2 weeks of SLAM and still green

[RobNorthey]

Hi everyone,
i'm a big fan of this forum and appreciate any advice and support for my problem
5th year with an ingorund vinyl pool. Didn't open the pool last summer. This year, it's been opened for 2 weeks. I started SLAM right away. But it's stayed green with little to no improvement. I can see the bottom of the shallow end, but not the deep end. I'm brushing and vacuuming daily. Testing and refilling chlorine 3 times a day. In the shallow end, seeing little to no debris. there are dead algae (which is vacuumed). I backwash only when the PSI's gone up 25% (normal is 15PSI)

My test results
CYA 30
FC 20

didn't test anything else. I usually don't test beyond CYA and FC and the pool's always cleared after a week of SLAM
I suspect my sand filter may not be working correctly and hence the long SLAM. The pump is likely oversized because sand comes out the backwash pipe. What can I do to confirm the sand filter is working correctly and the level of sand inside is at the right level? open to other suggestions to improve the SLAM results. If SLAM is successful, I would appreciate suggestions for right size pump. Thanks everyone!

 

[JohnT]

Welcome to TFP!

A green pool is a chemistry issue, not a filter issue, though the clarity may or may not have to do with your filter. Metal in the water or algae are the most common issues.

If algae, just a couple of days of SLAM should result in a notable change in color. Most commonly from green to a brown or grey green, then to a blue-grey color.

Have you done an over night chlorine loss test?
Overnight Chlorine Loss Test

 

[RobNorthey]

Thank you.
There's been no noticeable improvement in over a week. Pool mostly filled with rain water.
I'll try OCLT tonight and share the results. Thanks

 

[newdude]

Hey RN and Welcome !!!

Carry on until you get a couple days off, say, this weekend. And plan on being home. You need 2 hour tests/doses at first when it's bad, or it's going to take forever. It still works, but slow.

When the FC mostly holds 2 hours, go to 3, then 4 and so on. Day one you can get small errands done between doses, such as mowing the lawn, or dropping a kid somewhere. Day 2 will hold twice as long, getting 4 or so hours between doses and that will free you up for longer errands like watching the kids soccer game, instead of just dropping them off. By day 3 of frequent dosing, the FC usually holds long enough to get back to work (Monday).

Go right until bed. You only battle the alage once the sun is low/down, and can make up serious ground.

You can dose early at any time to buy yourself the next X hours away. Hit it as soon as you return.

Brush and vac at least once daily.

You got this.

 

[RobNorthey]

Thanks for the encouragement Newdude!
I'll step up the frequency. It's back to the basics for me

 

[RobNorthey]

FYI, didn't pass OCLT. Lost 1.5 FC and 1 CC. Thanks

 

[newdude]

Full SLAM ahead.

 

[wireform]

Don't test for the CC until your chlorine holds and the water clears up as it's just wasteful and doesn't change any part of the process.

 

[newdude]

+1, any fail is a fail. You don't need to fail 2 of the 3, and the OCLT isn't even needed until there is crazy clear water with no poofing or otherwise visible algae.

 

[RobNorthey]

Thanks everyone. I'm continuing with SLAM
I'm also having problem with sand coming out the waste pipe during backwash. From reading this great forum, my pump is oversized (I just replaced the spider gasket and have no sand coming out the jets so ruling out those factors). My filter max flow rate is 60GPM. Any recommendations of appropriate pump size? thanks

 

[duraleigh]

Yeah, your filter is a little undersized for the size of your pool. The 1 hp pump matches the filter pretty well. Are you thinking of changing anything?

 

[RobNorthey]

Funny. I had thought the filter was ok and I wanted to downsize the pump or look at VS. My goal is to not loose sand when backwashing. I welcome any advice and reommendations of equipment changes if necessary. I'll read up on filter sizing. Thanks

 

[duraleigh]

Losing a little sand (maybe like a teaspoon or so is normal. How much are you loosing each backwash?

 

[RobNorthey]

definitely more than a teaspoon. I say a small handful. It leaves a clear ring by the curb.

 

[duraleigh]

I am above my pay grade on this but I think it may be worthwhile to open up and inspect the multiport valve. There is a "wagon wheel" gasket inside that may not be seating properly and allowing the sand to leak around it.

I would suggest you wait until someone else confirms that can be a problem. I have never experienced it but seem to remember that as a possibility
@1poolman1 may have some advice on that

 

[RobNorthey]

Thanks Duraleigh! I may have read that thread. I did replace the spider gasket. But thanks to you, I also learned it's ok to loose a little bit of sand. After I finished SLAM, I may look at changing up my pump.
If I backwash with a VS pump, can I run it at a lower RPM? I'm thinking at max RPM, the flow rate is exceeding the filter's limit and hence the slightly more than usual sand discharge. If others with VS pump and sand filter setups can share your experienc.e Thanks

 

[1poolman1]

Thanks Duraleigh! I may have read that thread. I did replace the spider gasket. But thanks to you, I also learned it's ok to loose a little bit of sand. After I finished SLAM, I may look at changing up my pump.
If I backwash with a VS pump, can I run it at a lower RPM? I'm thinking at max RPM, the flow rate is exceeding the filter's limit and hence the slightly more than usual sand discharge. If others with VS pump and sand filter setups can share your experienc.e Thanks

MPV gasket will not cause a sand leak at backwash and shouldn't during filtration either. Sand should never be able to enter the standpipe/diffuser in the filter.
Understand what happens in the filter on backwash.
The water enters the tank from the bottom (laterals) and if strong enough, liquifies the sand bed.
The dirty water then exists the MPV through the same openings that the water enters in filter mode. It then exists through the backwash port.
If the pump is, in fact, too strong, or there is too much sand in the tank, you will see sand wherever the backwash exits on the ground and it won't stop for a very long time because the sand in the turbulent water can exit through the valve. We want to "liquify" the bed, get all the grains moving, but not so strong as to push them out the valve. A small amount is normal. That's why I always recommend inspecting and, probably adding 50# to most filters after 5 years.
The pump can be undersized on sand filters that start with a 500 or 600 charge of sand. A VSP can be too powerful if run at full speed, but you can't really backwash at lower ones either, there is a balance that has to be found with each pump. Also depends on the size VSP. A 3hp may properly backwash at 2500 where a 1.5hp may not. Also, the type of pump. The Super Flo is a medium head pump, the Intelliflo a high head, for example.

 

[RobNorthey]

Thanks 1poolman1! Great explanation. When you say "500 or 600 charge of sand", is that pound of sand?
The more I read, the more I think my pump is oversized for the filter. I'll look at my equipment after my SLAM is done

Update, after 3 weeks, I can finally see the bottom of the deep end. I see the light. Thanks everyone for your help!

 

[1poolman1]

Thanks 1poolman1! Great explanation. When you say "500 or 600 charge of sand", is that pound of sand?
The more I read, the more I think my pump is oversized for the filter. I'll look at my equipment after my SLAM is done

Update, after 3 weeks, I can finally see the bottom of the deep end. I see the light. Thanks everyone for your help!

Yes, pounds. Yours should have started with 250#.

 

[RobNorthey]

ok. Thank you