Possible blockage.

[Iam1964]

Hi guys,

I am a new pool owner with a problem. My pool was fill about 2 weeks ago and has been running flawlessly until about 3 days ago when I noticed the pressure on my filter jumped from 20 psi to 36 psi.

I checked the filter and it was a little dirty but not excessive in my opinion. I sprayed the cartridges down and put it back together.

When I started the pump the pressure was again at 20 psi but slowly rose to 36 psi again.

i am not sure if this is significant but I “think” this problem only happened after heating the pool overnight.

There is also very very little flow from the return jets

My pool builder has been great but is on vacation right now so cannot really help.

Are there any simple checks that I can do or am I missing something completely?

Thanks.

 

[zea3]

Hi, welcome to TFP! How does your water look? Do you have a current set of test results?

 

[Texas Splash]

Welcome to TFP! What you are describing is consistent with a potential algae bloom in its early stages. Along with Zea3's questions, what test kit are you using?

 

[Iam1964]

Hi, the water looks very clear but i did throw 1lb of shock into the pool yesterday under the advise from the pool builder as the the chlorine test showed 0 chlorine (the test sample was totally clear with no color change). I am sure there was no chlorine due to the fact that I have an in-line chlorinater and there is very little flow.

 

[zea3]

You are probably seeing a nascent algae bloom. A one time application of granulated chlorine in a 17k pool is not going to fix the problem. We can teach you how to use the TFP method to take care of your pool and get rid of your algae problem if you are interested. The TFP method requires that you use an FAS/DPD test kit so you will have accurate test results so you will know how much chlorine to use in your pool. If you would like to learn more read What is TFPC? - Trouble Free Pool Simply put TFP method is to only use the chemicals your pool needs to be clean and safe. Most of the chemicals we use are available at your local grocery store. We use very few pool store chemicals, as many of them create as many problems as they solve.
We will be happy to lead you through the process if you would like to give TFP method a try.

 

[Iam1964]

Thanks for taking the time to help Zea3. The pool is super clear with no sign of algae. I think my problem is more of a mechanical problem.

This Is my first time posting here so I may have posted this in the wrong forum. I just noticed this forum is for “water chemistry”. ?

 

[ajw22]

Thanks for taking the time to help Zea3. The pool is super clear with no sign of algae. I think my problem is more of a mechanical problem.

This Is my first time posting here so I may have posted this in the wrong forum. I just noticed this forum is for “water chemistry”. ?

What size is your filter?

Having the filter pressure drop to 20 after cleaning and then rise again indicates it is not a mechanical problem. Cleaning the filter would not make a mechanical problem change.

Having your FC drop to 0 lets algae take hold in a day. Algae can be clogging your filter before you can see it in your water.

I think you subconsciously picked the correct forum section for your problem.

 

[Texas Splash]

I think my problem is more of a mechanical problem.

I may sound like the spoiler here, but I doubt it's mechanical. If you had a blockage, the PSI wouldn't change just because you cleaned the cartridges. When you rinse the carts, you remove particulates like algae that in many cases we cannot see with the naked eye until they bloom into clouds of green. What's helping you right now is the chilly water (probably about 60 degrees). If this was summer you'd probably have a soupy mess since you have had next to no chlorine in the water. Your CYA level is also in doubt which if low, results in free chlorine disappearing extremely fast.

But we hate to guess at TFP which is why the proper test kit is so important. Your builder may have left you with a simple kit, or worse yet strips, both of which won't help you much. What you need is a TF-100 or Taylor K-2006C. I recommend the TF-100 with magnetic speedstir. When you get one of those, post ALL of your test results as follows:

FC
CC
CYA
PH
TA
CH

From there we can really give you pinpoint advice to assist. As for the thread, I'll see if it needs to be moved to a better sub-forum. But keep posting here for your concerns and we'll help.

 

[Iam1964]

Thanks Texas splash,

the pool builder did leave a simple kit, pentair brand I think.

So.... I just tested the water and the chlorine level is higher than 3 and the ph is about 7.8 I think. I’m not sure how people post numbers higher than 3 as my test kit has a maximum of 3!!! Btw, I have not went through pool school yet so I really have no idea what I’m talking about ??

I have now rinsed the filter cartridges twice now and drained the filter completely.

I also noticed the flap on the back flow preventer between the chlorinator and the heater hardly moves when I turn on the pump. Previously this flap was in the fully open position.

 

[Texas Splash]

I’m not sure how people post numbers higher than 3 as my test kit has a maximum of 3!!!

Yeah, that's one of the shortfalls of those cheaper kits. The TF-100 or Taylor K-2006C come with a powder/drop solution that can test FC much, much higher with excellent accuracy. That's a big reason we recommend one of those. Also see: Test Kits Compared

The backflow thing you mention sounds like a check valve. Probably looks something like this:


It should fall shut/closed when the pump is off to prevent high chlorine levels from going backwards into the heater. We can explore that a bit more later if needed.

 

[zea3]

@Iam1964, We have had a warm winter so far, and if you are keeping the water heated algae can take hold very easily. Algae loves warm, under-chlorinated water. The pool will slowly become cloudy and eventually turn green if the algae is not killed. The filter is clogging because it is doing its job, catching very tiny particles of stuff in the water and holding on to them until you clean the filter. The chlorine you use in the chlorinator may give enough chlorine at this time to keep the algae knocked back so the water is still transparent, but soon it will not be able to kill the algae fast enough to prevent the pool from turning green.

An important number we need to help you is the CYA level (cyanuric acid). This is the chlorine stabilizer that is part of every dichlor/trichlor pool product and is commonly found in bags of "shock" or chlorinating tablets. When the CYA level rises too high, the regular dose of chlorine becomes ineffective. You have to maintain a CYA to chlorine ratio to keep the pool clear and properly chlorinated. A pool store may say you have "chlorine lock". That's just another way of saying the CYA is too high. Most basic test kits do not test CYA levels, but the kits we recommend do. If you have been using chlorine tablets exclusively for 2 weeks you have added approximately 2ppm of CYA per tablet used. If you used a dichlor "shock" then it added another 3.5 ppm. If your builder did not add CYA at start up you may not have enough CYA to prevent the chlorine from burning off in the sun before it kills the algae. If your builder threw in 10lbs of stabilizer then you may have too much. Both problems can lead to an algae bloom but the solutions are different. This is why we need good test results so we can tell you how to fix the problem.

 

[Iam1964]

Hi @zea3 thanks for the detailed explanation.

I am still not sure that I have clogged filters. I have removed them twice now and thoroughly cleaned them. They look like new.
Would it cause any damage or problems to remove the 4 filters completely and then turn the pump on? My thought is that if it is the filters that is the problem then the water flow should increase and the pressure will be reduced. If it is not the filters causing the low flow then that would mean the restriction to flow is somewhere is?

Is this a viable test?

I have also just ordered a complete test kit from amazon. Should be here Friday.

thanks

 

[Jimrahbe]

1964,

I don't see a problem with you running a "test" with the cartridges out... Try it and see what happens.. I suspect that the filter pressure will not go up..

You have algae, not a mechanical issue, but if running without the cartridges helps you understand the problem, go for it..

Thanks,

Jim R.

 

[zea3]

You said the pressure dropped after cleaning the cartridges and eventually rose back up. The microscopic, dead algae and other organic material oxidized by chlorine slows down the flow of water when the cartridges get full. A cartridge filter can typically remove debris as small as 10-15 microns. The average human hair has a width of 80 microns. We recommend cleaning the cartridges when you see a 20% rise from the clean pressure reading, which is about where you are seeing reduced flow. The cartridge may look a little dingy to you, but not full. We tend to think of "full" as something visibly packed with crud. A cartridge filter will have reduced flow long before it gets to that point. When cleaned, flow is restored.

Something else that may be clogging your filters is plaster dust. Freshly plastered pools shed plaster dust for the first few weeks. Have you been brushing the pool daily since it was filled? I still think the problem is algae but I want to cover everything.

 

[Iam1964]

@zea3 , I have been brushing the pool daily since it was filled. I will try hosing the filters again.
thanks

 

[ajw22]

@zea3 , I have been brushing the pool daily since it was filled. I will try hosing the filters again.
thanks

You need to do more than hose the cartridge. Read...

Cartridge Filter Use and Care - Further Reading

www.troublefreepool.com

 

[Iam1964]

Ok guys, I (you) may have solved the issue. Many thanks to @zea3 , @Texas Splash , @Jimrahbe

i did remove the cartridge’s and ran the pump. The pressure was “normal” meaning that I do not have any blockages in the pipe work.

i then gave the cartridges a thorough cleaning again and replaced. The pool is running again at a pressure of 20 psi.

I’m assuming the pool still has a lot of plaster dust that was clogging the filter so I will now check on a daily basis.

Thanks again everyone.

 

[Lilypad]

Get yourself a sweeper nozzle like the one below. Does a great job getting all the large and very small debris out of the cartridge filter pleats. Congrats on the new pool. As mentioned, get a recommended test kit and ask any questions you have along the way!

Melnor Sweeper Nozzle-4151-6 - The Home Depot

 

[Iam1964]

Thanks @Lilypad , the test kit should be here Friday.