FIXED: Polaris 3900 was lazy and tail did not sweep (2022)

3 years ago my old Polaris 280 had a number of problems, and on the advice of a pool maintenance company I bought a new Polaris 3900. However, I was never very happy with it because it was not "peppy" -- seemed to crawl around where the older model zipped -- and the tail never really swept at all, where on the 280 the tail had been very effective at brushing the walls and sweeping debris to the drain.

The thing was serviced by a maintenance company at the beginning of each season, but the problems just never got any better. This year the problems were noticeably worse, to the point where the corners of the pool were collecting dirt lines that never got swept away. However, the (new) pool company took a look and claimed that there was nothing wrong with the Polaris, and that this is just an underperforming model.

Last week I finally had some little free time so I decided to do some research into the problem. I found hundreds of owners complaining online of the same problems, but I didn't find anybody with a solution.

I counted the wheel rotations and found only 22 RPM where the expected speed is 32-34 rotations per minute for the large wheel (per the user manual). I disassembled the 3900 and did not find any obvious problems, so I called Zodiac.

(Video) Lethargic Polaris 3900

The nice man at Zodiac told me to remove the flow restriction disk installed at the wall -- but of course there is no flow restriction disk installed. Then he told me my Polaris booster pump was not producing enough pressure or enough flow to drive the 3900. This was not a reasonable suggestion, because the pressure release valve at the wall was blowing off a LOT of water and the flow was more than sufficient to make the backup valve work perfectly. So I thanked the nice man and hung up the phone. I realized that I would have to solve this problem myself, so even though I was pretty sure the booster pump was putting out plenty of water at a high pressure, I decided to prove or disprove this definitively before looking inside the 3900 for some kind of subtle problem.

I learned from another nice person at Zodiac that the 3900 requires 8-10 Gallons per minute at a pressure of 32 - 34 PSI when measured at the end of the supply tubing (after the backup valve).

I went on Amazon and ordered a combination pressure and flow meter (built by Toro). It arrived in just 2 days even though it wasn't sold by Amazon directly. This is a light-duty meter intended for occasional use with a hose bibb. It has a hose faucet connector, so I cut one end off an old garden hose, screwed it onto the meter, and clamped the open end of the garden hose directly to the Polaris backup valve (the inside diameter was a perfect fit, but the screw-on tightener is designed for the thicker wall of the polaris hose, so I used a hose clamp to make sure it didn't blow off under high pressure).

I turned on the booster pump and closed the flow control knob completely, and found that my static pressure was 60PSI -- that's pretty high -- and when the flow control knob was opened enough to allow a flow rate of 8 GPM, the pressure was 34 PSI, which is exactly what the 3900 requires. Just for interest, I also checked the pressure before the backup valve, and found that the backup valve itself introduces a drop in pressure of about 5 PSI, presumably due to flow restriction from the internal mechanism.

(Video) Fixing a Polaris Tail Sweep, Pool Cleaner

With plenty of flow at the right pressure entering the "critter," the problem had to be in the 3900 itself.

I took it apart again and this time I went over everything with a fine tooth comb, and with the absolute conviction that the problem was somewhere inside the critter. Armed with those tools and a magnifying glass, I did in fact find several problems that had not been immediately obvious.

The first problem was that the tail flow control assembly had two O-rings installed where there should only be one. This actually prevented the flow regulator from down-regulating the flow to the tail, and also made it extremely difficult to turn the tail sweep control valve at all -- something I had noticed from day one. OK, one definite problem resolved, except that this fix still would not help me create *increased* tail sweep -- I would now be able to turn the sweep down, but I needed to turn it UP. I looked more closely at the mechanism of the sweep flow control. Basically, there are two plastic surfaces pushed against each other, each with a small half-circle cut out to allow water through. If the tail control is rotated so the two half-circles line up, the maximum amount of water comes through. If one piece is rotated 180 degrees, the two half circles will not overlap at all, and no water will come through.

I connected the tail assembly (with tail) to my flow measuring apparatus and turned up the pressure. The Polaris 3900 water management system delivers flow to six places: three cleaner siphon ports, the wheel drive, the balance jet, and the tail. But even when I gave the tail a full quarter of the total rated pressure, the water that came out was not up to the jet force and volume that I was used to seeing with the old Polaris 280. It seemed to me that the holes feeding the tail are just too small to allow enough flow through at the pressures being supplied. Therefore I decided to enlarge the two holes so that more water would come through when they were aligned. The alteration would mean that I could still turn down the flow, but I could no longer completely shut off water to the tail -- but why would I ever want that? I took a small file and enlarged the holes by about 30%. Instead of two half-circles, they now looked like slightly flattened footballs.

(Video) How to Repair Polaris 3900 When Wheels Are Locking up

OK, the tail will get more water when turned to max open, and I can still turn it down most of the way if I need to. Now to debug the overall peppiness issue.

Since the wheel is driven by a jet of water that pushes a water-wheel, there had to be a loss of pressure somewhere in the circuit before that jet. I plugged all the holes in the lower water management system and blew into the device, and there were no leaks. I hooked up my flow pipe directly to the lower WMS to drive the jet directly, and -- wow -- the wheels turned like crazy when I put the rated pressure/flow into the WMS. I plugged the upper supply tube and blew air into it, and there were no leaks. That only left the connection between the upper supply tube and the lower WMS. This is an O-ring joint, and I inspected it closely with a lighted magnifier. Lo and behold, the slip joint itself is just a teensy bit loose, and (more importantly) the O- ring that was installed was not *quite* the correct size for the joint. The O-ring was just a little bit larger diameter than its intended seat, and also somewhat narrower than the bed it should have filled. Under magnification I could see areas where the O-ring had become crimped by being squeezed out of its bed. Just looking at it you would not be likely to think anything was wrong -- it hardly looked like enough to make any difference at all. Surely we couldn't be getting much loss of pressure through such a tiny gap? But of course we could.

I went to the hardware store and bought a correctly-sized O-ring and installed it. Then, since I happened to have the slightly over-size O-ring already in my hand, I slid it up inside the upper water supply tube to serve as a compression gasket between the lower water management system and the upper supply tube -- it snugged up in there very nicely, and even though it's not part of the original design, it can serve as a fail-safe in the event of leakage around the primary O-ring.

I did also put a little bit of stopcock grease on all of these surfaces (I have a tube left over from a chemistry lab I had back in 1976, and have found that the stuff works great in harsh marine environments).

(Video) Pressure Pool Cleaner Troubleshooting Tips

Put everything back together, and fired it up, and got a big smile on my face as I watched the little critter go zipping around the pool, lashing its tail exactly the way I had been hoping. I swear, I felt peppier myself just watching it. And in fact my wife sat and watched it perform for about a half hour before she pulled herself away.

So bottom line: I think this thing probably came from the factory with the wrong size O-ring installed in the main water supply junction to the WMS, and with two O-rings instead of one in the tail valve assembly. For sure it came with the wrong size flow adjustment holes designed into the tail valve control mechanism. The original over-large O-ring worked semi-adequately when it was new -- it leaked enough to make the 3900 sluggish compared to other models, but not enough that it failed to clean the pool. Over a couple of years it got slightly extruded and a little bit stiff, and the leakage became worse to the point where the poor little guy was really anaemic and had low blood pressure!

If you have the same sluggishness problem I was experiencing, start by installing the right O-rings -- don't get a replacement for what's already in there, get one that really fits snugly and fills the ring bed. Then if you want more tail action, go ahead and file both half-moon holes a little larger (doing just one won't change anything). The tail modification works perfectly for me -- if I rotate the valve counter-clockwise the tail just lies there, and if I rotate it all the way clockwise it lashes like a live animal. I think Polaris ought to modify this part of their design, but TJMO FIXED: Polaris 3900 was lazy and tail did not sweep (1)

BTW, I also learned that there is an add-on tail tip available that will stop the tail from spraying water out of the pool when the critter climbs the wall and then dives back down. Recent models come with this already installed, but mine did not. At one time I might have wanted that feature, but after several years of lackadaisical tail droop, I'm kind of enjoying the occasional spritz, and the shrieks when somebody fully dressed gets unexpected attention from the critter FIXED: Polaris 3900 was lazy and tail did not sweep (2)

(Video) Changing the Polaris 3900 sport (P39) RO538000 Head Float - Requires Cleaner Disassembly

That's my story and I'm sticking to it.


How do you adjust the tail sweep on a Polaris 3900? ›

To adjust the motion, turn off the booster pump and turn the sweep jet clockwise to increase or counter-clockwise to decrease the movement. Detach the Velcro strips. Twist the bag collar and pull up to free the bag from the cleaner.

How do you adjust a Polaris tail sweep? ›

Control the Sweep Tail Movement

Simply turn off the booster pump and turn the cleaner's sweep jet clockwise or counterclockwise (depending on your issue). Doing so should get the sweep tail on your pressure-side pool cleaner to move in a gentle sweeping motion.

Why is Polaris pool cleaner not moving? ›

If those ball bearings can't roll, the connectors can't swivel, the hose can't move properly, and you have a tangle on your hands. Check the connectors to ensure they move freely. If they don't, apply a little waterproof lubricant to ball bearings. If this doesn't help, you may need to replace the connectors.

Why won't my Polaris pool cleaner stay on the bottom of the pool? ›

A dirty debris bag can be the source of your issue. Even microscopic debris or biofilm can be enough to trap air in the bag and cause it to float. Try running the cleaner without the bag to see if it still floats. If it doesn't, then you just need to clean your bag.

Why does my Polaris stay in the deep end? ›

This could happen with 80 series (booster pump) or 60 series (return hook-up). Check all the hose swivels and connections to make sure you are not loosing too much water. A good way to check all this at once is to pull the cleaner near the surface of the pool while running and check the rpm of the wheels.

Why does my Polaris stay in one spot? ›

“The Polaris is staying in one spot or one end of the pool” Be sure to check: If the swivels leaking. These are in the hoses, and look like joints. It okay if the swivels slightly leak, but anything more than a steady drip it will need to be replaced.

Should water be coming out of Polaris pressure relief valve? ›

Nope, it's doing what it's supposed to do....the pressure relief valve is supposed to let out whatever excess water pressure your polaris does not need. So, if you want it to stop "leaking" you can send less water to the polaris return, but then you run the risk of the unit not getting enough pressure.....

Why does my Polaris tie itself in knots? ›

Improper Hose Length: Excess length can cause the hose to tangle and make it impossible to untangle itself with its swivels. How to fix it: While the hose is connected, walk around to the farthest point of your pool. The hose end should be within six inches – longer or shorter – of the farthest point.

Where Should Floats be on Polaris hose? ›

The Polaris in-line back-up valve and float should be installed 30" from the Polaris. Once installed, the hose should look like the one below. 1.

Why does my Polaris pool cleaner go in circles? ›

Most of the time, pressure cleaner circling is caused by too much flow coming into your cleaner. So, you simply need to adjust the flow coming into your cleaner.

How do you adjust a Polaris pressure relief valve? ›

It can be manually adjusted by screwing it in our out of the wall fitting housing. Screwing it all the way in give the Polaris the maximum amount of pressure and speeds it up, unscrewing it will relieve the pressure and slow the cleaner down.

How do you troubleshoot a Polaris booster pump? ›

Examine the pump at the intake and outlet for any leaks. If the pump has an installed valve, make sure the valve is open and working properly. Inspect the impeller for debris. Make sure the discharge of the booster pump is not plumbed into a normal return line, but correctly plumbed into the dedicated cleaner line.

Why is my Polaris 3900 floating? ›

Leaks in the Polaris hose cause the cleaner to lose pressure, allowing it to float above the pool bottom. To check for leaks, turn the system on and pull the hose out of the water one section at a time, looking for bubbles or trickles of water.

How long does a Polaris pool sweep last? ›

You can expect the device to serve you for four or five years. It can even last up to eight years with the right upkeep. Although you can find cheaper models that do not offer the same lifespan but given the proper care, you can still expect them to run for at least three years.

Should you leave Polaris in pool? ›

Pressure cleaners shouldn't be left in the pool 24/7 because it increases their exposure to chemicals in the water that can corrode the cleaner over time. You should always remove the cleaner from the pool when adding large amounts of chemicals to the water.

Should you leave Polaris in pool? ›

Pressure cleaners shouldn't be left in the pool 24/7 because it increases their exposure to chemicals in the water that can corrode the cleaner over time. You should always remove the cleaner from the pool when adding large amounts of chemicals to the water.

What does Polaris tail do? ›

The Polaris Tail Sweep Pro is a retrofit accessory that can be easily added to any 3-Wheel Polaris pressure cleaner. Not only does it keep your Polaris pool cleaner from spraying water out of the pool but it also enhances scrubbing action and maximizes water propulsion to blow debris out of corners.

How do you troubleshoot a Polaris 280 Pool Cleaner? ›

Troubleshooting Pressure Side Pool Cleaners (Polaris 280 & 380)
  1. Check the wheel RPM (rotations per minute).
  2. Verify the back-up valve is cycling.
  3. Adjust the thrust jet.
  4. Remove unnecessary pool hardware or install a ladder guard kit (Sold at our retail stores).

What type of Polaris do I have? ›

The newer Polaris cleaner models have the serial number stamped on a sticker on the back of the cleaner. If the serial number starts with a “K” it will be a 380, if it starts with “C” it will be a 280, if it starts with a “L” it will be a 360.


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