Switching Pump from Low to High produces dirt from the return!

[JesseWV]

This morning I switched the pump from Low to High to do some vacuuming. To my horror a brown jet of dirty water came spewing out of the return into my otherwise crystal clear pool! The pump had been running on low for over 24 hours due to sub-freezing over night temperatures.

I have a Hayward Vari-Flo multi-port valve on a S160T sand filter. Several years ago I did a repair to the top of the Underdrain Pipe which appears intact. I did notice that where the Underdrain Pipe slides into the diffuser there is a channel where it looks like an O-ring would go but I haven't found any mention of this O-ring in forums, diagrams of the multi-port, or rebuild kits for the valve.

For the time being I can backwash & rinse before switching to the pump back to High, but would like to know what's going on here.

1. What could be causing the dirt to enter the pool when switching from Low to High?
3. Is there supposed to be an O-ring where the Underdrain Pipe slides into the diffuser?

 

[duraleigh]

For the time being I can backwash & rinse before switching to the pump back to High

Does that solve the issue?

 

[JesseWV]

Does that solve the issue?

Yes, but only temporarily. I would prefer not to have to backwash every time I want to change pump speeds.

 

[RussH]

How long have you had the current setup and is this a new occurance? Mainly, my question is does it have a decently long history of not doing this when you switch to high?

If so, then something must be getting unseated in the valve when you switch to the higher pressure/flow of high speed. It must let at least part of the flow entrain dirt trapped on top of the filter bed and then it goes through the return to the pool. Does the valve feel like it seats firmly?

Could it be fine dirt particles that low speed wont push through the filter, but high speed is able to push through it? It seems like that would be a slower process and not result in a rush of dirt, if even possible.


Russ

 

[duraleigh]

That's a tough one. I cannot think of an obvious scenario to make that occur.

 

[JesseWV]

I've had the current filter set up for 4 years, aside from adding a new pump motor and SWG. This year at opening I did the following to the filter:

Removed the multi-port valve.
Rinsed existing sand with a hose.
Added new sand to bring to the proper level. (I seem to lose about a half inch of sand per year)
Added 2oz Bleach to sand and filled filter with water (it had a funky smell!)
Re-seated and sealed multi-port valve.
Allowed to sit for 1 hour.
Backwashed & Rinsed

I feel silly but I just found a post I made from a couple years ago about the very same thing. I guess I'm getting old.

Old Thread:
40739-Dirt-from-return-when-switching-pump-from-low-to-high

Anyhow, it seems to happen at opening when there's a lot of fine dirt and/or dead algae that needs filtered out. My main concern is that my filter is not operating properly. I am also suspect because I do see a bit of DE entering the pool if I pour it too fast into the skimmer when it is added to the filter to get that extra sparkle. There was no DE in the filter at the time when the dirt incident occurred.

After the pool is open and the water has been crystal clear for either this doesn't happen or isn't as obvious.

A question I would like an answer to is whether or not the Hayward Vari-Flo valve is supposed to have an O-ring where the Underdrain Pipe slides into the diffuser?

How long have you had the current setup and is this a new occurance? Mainly, my question is does it have a decently long history of not doing this when you switch to high?

If so, then something must be getting unseated in the valve when you switch to the higher pressure/flow of high speed. It must let at least part of the flow entrain dirt trapped on top of the filter bed and then it goes through the return to the pool. Does the valve feel like it seats firmly?

Could it be fine dirt particles that low speed wont push through the filter, but high speed is able to push through it? It seems like that would be a slower process and not result in a rush of dirt, if even possible.


Russ

 

[RussH]

I dont know about the o-ring. If you can find a parts diagram for the valve and filter combination, it should show if an o-ring is supposed to be in it. I assume you mean an o-ring between the valve and standpipe? This Pentair filter I have doesnt have one and seems to rely on a fairly snug fit between the valve and the standpipe.

Are you sure the sand is the correct type/size for the filter?


Russ

 

[JesseWV]

I am not 100% sure it's the correct sand. It was the sand that was already in the filter when it was purchased with the home.

Comparing it to the pool sand I've seen at Home Depot or Lowes, my sand is more coarse. Most of the grains are about 1 mm with sharp edges.

The filter is classified as a "high rate" filter, perhaps that has something to do with the coarser sand type?

As far as the connection to the multi-port. Yes, I'm talking about where the stand pipe slides in. The connection is snug on my set up as well. There is that indented channel inside which looks perfect for an O-ring but every diagram I've seen doesn't show inside of this area.

 

[Smykowski]

I have the 180T, and there is no oring between the multiport and standpipe.

 

[RussH]

I am not 100% sure it's the correct sand. It was the sand that was already in the filter when it was purchased with the home.

Comparing it to the pool sand I've seen at Home Depot or Lowes, my sand is more coarse. Most of the grains are about 1 mm with sharp edges.

The filter is classified as a "high rate" filter, perhaps that has something to do with the coarser sand type?

As far as the connection to the multi-port. Yes, I'm talking about where the stand pipe slides in. The connection is snug on my set up as well. There is that indented channel inside which looks perfect for an O-ring but every diagram I've seen doesn't show inside of this area.

I think high rate is a marketing term they've put on the filter. I dont know which sand Hayward specifies for their filters. If its the #20 silica sand, its supposed to be 0.45-0.55mm in size. I dont know if that could be part of the problem or not. It seems reasonable that a coarser sand wouldnt trap and hold smaller particles as well as a finer sand, but I dont know if its worth changing out the sand to find out. It would be an opportunity to inspect or replace the laterals in the filter to make sure nothing is wrong with them.

We bought our house last fall and I changed out the sand and laterals in the filter during the winter mainly to inspect and make sure everything was in order before the season started. It is ~8 years old and I had no idea what the previous owner might have done to it. The old sand was coarser than the #20 I put in it, but I dont have any reference to how the filter behaved with the old sand. I also have a one speed pump on it, although I have a 2 speed arriving today - the same one you have listed. Hopefully I wont have the same problem.

Russ

 

[duraleigh]

The filter is classified as a "high rate" filter, perhaps that has something to do with the coarser sand type?

No, that is simply marketing as rushH suggests. I am still pondering your issue and still clueless.

 

[eaamon]

new to my pool last year on a house just bought. I had a fine cloud of silt blow out of my filter every
morning when the pump turned on with my timer. after weeks of vacuuming the bottom and still getting
the silt blow out. I let accumulate for a week. then I just set the valve control to waste and vacuumed it out.
98% of it went away. now when I back flush, I rinse longer too.
hope that helps...

 

[mas985]

This is just speculation but a sand filter only filters out particles that are larger than about 20-40 microns depending on the sand and the flow rate through the filter. On low speed, the filter will tend do a little better with the smaller particles sizes than at higher speeds because the flow rate is not sufficient to force them through. However, when speed is increased, the flow rate is sufficient to force these particles through the filter.

To see if this is the case, add a little DE to the filter which should improve the filtering on both high and low speeds. Hopefully, it will also prevent the dirt from being flushed out when switching to high speed.

BTW, do you have any fine dirt/silt that is in the area or perhaps a fine pollen that can make it's way into the pool?

The other thought is channeling in the filter. This can also have the same symptoms.

 

[JesseWV]

There IS a generous amount of pollen floating around right now, but this was dirt. It's has since collected into very dark brown patches in the recessed imperfections of the liner.

I added DE to the filter and vacuumed it all up today. I got about half of the pool vacuumed when the pressure went up too high and I wasn't getting enough suction. I backwashed, added more DE and finished. I'm going to let the pump run all night on low and hopefully it won't redeposit and I can backwash it in the morning.

Again, it's worth noting that when adding DE I can see it returning to the pool if I add more than a teaspoon at a time to the skimmer. This seems abnormal to me, shouldn't I at least be able to add 1/4 cup at a time without it getting through the filter? This makes me think something isn't quite right.

I would hope I don't have channeling already since I just cleaned the sand with a hose at opening. Also, I inspected and actually measured some of the sand and the bigger grains are actually closer 0.6mm so it's probably the right stuff.