Dirt blowing in pool on filter startup

[xenia]

Hi 2nd year pool owner. reading TFP post have helped me alot have a clean nice pool but now I need some help. I have a 27 ft round above ground pool with a hayward sand filter(this year I am running filter glass and pea gravel), water is perfect, but when I have the directional diffuser on the outlet (the part that necks down from 1.5" inch a smaller hole to increase pressure and water movement the filter blows dirt into the pool at initial startup and pool bottom shows alot of dirt. The filter did this last year as well when I had sand in the filter, After troubleshooting i found when I remove the diffuser and let 1.5" inch all the way into the pool no dirt comes out at startup but my water movement is impacted so I dont want to operate this way. Is this due to very high initial startup pressure pushing dirt all the way out of filter? It seems initial pressure is causing the problem.
What size should the outlet hole be,
inital clean filter pressure is like 18 PSI with the diffuser and about 10 PSI without. So this extra 8 PSI seeems to blow dirt back into the pool at startup.


any help is appreciated!

 

[jblizzle]

Welcome to TFP!!!

If anything, putting the smaller jet would reduce the flow rate through the filter (and raise the pressure). So I do not see off-hand how lowering the flow rate would allow the dirt to pass through.

Do you have a multi-valve? Maybe the increased pressure is allowing water to bypass the filter through the spider gasket.
Do you have any air in the pump/filter? If the air in the filter is compressed, when the pump turns off it could push dirt backward through the filter and on start-up this dirt then sneaks by the filter through the valve.

Kind of guessing here

 

[xenia]

yes I have a hayward multivalve, I agree with the reducer less water is flowing thru the filter but it blowing dirt as I say. The "eyeball" jet had a 3/4 in hole in it. So it reduced from 1.5" to 3/4" is that a standard size outlet hole? I thinkign mayeb a 1" hole will be less pressure but that may be bandading the problem.

today I did this I turned the filter on with 1.5 inch direct to the pool and no dirt as normal pool is prefectly clean, then I connected the 3/4" eyeball with the pump on (to test non start up condition but to increase pressure of the system ) after a bit I see some dirt in the bottom of the pool! Your comment of the gasket is making sense now.Normally more pressure will cause stuff to fail, the hayward is brand new last year but it seems more pressure is causing the bypass you mention or pulign dirt of the top of the filter bed back into the pool.

Is there a way to test the multivalve or this spider gasket to see if it is okay?

 

[jblizzle]

Best I can think to suggest is just opening up the multivalve and inspecting the gasket and spring to be sure they are seated properly.

 

[duraleigh]

Another way to look at that issue might be to figure out why dirt is getting into th4e return line regardless.....it shouldn't be.

How often do you backwash? Do you rinse after you backwash? Can you open the filter and inspect the bed?

 

[big-e]

Just curious if you have been able to resolve your issue? I am on my 4th season on my above ground pool and am having the same issue. in addition, it returns dirt while vacuuming. I know its doing something because if it wasnt filtering at least some, then why would it be able to shoot dirt out upon startup? Ive never thought about the diffuser, I have an aqualuminator light w/ diffuser for the return. Ive looked inside the multiport once before but things looked ok to me, Im thinking about going to get a new spider gasket tomorrow and put it in to see if I have any luck. All I know is I have gone from having a crystal clear pool my first couple seasons, to having a pond in my back yard and I cant take it anymore. Thanks for the help!

 

[asxetos]

The reduction / restriction of output pipe diameter can create a higher pressure spike during the initial fluidization of the sand bed inside the filter. During this initial phase, direct paths can be created through the sand bed, allowing dirt to reach the output of the filter.

Once the sand bed is fully fluidized, direct paths through the bed are eliminated.


Some sort of "soft-start" circuit could be used to reduce the initial pressure spike at startup, although this might not be an economical solution.

 

[Noni]

Are you rinsing after backwashing? Normal filter start up should not put dirt, sand in your pool but if you backwash & go straight to filtering without rinsing first it will every time.