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How to Correct Low Water Pressure in Your Pool System

WRITTEN BY: Inyo Pools

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Low pressure is a pool term that is often used to describe weak jets as well as a low PSI reading on the filter’s pressure gauge. High PSI readings will also cause low water pressure. A low or high PSI reading is anything outside the normal operating pressure of the filter. Weak jets, air bubbles, slow pool cleaners and weak water features are obvious signs of low pressure. This guide addresses the common causes of low water pressure in a pool.

Step by Step

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Step 1

Your pool’s plumbing system can be broken into two sections: the Suction-Side and the Pressure-Side. The Suction-Side of your pool includes the skimmer, main drains, plumbing, and any other equipment like diverter valves, up to the strainer housing of your pool pump. The Suction-Side is the portion of the system, your pump is pulling the water toward it. The Pressure-Side of your pump begins at your pump’s impeller; this is when the pump’s pulling becomes a pushing force to move the water through your pool filter, heater, chlorinator, and all the associated plumbing until it returns to the pool via the return jets.

Step 2

Low Water Level (Low PSI) - The water level should be at least halfway up the skimmer door opening. A low pool skimmer water level will allow the skimmer to gulp air as your water ebbs and flows caused by the pump running or activity in the pool.

Step 3

Clogged Skimmer Basket (Low PSI) - If your skimmer basket is full of debris, you are effectively shutting off the pipe between the skimmer and the pump. Generally, this will reduce the flow of water to the pump. If the pump has less water entering it, it is moving less water out. This means the pump is doing less work that in turn will reduce water pressure.

Solution: Clean your skimmer basket by removing any debris.

Click Here to View Replacement Skimmer Parts

Step 4

Clogged Strainer Basket (Low PSI) - It is the same story as above. A clogged strainer basket means less water flow that leads to less water pressure out the returns.

Solution: Clean your strainer basket by removing any debris.

Click Here to View Replacement Pump Parts

Step 5

Clogged Filter (High PSI) - Again, if water can't get through a clogged filter, you will have less water flowing out of the filter. Incidentally, this will increase the water pressure in the filter signaling that it is time to clean the filter.

Solution: Wash your cartridge filter. Periodically soak the filter overnight in a TSP solution to get the grease and gunk out of the folds. Grease is produced by suntan lotion, sebum (oils secreted by the human body) and pine tree needles. Then soak the cartridge in a weak solution of muriatic acid (10:1) to get the minerals out of the folds. Use the TSP before the acid or the gunk will set up in the folds. For sand filters you will need to backwash as required. Change the sand every five to seven years. In between changes, if sand has caked on top, take one to two inches off at the top and replace it with new sand.

Click Here to View our Liquid Filter Cleaner

Click Here to View Replacement Filter Cartridges

Step 6

Clogged Impeller (Low PSI) - This problem is often overlooked. If the impeller becomes clogged with debris, water can't rotate out the sides of the impeller. This decreases suction which reduces water flow through the pump.

Solution: Clean out the impeller. See our guide on "How To Clean Out a Pool Pump Impeller".

Click Here to View Replacement Pump Parts

Step 7

Suction Leak At Pump (Low PSI) - The pump lid o-ring, pump intake fitting, and drain plugs are common areas to draw in air. A suction leak in the suction side of the pump can cause a number of problems. If it's large enough, too much air will be sucked into the system, and the pump will lose prime. If it's smaller, air will be sucked in through the pump and start to collect at the top of the filter tank. After some time (sometimes a few hours) air pressure at the top of the tank will create enough back pressure to reduce the flow of water significantly. When the pump is shut off, this back pressure will cause the water in the suction pipe to surge back and sometimes create a column of water up though the skimmer.

Solution: Find the suction leak and close it. See our guide on "How to Identify and Correct Air Leaks".

Click Here to View Replacement Pump Parts

Step 8

Suction Leak at Diverter Valve (Low PSI) - The diverter valves in front of the pump control the flow of water from the skimmer, main drain, and vac lines. They also have seals in them that can go bad and allow air to enter the system. Again, air will cause the water pressure to drop and will lead to the pump losing prime.

Click Here to View Diverter Valve Parts

Step 9

Suction Leak At Plumbing Fittings (Low PSI) - Any fitting on the suction side of the system can draw air. Cut out and replace any fittings that have an air leak.

Step 10

Clogged Pipe Going To The Pump (Low PSI) - A clogged pipe from the skimmer, suction line or main drain reduces the amount of water to the pump which can reduce water flow to the pump and create low water pressure out the return lines.

Solution: Push a stiff wire down the skimmer or suction ports to see if you have a clog near the entrance. If there are no clogs there, you may have to get a pool professional to come in to check your pool pipes.

Step 11

Too Many Features Opened - The pump is only designed to move so many GPM. Too many water features are like too many hoses on a sprinkler system. The first one has great pressure. Subsequent hoses will reduce the water pressure.

Solution: Alternate which features are turned on or replace the motor in your pump with a larger one. Make sure your existing filter will support the larger pump. You may also have to replace it.

Step 12

Pump Is Too Small - If your pump's size was calculated for you initial pool system and you have added more equipment onto that system, you may have exceeded the pump's capability to supply the GPM that is now required. Also, if you have moved your pump significantly further away from the pool, which required more pipe, you may have increased water resistance in the pipes that exceeds the pump's capability.

Solution: Replace the motor in your pump. Note you may also have to increase the size of your filter if it won't handle the increased GPM water flow. See our guide on "How To Replace the Motor on Your Pool Pump".

Click Here to View Replacement Pool Pump Motors

Step 13

Bad Pressure Gauge - Pressure gauges on top of the filter do go bad. Your apparent low-pressure reading may be due to a faulty gauge.

Solution: Replace the pressure gauge. See our guide on "How To Replace a Pool Filter Pressure Gauge on a Cartridge Filter".

Click Here to View Replacement Filter Parts

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(321 to 360 of 373)

InyoPools Product Specialist Dennis R. Posted: 6/12/2015

Renee - Many filters have a breather tube from the bottom of the tank to the top. The purpose of the tube is to purge any air that might be trapped in the top of the tank causing back pressure. Check to make sure this tube or the screen capon top is not blocked.
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Renee Posted: 6/11/2015

I have a namco pool, pipeline (older) filter and pump. We have checked everything! The pool will run great for about 15 mins with good water pressure out the pool jet To circulate the pool. After that the pressure in the filter increases to 20-23 and we lose pressure. We have changed DE, put less in. The pump looks to be running fine, but something in the filter seems to be clogging? Please help, desperate.... Thank you
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InyoPools Product Specialist Dennis R. Posted: 6/9/2015

Koltzfan - When you replaced the multiport valve (MPV), did you replace it with the correct MPV? With some manufacturers, the water flow through a DE MPV is different than the flow through a sand MPV. If that's not the problem, check the MPV spider gasket to see if it was damaged and blocking the backwash port. While you have the MPV apart, look and see if something is blocking the Waste port.
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Koltzfan Posted: 6/9/2015

Replaced the lateral assembly, multi-port valve, and sand. Made sure covered stand pipe sa not to get any sand in when replaced. Turned pump on and run between 8-10 PSI in filter mode. When I try and backwash it's only a little water and no pressure on discharge side.
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InyoPools Product Specialist Dennis R. Posted: 6/8/2015

Maggie - Check you pump's impeller to make sure it's not clogged - see "How To Clean Out a Pool Pump Impeller". Then see if you have developed a suction leak in the connections between the pool and the front of the pump. One way to do this is to pack plumber's putty on the outside of each suction connection. If the pump maintains prime , go to the last connection packed for your leak.
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Maggie Posted: 6/8/2015

Were just getting our above ground pool ready for the summer. we only installed the pool last year. When we started the pool everything was fine but now for some reason were not getting any pressure on our filter. The pump basket seems filled with water but when I start the pump it looks like it fills so far and then lets water back out.....like a sucking sound. The water in the skimmer isn't moving at all and the return on the pool seems to be sucking it back and than pushing it out a little. I've checked both baskets and seem fine. It's strange because it was working before to where I could clean the pool. Any help would be great....
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InyoPools Product Specialist Dennis R. Posted: 6/6/2015

Atwaterdan - Sounds like you may be overloading your filter with too much algae/debris. Try vacuuming the bottom algae/debris and dumping it out the waste line - bypassing the filter. You will have to replace the water. At some point stare filtering again. You may have to clean your filter 3-4 times a day so that it isn't completely blocked by the algae/debris while you are getting rid of the algae.
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InyoPools Product Specialist Dennis R. Posted: 6/6/2015

Bobbybones - If you aren't getting either air or water out of the top relief valve, your valve may be clogged. The air has to be coming out or the system is just building back pressure in the top of the filter tank. Check if the valve is clogged. Also many filters have a breather tube from the top of the tank to the bottom top relieve pressure. Make sure that tube is clear. If this doesn't solve your problem, I would look for suction leaks in the connection between the pool and the front end of the pump.
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Atwaterdan Posted: 6/5/2015

FRUSTRATED: I have a vinyl 20k gallon pool. Hayward .75 hp pump and Spa-rite single paper cartridge which Leslies say is the correct filter (It is new). I cannot get any pressure to register on new pressure valve....and no water will bleed out of the top valve when pump is on. Skimmer is drawing well and when I clean the filter every 24 hours it is solid green.....so something is working...trying to clean up green pool.....clean impellers on pump and outlet has strong flow.....can I just chalk this up to a mystery and not worry...or am I being ineffienct.....seems like I am not making much headway cleaning out green stuff...it has been two weeks with all proper chemicals...Leslies just says keep sweeping and treating............HELP
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Bobbybones Posted: 6/5/2015

Hey I have a problem with no pressure at all. I back washed and put in new de sand, and I see the sand go up into the small skimmer by the pump. But there it slows down. Now the sand eventually got pulled through and I have normal water going back into the pool. No sand or debris showing in the pool. I have the valve on top open so the air can escape and the filter can fill up with water like normal, but no air or water is going through. It seems the filter can't hold water to full capacity. Help please!
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InyoPools Product Specialist Dennis R. Posted: 6/4/2015

LONELADY - I have not heard of this problem before. If this occurs when the filter is in Recirculate mode, if must not involve the filter because Recirculate bypasses the filter. It sounds like when the pressure gets to 5 psi, a suction leak opens up and your pump loses prime. I would check all connections from the pool to the pump - suction side. One pool owner did this by temporarily packing plumber's putty around the outside of each connection one at a time. When the pump maintained prime, he knew that the last packed connection had the leak.
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LONELADY Posted: 6/3/2015

I have a Hayward maxflo pump with sand filter. The pressure continually cycles and will not hold. Pressure will be at zero and then the pump basket slowly fills with water until it hits 5 and is running normally then immediately the pressure bottoms out and the water drains and then the cycle starts over. I have checked both baskets and tried to fish around with the impeller but found nothing. The same thing happens whether it is filter/backwash/recirculate. Any suggestions, and am I damaging my pump by continuing to run it?
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InyoPools Product Specialist Dennis R. Posted: 5/25/2015

low pressure - Most filters have a pressure relief tube that goes up from the bottom to the top of the tank. Make sure that tube is not blocked. Also, check your impeller. Low pressure is often caused by a clogged impeller in the pump.
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Anonymous Posted: 5/22/2015

need help,we have an inground pool with a DE filter, our pool pressure isn't as strong as it used to be. when trying to vacuum pressure drops down to zero and connection releases. Also when the pump is turned off the water in the filter is backing up into the filter basket. Is there something we can do or is it time to replace the system?
Reply

InyoPools Product Specialist Dennis R. Posted: 5/6/2015

tc - Have you checked the pump for a clogged impeller. This has been the source of many problems like this. See our guide on "How To Clean Out a Pool Pump Impeller".
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tc Posted: 5/5/2015

Help. I dont know where to go with this. The pressure on my filter generally starts at 9 lbs when I backwash the filter. I usually backwash again when this gets to 18 or20. Now my pool is cloudy and when I vacuum it , the pressure goes down. The pressure won't build up. The water flow out of the return lines is still good. Almost like it's bypassing the filter completely. I've changed the filter medium (300 lbs of sand) and the pressure gauge. I don't see any visible cracks in the filter or the dirverter valve. The cloudy water and the pressure issues showed up at the same time so I think their related. I would rather not replace the filter and valve until I'm sure it's necessary. The pool was installed 10 years ago and this is a new one for me. What could the pressure to drop when the valume of water is normal? A secret bypass I don't know about? Any comments or suggestions would be greatly appreciated.
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Anonymous Posted: 4/14/2015

Pool pressure was at 5lbs trash at the pump cured it thanks
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InyoPools Product Specialist Dennis R. Posted: 3/23/2015

low pressure reading - It's not clear if your pressure is low or you are just seeing a low reading due to the broken pressure gauge. I would replace your pressure gauge first to see what the actual pressure is. See our guide on "How To Replace a Pressure Gauge on a Pentair Triton 2 Sand Filter". If your pump is maintaining prime, the small leak in front of the pump is probably all right. Replace the piping if that gets worse. As to replacing the filter sand, that doesn't seem to be the issue if you see no difference on recirculate. However, if you haven't changed your sand in 5-7 years, you should change it. See our guide on "How To Change Sand In a Sand Filter". If you actually have low pressure, I would check to see if the motor impeller is clogged. That is a common problem. See our guide on "How To Clean Out a Pool Pump Impeller".
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Anonymous Posted: 3/22/2015

Pressure gauge is broken and there is a small leak where the pipe goes to the filter basket. We tried the recirculate tip and we get the same amount of pressure as when on filter. They are telling us that we need to replace the sand in the filter; any thoughts or suggestions would be helpful. We are wondering if we should just put a new pressure gauge on or replace the entire filter system?
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InyoPools Product Specialist Dennis R. Posted: 3/16/2015

helpus! - You may have a badly clogged filter. Put the Multiport valve (MPV) in "Recirculate" mode. Remember to turn off the pump first. In recirculate mode the MPV bypasses the filter and goes directly from the pump to back to the pool. If you get water flow, it probably means the sand in your filter needs to be changed. See our guides on "How To Change Sand In a Sand Filter" or "How To Replace the Sand in a Pentair Triton 2 Side Valve Sand Filter". If you have no flow on "Recirculate", you have a blockage in one of your lines.
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helpus! Posted: 3/15/2015

We bought a house with a pool that was half drained and green. We've spent all weekend cleaning it up. Now that it's clean, we tried to run the filter. It turns on and sounds like its working, but no water is cycling back into the pool from the sand filter. What might the problem be? We've checked any blockages in the skimmer and pump.
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InyoPools Product Specialist Dennis R. Posted: 3/15/2015

PoolMama - Sounds like you still have skimmer problems. Fill your pool up a couple of inches to get it above where the skimmer leak might be. Then, with the pump off, place a couple of food coloring drops around the skimmer and see if that identifies where you might still have a skimmer leak. Food coloring drops will go to leak.
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PoolMama Posted: 3/11/2015

I have a saltwater in-ground pool which is about 30 years old. We upgraded the main pump last year to a Pentair Intelliflo. It has a Jet-Vac cleaner which still uses an old Hayward pump. We have an ongoing leak as the skimmer separates from the pool. We have to epoxy it at least once a year. We had to do that recently (the water had gone down to a couple inches below the skimmer opening and then stayed there) then got the water up to the right level. Everything was working great. I added a bunch of salt to get the levels back up. The saltwater system was generating. The chlorine levels were rising. I added stabilizer. There was a lot of algae and debris in the pool due at that point. I was emptying all the filter baskets frequently and backwashing the filter (a DE system in which we are using cellulose). After backwashing, I added a little more cellulose. All good. Then I noticed the Jet-Vac stop working and a whole lot of air came out of the Jet-Vac and the return that it attaches to. I let the air out of the system and checked the pressure. Everything looked fine. Well, there's always extra air in our system which I let out whenever I notice the pool is not working well or have any sort of maintenance to perform. Then I got caught up in other things and didn't look at it for a day or two. When I did, the water level had fallen down to the bottom of the skimmer opening (not 2" below as it was before we epoxied the skimmer) and it has stayed there for several days. The epoxy fix to the skimmer appears to be very solid. I can't run the pool right now because the water is too low and I'm loathe to top it off if it's just going to run out again. Any thoughts? We know we need a new skimmer when we can afford it. We really hope to avoid the pool leak detectors in our area who charge and arm and a leg. Thanks so much for any advice you may be able to offer. I did sign up to get your free pool book download, so feel free to refer to specific places in the book if it helps.
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InyoPools Product Specialist Dennis R. Posted: 1/18/2015

70mach1 – I don’t understand what caused the hydro shock but it does sound like you blew one of the gaskets or o-rings on the suction side of the pump.
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70mach1 Posted: 1/15/2015

My inground pool had a leak in main drain so I had it plugged. Then the pump would not prime, so I used a plumbers bladder to force air from the skimmer to the pump basket. Got a lot of debris from the line. Afterwards the. Pump primed better and I thought I would try moving the Henry valve back and forth to try to dislodge any remaining debris in the line. When I did this, there was a very large hydro shock sent into the pump basket and now the pump will not fully prime again. What, if any, damage might I have done to the pump. I have taken it apart and cleaned out the centuries and impeller. Pump seals bad perhaps?
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InyoPools Product Specialist Dennis R. Posted: 1/15/2015

mumcleansthepool - Sounds like you have a leak in the dedicated suction cleaner line. Check to make sure there are no leaks in the cleaner hose connections. Separate the last length of hose next to your suction port. Plug one end into the port and hold the other end under water. If your pump maintains prime, you have a leak in the rest of the hose.
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mumcleansthepool Posted: 1/14/2015

I have fine suction when not vacuuming the pool. But as soon as I plug the cleaner in, suction goes almost to nil and strainer basket is void of water. Both the skimmer baskets and strainer baskets are empty and the sand filter has been backwashed.
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Pool Dad Posted: 8/31/2014

Sometimes you need a refresher course in the basics! Had to disassemble the impeller housing to completely remove all of the debris. Not the first time I've had to, hopefully the last!
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InyoPools Product Specialist Dennis R. Posted: 8/17/2014

low pressure - If your pump is maintaining full prime (minimal bubbles) and your jets have good pressure, I would question the pressure gauge or pressure monitoring system. You can't have good system pressure with a faulty filter.
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Anonymous Posted: 8/15/2014

I have a salt water pool. My sand filter pressure was high and I backwashed and rinsed. Now the pressure is between 0 and 5 and goes back and forth not getting higher than that. I have checked the skimmers, the jets have pressure just the filter itself is not getting enough. What else can I look for to solve this problem? The red light goes back and forth from good pressure to no pressure and it also shows low on salt which I added the salt needed. Any help will be greatly appreciated. Thanks
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InyoPools Product Specialist Dennis R. Posted: 8/3/2014

Low Pool Pump Pressure - Sounds like your suction lines are OK. You may have a blockage in the common pipe between the diverter valves and the pump. If you had a blockage on the discharge side of the pump [at your heater], I would think your pressure on the gauge would go up. Did you check for a blockage in you pump's impeller? Or your pressure gauge may be faulty.
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Low Pool Pump Pressure Posted: 7/31/2014

I have two lines...skimmer and main drain. If a line was clogged/blocked wouldn't the pressure be stronger on the one line and lower on the clogged line? I have a shut off valve for my main drain and the skimmer, when I shut the main drain valve off and run on skimmer only, I only have 2-1/2 psi, if I shut the skimmer valve off and run the filter from main drain only I have 2-1/2 pounds of pressure. With both valves open the system is running on 5-8psi.
My pool filter system has a gas heater, which I don't use...is there a possibility that there could be a clog there?
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InyoPools Product Specialist Dennis R. Posted: 7/29/2014

low pressure - The only other thing I can think of is you might have a blocked pipe somewhere. Try running a plumber's snake though some of the lines.
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InyoPools Product Specialist Dennis R. Posted: 7/28/2014

Breskeeper1966 - If the level of water in you pool went down significantly while your pump was off for 15 hours, I would think you have a leak in your pool somewhere. The water had to go somewhere and it wasn't into your pool system above the pool level.
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Anonymous Posted: 7/28/2014

Hi. I am at my wits end with my pool. My in the ground pool is green and I only have 5psi reading on my pressure gauge. The pool is 12 years old with a sand filter system. I have no bubls coming out of my return lines, I just installed a new Pentair 1hp pump, thinking that would resolve the problem. The pump is working great, no air bulbs appearing in the secondary basket. I have also changed the sand in my filter tank and checked the laterals, they are all good. The gauge is in working order. Please help! I'm running out of things to check on the filter system.
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Breskeeper1966 Posted: 7/27/2014

I have a question. We had a bad storm last night so I turned by filter off by turning the switch off at the electronical box. Had things to do and went out to my pool after the pump and filter being off about 15 hours and I've lost major water. Can someone tell me if this is something that happens when the filter and pump are turned off for long period of times? Or do I have a whole new problem?
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InyoPools Product Specialist Dennis R. Posted: 7/21/2014

nictali - Check for a clogged impeller. That's a common problem, especially if you're near pine trees. Then, if you haven't replaced your sand in 5 years, try replacing the top 6" on see if that improves your pool's water pressure.
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nictali Posted: 7/21/2014

The pressure in my pump was fine when I opened the pool, was trying to clean, put it on waste, hardly any suction, now hardly any pressure in the pool. The jets are barley shooting any water out. Can use any suggestions
Thanks
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docscottu Posted: 7/14/2014

clogged impeller for me. thanks dude. solved the problem immediately. easy fix too. much appreciated
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Just Me Posted: 7/12/2014

Thank you so much for this info. I have been struggling with the pool for a two weeks, would work sometimes then sometimes would be impossible to prime or get the right suction. There was debris in the impeller, wonderful pine needles from the neighbors tree. Searching for clues online was my last attempt before calling repair man. Saved me a bundle I'm sure!
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