Need drain/refill recommendations

[kcbaltz]

My IG plaster pool has CYA at around 80-90 and CH above 400. I'm thinking it needs to be partially drained and I'm wondering how best to do it. Being October here in Northern California (Dixon), it's staying cool enough that I'm assuming the plaster isn't in as much danger, but it already has had some problems with thin layers popping off in places so I don't want to exacerbate that. I'm also not sure what the groundwater level is here although since we're only 60 feet above sea level and there's a lot of farming around here, I'm guessing it's not terribly far down.

In fact, I'm wondering if I should take the opportunity while it's drained to repair the plaster that's thus exposed or if I should wait for the summer and do it with the underwater hot plaster. I've done that before on a top step that I could work on without submerging my head, but I'm not sure how well I could do the lower steps.

Is there a guide to draining and refilling including how to actually pump it out?

 

[linen]

How does your water look?
Do you close your pool for the winter?

Posting pictures of the plaster trouble may help folks understand what your issues are.

 

[kcbaltz]

The water looks good, clear and blue, although I feel like I have trouble keeping it chlorinated. I'm pretty sure I need to SLAM it but I've been holding off until the draining, figuring it'd be a waste of time and money otherwise. I've also had some issues with black algae and at least one set of cracks (about 2-3 inches) in the plaster has some black algae in it. If I can't kill that with brushing and chlorine, I'm figuring I may need to chip that plaster a bit and then patch it as well.

I don't usually do much for the winter other than keep leaves out of it. I don't have any cover appropriate for winter and it's always cold enough to keep algae from growing.

I'll followup with the pictures.

 

[linen]

The water looks good, clear and blue, although I feel like I have trouble keeping it chlorinated.

If it seems to be using a lot of chlorine, do an Overnight Chlorine Loss test (OCLT) to see if you have something consuming it. See: http://www.troublefreepool.com/pool-school/overnight_fc_test I would raise your FC up to 12 ppm to do the test.

As for the drain/refill, if you pass the OCLT, you may just want to wait until spring to do the drain/refill and see what your cya is then.

 

[kcbaltz]

I didn't think CYA was likely to go down on its own. Will Spring be as good a time to drain as Fall?

 

[linen]

I didn't think CYA was likely to go down on its own. Will Spring be as good a time to drain as Fall?

It's not likely, but does happen to some people. Draining should be fine spring or fall unless you have a high water table that is seasonable. It really is up to you...but I would do the OCLT and see where that is at first before deciding.

 

[kcbaltz]

Here are the pictures. One shows the thin plaster popping happening on a step. The other shows a wall with cracks that appear to have black algae in them.

 

[kcbaltz]

OK, I'll try the OCLT and report back. Thanks!

 

[kcbaltz]

Alright, I did the OCLT two nights ago and it dropped from 15.5 ppm to 10.5 ppm overnight (8pm - 7 am). 5 ppm OCL seems pretty high, so I'm guessing I need to SLAM it until it goes down? Is that correct? The pool looks pretty clean, the filter pressure is low (near where it it after a cleaning). I'm pretty sure there's still algae in the pool, so should I get an algicide as well or will high chlorine be sufficient?

 

[linen]

Yes, you need to do the SLAM process, but first I would lower your cya level down to ~50 ppm.

 

[jblizzle]

Algaecide is more of a preventative ... although we generally do not recommend its use as it is just not needed in a properly chlorinated pool. And chlorine is all you need to eradicate the algae as well.

You just need to follow the SLAM process. [slam:9p7q7toe][/slam:9p7q7toe]

 

[kcbaltz]

If I need to lower the CYA, that means draining and refilling, the original topic of this post. Do you now feel I shouldn't wait until Spring to do that?

 

[jblizzle]

You need to SLAM the pool (whether now or in the spring), before you do that you need to get the CYA lower (either now or in the spring)

If you are going to close soon anyway, then just deal with the high CYA and the high chlorine loss in the spring.

 

[kcbaltz]

Resurrecting this thread now that it's Spring. I rechecked my CYA and it's 70-80ppm. Should I drain and refill and if so, how much? And is there danger from the plaster drying out if it gets hot?

 

[pwrstrk]

Pool math will tell you how much to drain to get to the CYA level you want to be at. I would think your plaster will be just fine.
Do you have to SLAM the pool ?

 

[kcbaltz]

I expect I will need to SLAM it as I have not been putting much chlorine in over the winter and it was in need of a SLAM before that. However, someone had recommended I wait on the SLAM until the CYA was lower, to make the SLAM easier to do.

 

[jblizzle]

Yup. You should replace ~50% of the water and then SLAM it. It is not good for the plaster to be exposed for long. If you are able to drain quickly, you may be able to mostly fill it overnight. Or drain slowly with a siphon (if possible) refill at the same time on the opposite end.

 

[kcbaltz]

Pool math says to drop 38% of the water to get down to 50 ppm.

Is the siphon method reliable? I assume I'd have to turn off the pool pump and measure progress by infrequent CYA measurements?

If I use a sump pump to drain it, it appears I could do it in a few hours with a 53 gpm pump. However, I'm guessing I can't replace the water that fast. Do people usually just use a garden hose or two? Is there a better way?

 

[jblizzle]

Well, 50ppm puts you right at the upper limit again, thus my recommendation for replacing more.

What do you mean reliable? As long as gravity continues to exist, the siphon will work down to the level of the end of the hose. Problem is you need to be able to get the dry end of the hose below the water level. You would have to have the pump off and just try to be filling and draining at the same rate. And estimate how long you need to do it based on the rate you are replacing water.

If you do not have ground water to worry about. It is certainly easier to just pump the water out and refill using a few garden hoses.

 

[kcbaltz]

I see what you're saying about 50ppm being upper limit. I'll re-read how to pick the target concentratoin and adjust this plan accordingly.

As to the reliability of the siphon method, I guess I may have meant "efficient". I.e. if I siphon of 5,000 gallons while replacing that water at the same rate, will it lower the CYA as much as draining and then replacing 5,000? Or will the incoming water dilute the CYA and thus require more siphoning? I like the siphon idea because it feels safer for my plaster and less of a time-sensitive operation. But if I'm going to have to drain 10,000 to get the effect of draining 5,000, that's less enticing.