wrong in the filter, or a closed/defective valves after the filter.

On a side note, @JamesW do you have experience with this make/model filter?