Contemplating a UV system

Ian196499

Gold Supporter
Silver Supporter
Aug 12, 2018
77
England
Hi

I am contemplating fitting a UV system to help with a build up of CC which I experienced last season.
we live in the north of England where temperatures don’t get too high and the pool season lasts for 6 months. To make the pool more usual we had an enclosure fitted 2 years ago which is a great addition.
The enclosure has a polycarbonate roof with UV filter and glass walls. The central section of the enclosure does slide back so the pool theoretically gets some UV exposure but to be honest the weather is rarely good enough for that in England. Hence the CC problem due to low UV exposure.
last season I ended up having to SLAM the pool a couple of times but then have the problem that it took an age to get the FC levels back down to normal for the same reasons.
So I’m now thinking of fitting a UV system to break down the CC and running with a lower FC level.
My latest test results are
FC 4.2
CC 0.2
Ph 7.5
TA 160
CH 275
CYA 25
Temp 27c
Thanks for any thoughts / pros / cons

cheers
Ian
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
15,828
Northern NJ

A CC of 0.2 is not a problem if that is what you are looking to fix.

A UV system will not let you run at a lower FC level. You need to maintain your FC/CYA ratio for proper sanitation.

For CYA 30 (we round up) your FC target should be 4 - 6.
 
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Ian196499

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Aug 12, 2018
77
England

A CC of 0.2 is not a problem if that is what you are looking to fix.

A UV system will not let you run at a lower FC level. You need to maintain your FC/CYA ratio for proper sanitation.

For CYA 30 (we round up) your FC target should be 4 - 6.
Hi
Sorry I didn’t explain properly. My current levels are fine as I’ve only opened the pool two weeks ago. I’ve tried to follow the FC / CYA tables ever since I had an algae bloom due to following the pool guy’s advice (🤦🏻‍♂️).

in Reply to a previous post I was advised to have a CYA in the 20-30 range as the enclosure gives a sort of indoor pool aspect. The pool guy advised zero CYA but we suffered from the harshness of the chlorine. It’s definitely better having a CYA at 25 but it would be no problem to raise to 30.

My problem came last season after a few weeks which is that the CC level gradually builds up even when I’m following the advice as best I can. I keep the FC levels up, scrubs the pool and Hoover weekly etc.
Reading the pool school and other articles I read that the pool needs UV to breakdown the CC. Due to the enclosure I “think” my issue is that it’s not getting enough UV.
I could open the enclosure once a week ( would that be enough ?).
I have then read about UV systems and hence my question. Obviously for an open air pool this would be unnecessary as there is a big UV source in the sky.
so I was after some advice as to whether it is a sensible option for me to fit a UV system or whether just opening the pool to the air once a week would be enough?
Thanks
Ian
 

Ian196499

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Aug 12, 2018
77
England
The UV system is not your answer. Any CC result at .5 ppm or less is the same as ZERO.
Hiya - my current results are not the issue. It’s that the CC slowly builds up even though I’m following the “method”. As we have a pool enclosure cos our weather is not so great in the UK I “think” this slow build up is due to lack of UV but being a newbie I’m not sure.
Last year when it got above 1 I would slam the pool which would clear it overnight but then it takes days for the FC to reduce.
 

Ian196499

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Silver Supporter
Aug 12, 2018
77
England
Try opening the pool and letting it breathe.

What chemicals do you use in the pool? Does your pool guy put in any MPS shock?
I’ll give it a go this year before spending a few hundred on a UV system and see how it goes.
I sacked the pool guy and now do it myself following the TFP method although bleach above 3-4% is not available here reliably.
 

ajw22

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TFP Guide
Jul 21, 2013
15,828
Northern NJ
Last year when it got above 1 I would slam the pool which would clear it overnight but then it takes days for the FC to reduce.
That indicates an algae problem not a UV problem. If the CC accumulation was from lack of UV the SLAM Process would not clear it.

Looking at your PoolMath logs you rarely had high CC in the last 2 years and when you did you were keeping your FC too low. .
 
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Ian196499

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Aug 12, 2018
77
England
That indicates an algae problem not a UV problem. If the CC accumulation was from lack of UV the SLAM Process would not clear it.

Looking at your PoolMath logs you rarely had high CC in the last 2 years and when you did you were keeping your FC too low. .
Thanks - I must confess to being poor at logging my test results. This season can be my challenge to do it better!
I’ll take your advice and just open the pool more this year and see how that goes.
 

PoolGate

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TFP Guide
Jun 7, 2017
4,483
Damascus, MD
Send me the money instead. I will do a seance every time you think your CCs are too high. My method will be at least as effective as the UV system.
 

Ian196499

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Silver Supporter
Aug 12, 2018
77
England
😂😂😂😂 that made me laugh!
But too late, AJ talked me out of it!
I actually started down this thought path because I read the following in a TFP article on sanitisation:- “UV might be of some value in an indoor pool in conjunction with chlorine to help destroy persistent chloramines. “
given our enclosure makes it a bit like an indoor pool ( partially) I thought it might be useful.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
16,574
Tucson, AZ
Guys, seriously, knock it off with the “UV is voodoo” nonsense. The OP has a very specific issue caused by lack of sunlight. If you ever visited England you would know that it isn’t the best place to get a tan. The weather in the height of summer there is mild by comparison in the USA where most pool owners have their pools. UV does help breakdown CC’s, that is a simple fact of chemistry. In an indoor pool, which is effectively what the OP has, one can very easily build up CCs over time EVEN WHEN the FC/CYA ratio is adhered to.

The OP has a choice in his scenario - either run the pool at the higher end of the FC/CYA ratio and shock the pool as-needed to bring CC levels down OR instal a UV system to help breakdown organics and bather waste IN CONJUNCTION WITH CHLORINE to help reduce the CC load.

If the OP chooses to install UV, then you want to get the largest system you can afford and plumb it in a parallel loop configuration. You want to run the water through the parallel loop as slow as possible but high enough to satisfy any pressure switch that controls the UV source. UV photolysis requires both high enough fluence, or dose, and long contact times. Most modern UV systems are capable of being controlled by automation to allow you to specifically treat the water at the right times and then shut off the system when not needed. Doing it right is a big expense so you want to exhaust all other simpler methods first so that you don’t waste money unnecessarily.
 
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Ian196499

Gold Supporter
Silver Supporter
Aug 12, 2018
77
England
Guys, seriously, knock it off with the “UV is voodoo” nonsense. The OP has a very specific issue caused by lack of sunlight. If you ever visited England you would know that it isn’t the best place to get a tan. The weather in the height of summer there is mild by comparison in the USA where most pool owners have their pools. UV does help breakdown CC’s, that is a simple fact of chemistry. In an indoor pool, which is effectively what the OP has, one can very easily build up CCs over time EVEN WHEN the FC/CYA ratio is adhered to.

The OP has a choice in his scenario - either run the pool at the higher end of the FC/CYA ratio and shock the pool as-needed to bring CC levels down OR instal a UV system to help breakdown organics and bather waste IN CONJUNCTION WITH CHLORINE to help reduce the CC load.

If the OP chooses to install UV, then you want to get the largest system you can afford and plumb it in a parallel loop configuration. You want to run the water through the parallel loop as slow as possible but high enough to satisfy any pressure switch that controls the UV source. UV photolysis requires both high enough fluence, or dose, and long contact times. Most modern UV systems are capable of being controlled by automation to allow you to specifically treat the water at the right times and then shut off the system when not needed. Doing it right is a big expense so you want to exhaust all other simpler methods first so that you don’t waste money unnecessarily.
Hi , thanks for the detail. You’re definitely right about the weather in the UK!
that was the main driver for buying the enclosure in the first place as it allows us to use the pool even on a cloudy / rainy day, of which there are many in the Uk 😊
As AJW suggested, I’m going to give it a go of being more rigorous with my testing and giving the pool an airing once a week even if we have no sun just to see if that works.
If not then I’ll pursue this further. I’d like to do the work myself as I have done some parts of the plumbing myself.
however I’m no expert so i didn’t understand what you meant by “plumb it in a parallel loop configuration.” Can you point me in the direction of how this would work?
Part of the problem in the UK is that the industry is very small and hence it’s hard to find equipment / advice. Most of the products that are talked about here are not sensibly available in the U.K. as far as I ca n ascertain. But maybe I just don’t know where to look....
Cheers
Ian
 

Ian196499

Gold Supporter
Silver Supporter
Aug 12, 2018
77
England
Hi , thanks for the detail. You’re definitely right about the weather in the UK!
that was the main driver for buying the enclosure in the first place as it allows us to use the pool even on a cloudy / rainy day, of which there are many in the Uk 😊
As AJW suggested, I’m going to give it a go of being more rigorous with my testing and giving the pool an airing once a week even if we have no sun just to see if that works.
If not then I’ll pursue this further. I’d like to do the work myself as I have done some parts of the plumbing myself.
however I’m no expert so i didn’t understand what you meant by “plumb it in a parallel loop configuration.” Can you point me in the direction of how this would work?
Part of the problem in the UK is that the industry is very small and hence it’s hard to find equipment / advice. Most of the products that are talked about here are not sensibly available in the U.K. as far as I ca n ascertain. But maybe I just don’t know where to look....
Cheers
Ian
plumb it in a parallel loop configuration - is this what I would call a by-pass where you have a flow valve at each end of a by-pass to control the flow through the pipework?
Thanks!
Ian
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
16,574
Tucson, AZ
Look at this Installation Manual for a Paramount UltraUV system -


There are multiple different plumbing configurations starting on page 7. Using the By-pass Loop configuration allows you to meter how much water the UV sterilizer is getting. This particular UV system has a pressure switch to protect it if flow stops. Pressure switches aren't the best way to ensure flow, but they are the cheapest and easiest to implement. There are also optional flow-switches that would work too.
 
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Ian196499

Gold Supporter
Silver Supporter
Aug 12, 2018
77
England
Thanks - a useful read. Looking at the sizing charts I suspect I would only need one unit based on the flow rate and the size of our pool but I’ll check that out.
It seems they don’t recommend fitting a by-pass unless the unit would need to be removed for service and it only needs a flow switch if it’s below pool level ( which it wouldn’t be)
they also make the claim that the unit would greatly reduce the need for chlorine but I understand I would still need to comply with the FC/CYA levels to avoid algae which makes sense.
They state the unit should be after the filter. I’m also thinking of fitting a SWG based on comments on the forum ( they sound great!)- if I did do that would this unit be before or after the SWG? We also have an air-source heat pump so I’m thinking the order should be :- pump - filter - UV - heat pump - SWG. Does this sound right?
Thanks again for the help!
Cheers
Ian
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
16,574
Tucson, AZ
Before the heat pump is probably best. My personal preference is for a bypass loop configuration because you don’t need to flow all of the pool water through it and the UV oxidation works best when contact times are longer. You also don’t want to run it all the time either. Flow switches are safer than pressure switches but I understand their decision to use a pressure switch.

Ozone and UV manufacturers always claim that their systems reduce the need for higher chlorine levels and, while there is some kernel of truth to it, it’s not the whole story and it’s generally safer to follow the FC/CYA ratio that TFP suggests.
 
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