Sand in guts of Polaris 380 - source? and how to stop?

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Gooserider

Gooserider

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LifeTime Supporter
Feb 25, 2009
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North Billerica, MA, USA, etc.
I posted a few days back about how I'd just done a total rebuild on our Polaris 380, and that it seemed to be working great. Turned out that I'm still having a problem that is leaving me a bit puzzled. :? Frequently when I go out to check the pool, the Polaris seems to be stuck and not moving other than when the back-up unit does it's cycle.

If I fish it out (after turning off the pumps, I find the wheels don't want to turn, but if I apply just a little force, the wheels break loose and start turning freely again. If I put the unit back in the pool, and turn the pumps back on, it again seems to be working fine.

Earlier this week, I opened the cleaner back up, and found a fairly large amount of coarse sand in the inner body of the unit. It looks to me like the sand may be getting into the gears occasionally and providing just enough of a jamming force to stop the unit. Does this sound like it is the problem? When there is nothing in the gears it feels nice and smooth when I turn the wheels by hand, or manually spin the turbine wheel.

The big question I have though is where is the sand coming from? The water supply to the unit is coming from the booster pump, which is feeding from the output side of our DE filter. There is no sign of DE in the pool, like there has been when I had a hole in the filter at other times. In addition, as far as I know the little stainless filter in the wall fitting is there, and in good shape. (I can't currently double check this as I can't reach the fitting from my chair...) The pool water that is going through the vacuum never touches the inside of the unit, only the water coming from the pump via the "water management system".

Leaves me with the two questions, of where is the sand coming from / how is it getting into the unit :?: And how do I stop it from getting into the gears :?:

Thanks,
Gooserider
 
Any chance that the problem is actually leakage at the pressure relief valve? Recent discussions on forum reminded me that as our valve was slowly failing, more and more water exited the valve, starving the Polaris, which got slower until valve blew completely.
 
anonapersona said:
Any chance that the problem is actually leakage at the pressure relief valve? Recent discussions on forum reminded me that as our valve was slowly failing, more and more water exited the valve, starving the Polaris, which got slower until valve blew completely.
Click to expand...

I don't think so. I haven't actually done the timing test on it, but when working it moves at a pretty good clip, and all appears normal. It is also possible to turn the wheels by hand in either direction (when both pumps are off) and you can hear and feel the gears working inside the unit, as expected.

When it gets stuck, there is definitely something jamming the gears, as it is not possible to turn the wheels in the forward direction, at least not without excessive force, though it is possible to turn them backwards. If lucky, the sand that is is jamming things up will fall out, and the bot will behave properly again. If not lucky, I have to take the top cover and the turbine cover off, and physically remove the grain of sand that is caught in the gears. It seems the plastic that they make the gears out of is just soft enough for the sand grain to jam in the valleys between the teeth and stick. This makes a "bump" that the gears can't get past, at least not with the relatively low torque that the turbine wheel provides. (And it wouldn't be all that good if the gears could roll over the bump as that would cause some pretty rapid wear...)

It isn't terribly difficult to fix this, but it is time consuming, and means I have to dig out the tools (Phillips screw driver, small pointy thing, and needle nose pliers) and partially dismantle the bot - pull it out of the pool (non trivial to do from the chair) remove the bag and float, take the screws out that hold the rear jet and part of the cover, take the rest of the cover off, then remove the screw that holds the turbine cover, and turn the gears until the offending sand grain is located, and pop it out with the small pointy thing. Then I wash as much of the sand out of the unit as I can, which is messy and tends to get water on the chair. After that I have to reassemble, which is a minor headache as the turbine cover screw is hard to get into it's hole (the pliers help) and the jet screws are also hard to get started into their inserts as the fitting doesn't like lining up with the holes... I'd estimate 15-20 minutes per jam, which happens every 2-3 days... :grrrr:

Gooserider
 
Not sure if this is your answer, but I talked to a lady yesterday who has a waterfall on the edge of her pool. She said the rocks used to build the waterfall are eroding and of course, the sand is going into the pool. It stopped up her 480 wheel bearings even though she has the inline filter in place. The sand in the bearings is very fine and apparently passes through the filters. Rocks must be sandstone...
 
Good thought, but not in this case... I have no waterfall or other such things, just the basic skimmer and returns setup. The coping around the edge of the pool is concrete, but I'm not seeing any visible signs of erosion there, so I really don't know where the sand is coming from other than just natural sources. I don't know how the sand would be making it through the main DE pool filter either - it's certainly larger than what the filter is supposed to stop!

It's still happening as a problem fairly regularly.

Gooserider

toyguy5538 said:
Not sure if this is your answer, but I talked to a lady yesterday who has a waterfall on the edge of her pool. She said the rocks used to build the waterfall are eroding and of course, the sand is going into the pool. It stopped up her 480 wheel bearings even though she has the inline filter in place. The sand in the bearings is very fine and apparently passes through the filters. Rocks must be sandstone...
Click to expand...
 
thepoolmedic said:
Are you missing the upper turbine cover? You should have to take this cover off to gain access to the turbine. This cover should protect the gears from getting jammed.
Click to expand...

No, the turbine cover is there, and has to be removed every time the Polaris gets jammed - Minorly a bit of extra nuisance both because of the added disassembly, and because the screw is in a bit of a tight corner, so I find that I have to get a pair of needlenose pliers to hold it in place while putting the thing back together. (The stainless steel screws used aren't magnetic, so they won't stick to my magnetic tipped screwdriver :( )

As best I can tell there are three possible ways the sand could be getting into the gears, but none of them seem very likely...

1. Coming in through the jet in the "water management system" that drives the turbine. Seems unlikely as the sand would have had to make it through the main pool filter, the screen in the feed line fitting, and through the jets - the particles I've found seem to large to go through the jets, and I haven't had any problems with them clogging.

2. Getting into the robot some how, and then falling into the gears when the robot goes sideways or even momentarily upside down while crawling on the walls... Again seems unlikely, as the water feed to the turbine should be flushing the gearbox out, except possibly when the backup unit diverts the water from the unit to drive it's jet. (I notice that the wheels stop turning when the backup jet kicks in...)

3. Getting in through one of the openings where the axles come out, especially the one that is on the single wheel side, since that is directly connected to the gearbox... Again except when reversing, those openings are the only vents for the turbine drive jet, so I'd expect there to be a fairly strong water flow out those holes...

Gooserider
 
There is only one way sand can get in the Polaris guts and that's via the feed hose. If it got past the finger screen, its too fine for that.

How it got past the pool filter is the real question. Time to tear it down and inspect the grids, manifold, and o-rings. Check the MPV too.

Scott
 
Will need to get a new seal O-ring before we do that, as the one we have is stretched to the point where it was a real battle to get it scrunched down enough to get the band on it, and seal the thing up at opening... I don't think there are any holes in the filter, as when I've had tears in the past, I've had DE showing up in the pool water, which isn't happening now.

The only thing that is a bit strange, is that shortly after opening, the filter started to get stopped up, like it usually does a few times when I open. (Typically I have to backwash several times during the first week after opening, and then stay at the same level for the rest of the summer...) However I turned the pump off for a couple of minutes, and then turned it back on as a temporary thing, and the pressure dropped to "normal" levels and has stayed low since....

The filter is a real old unit that isn't made any more, and is a bit of a bear to get parts for. It is on our list of things to be swapped out, but it may be a while as we have a lot of other large expenses that have higher priority - mostly revolving around how to make the house accessible...

Gooserider
 

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No push pull, no MPV... I have a skimmer that feeds the pump, which goes into the filter, then comes out of the filter and splits to feed the Polaris booster pump on one branch and the three return "eyeballs" (plumbed in series) on the other. There is a rotary valve in the bottom of the filter that switches from normal mode to backwash mode - it is tight enough that I have to put a cheater pipe on it in order to change it's position.... As I've said, it's a pretty old and obsolete system, but we have higher priorities on things that need fixing...

Gooserider
 
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