Sand Filter reducing flow to the heater requiring constant back flushing

[BRENDAN M]

Hi All,

I am a long time reader, first time poster. I want to say thanks in advance to all the great advice I have gotten from TFP over the past several years.

My pool was built in 2015 and is used for only 4 months per year as the pool season is quite short in Whistler BC. From the very start I have had a problem where within a few days of a backwash I will get the LO reading on my heater. This can be remedied by a good backwash but within a few days it happens again. This is obviously very frustrating and likely not good for my equipment.

My pool is small at 14x22 and not deep, It is approx. 8,500 gallons. I have a 0.5 hp Hayward Century, I have Hayward Pro-Series High Rate Sand Filter with a 44 GPM Design Flow Rate 20 1/2 Inches. I also use a Delta UV Germicidal Lamp , I have a 250,000 BTU Hayward Propane (high altitude) heater. My pool is at 2000 ft above sea level.

After a backwash after around 1 day the Delta UV Lamp goes to Fault (this is my early warning my heater will go) with a day or two the heater flashes LO and a backwash is required to get the system working again. If I put the filter on recirculate the heater comes back to life and the UV lamp does as well. Obviously the UV needs a higher flow to work than the heater which is why it quits first.

I have opened up my sand filter and there was very little "gunk" on the top of the sand. It looked very clean. What little I took out did not improve the situation.

This is not a water issue. This has been happening since the day I got the pool (builder took off and takes no responsibility) This happens when the water is perfect and when it is not. There is no difference between when the water is perfect and when it is not. I test my water daily and keep it in balance. I know other posters have gotten the LO light due to water issues.

My question to the group is:

Is this a pump issue - Do I need a more powerful pump? Or is this a filter issue? Or is it something else?

Any and all help is appreciated.

 

[mknauss]

Welcome to the forum!
If the pump was too small, it would never work.
Do you have a full set of test results? Algae is the most likely culprit when flow rate slows over time.
Do you have filter pressure right after backwash and then when the heater pressure switch will no longer allow it to run?
I suggest you read ABC's of Pool Water Chemistry and consider reviewing the entire Pool School eBook.

 

[BRENDAN M]

Welcome to the forum!
If the pump was too small, it would never work.
Do you have a full set of test results? Algae is the most likely culprit when flow rate slows over time.
Do you have filter pressure right after backwash and then when the heater pressure switch will no longer allow it to run?
I suggest you read ABC's of Pool Water Chemistry and consider reviewing the entire Pool School eBook.

Thanks for the reply. I appreciate your suggestions but I have already read those and done a ton of trouble shooting on this.
I have asked a two pool professionals and they have no idea what is causing the problem. I am hoping someone on here can help.

As mentioned I do not believe this is not a water issue. I keep the water very well balanced with a Taylor Complete Test Kit. I take my water seriously. As mentioned, I read a thread on here where another users heater would go LO and his problem was Algae in the water so naturally I went there first. There is no change whatsoever regardless of the water.

I opened the pool this weekend and I used Liquid Algaecide first then shocked it twice before balancing. The UV failed within 24 hrs and the heater within 36. There is no way there could be Algae in the water.

"Do you have filter pressure right after backwash and then when the heater pressure switch will no longer allow it to run"

There is very little or no change in the pressure between backwashing and heater failure. Right after backwash, the UV and the Heater work fine but over the course of a few days they both stop working. Upon backwashing or switching to recirculate they work.

I forgot to add that I have 1 1/2 inch pipe and the pool equipment is at one end of the pool inside a structure so there is not a lot of distance of pipe.

 

[duraleigh]

Welcome to the forum

A filter's job is to capture debris. That is what it is doing.

As it captures debris, the pressure increases and the flow to your heater slows. When you backwash, the debris is flushed out so you turn your pump back on and the cycle starts again.......over and over.

You have a pool water chemistry problem. It is almost always algae related and you will need to rid your pool of algae and break that cycle. The SLAM is the correct way to do that but, at this point, you do not believe your chemistry is off so you must get on board with that explanation before you can solve the problem

 

[swimcmp]

You would have to ask Hayward if the pump and filter are big enough to supply the minimum flow required once the filter is starting to get dirty. I personally don't think your pump and filter are big enough

 

[YippeeSkippy]

Am I reading that your only sanitation method is a UV light? Do you also use chlorine?

To help you determine if its chemistry or equipment problems, please tell us:
FC
CC
pH
TA
CH
CYA

And does your water look gin-clear?? If it doesn't that tells us you have "something" in your water which your filter is capturing.

Maddie

 

[JamesW]

What exact pump do you have?

What is the pressure right after a backwash and what is the pressure when the heater gives a "flow" error?

How many returns do you have and what type of fitting is on the return at the pool?

If the returns have eyeballs, what is the diameter of the orifice?

How high is the heater above the surface of the water?

 

[BRENDAN M]

Hi Everyone,

I am overwhelmed with the kindness that you have shown here helping me with my problem. I will try to answer several of the above responses in one reply.

Water: The water is crystal clear. I use a combination of chlorine and UV. I believe it is impossible to have Algae in the water at this point in the season due to the temp'. I pulled the safety cover off the pool for spring start up at 5:00 pm May 17. At that point the water temp was 44 F (Nights have still be going into the 40's in Whistler right now) I fired up the pump and heater that night. It ran all night and was 75F by 9 am on the 18th. The UV light went to fault around 1 pm on the 18th and the LO light came on the heater by 4 pm that day. After starting the pump on the evening of the 17th I shocked the water twice and added algaecide. The next am I balanced the water. The start up water was very easy to balance this year.

What exact pump do you have?

Haywood Self Priming 0.5 HP Century Model S48H2N122B3

What is the pressure right after a backwash and what is the pressure when the heater gives a "flow" error?

I will need to replace the pressure gauge and get back to you on this. I notice very little change in pressure. Perhaps the gauge is faulty. The pressure has always been low since the pool was built. I feel the pool builder was not that knowledgeable but I had to take what I could get as he was the only builder who would come up from Vancouver to do it.

How many returns do you have and what type of fitting is on the return at the pool?

I have 2 returns. Eyeballs

If the returns have eyeballs, what is the diameter of the orifice?

I am unsure exactly what the diameter is. Is there a good way to measure this? The opening is roughly the size of a quarter.

How high is the heater above the surface of the water?

The heater is 9 inches above the surface of the water.


Again, thanks so much for everyone's help.

 

[JamesW]

Heaters usually have a pressure switch and not a flow switch.

You probably have just barely enough pressure after the heater to close the pressure switch when the filter is clean.

The smallest amount of anything that gets in the filter reduces the flow enough to reduce the pressure after the heater to a level that's insufficient to close the pressure switch in the heater.

You can try to replace the eyeballs with smaller diameter eyeballs to generate more back pressure.

However, this would reduce the flow and make the UV go to fault if it uses a flow switch.

You can adjust the pressure switch, but if you get the adjustment wrong, you risk causing the heater to run with no flow if you adjust it too far.

You can switch to a flow switch instead of the pressure switch.

You can increase the pump size, but it's probably not necessary.

A big cartridge filter would have been a better choice for your situation.

I would try the eyeballs first.

Maintaining the chemistry perfectly will help keep the filter clean.

Once you get a new gauge, report the pressure readings and we will see what that shows.

 

[BRENDAN M]

You would have to ask Hayward if the pump and filter are big enough to supply the minimum flow required once the filter is starting to get dirty. I personally don't think your pump and filter are big enough

Thanks for this. How do you define dirty? The pool was very clear when I fired it up. I think you are on to something as this problem has plagued the pool since day 1. I am sure it is an equipment issue. If I were to swap one thing first to try to fix the problem would you opt for a larger pump or different sand filter? If so, can you tell me what size you might choose?

 

[splashpad]

My pool is small at 14x22 and not deep, It is approx. 8,500 gallons. I have a 0.5 hp Hayward Century, I have Hayward Pro-Series High Rate Sand Filter with a 44 GPM Design Flow Rate 20 1/2 Inches. I also use a Delta UV Germicidal Lamp , I have a 250,000 BTU Hayward Propane (high altitude) heater. My pool is at 2000 ft above sea level.

Based on your pump & filter info,

Thanks for this. How do you define dirty? The pool was very clear when I fired it up. I think you are on to something as this problem has plagued the pool since day 1. I am sure it is an equipment issue. If I were to swap one thing first to try to fix the problem would you opt for a larger pump or different sand filter? If so, can you tell me what size you might choose?

You could change your pump up to a 3/4hp or 1hp (2-spd or VS) as long as the max output is not more then your filter can handle.

 

[duraleigh]

this problem has plagued the pool since day 1. I am sure it is an equipment issue.

So the flow starts adequately for you after backwash, right? Then, the flow slows. What changes about your equipment during that period and what does backwashing do to "change" your equipment.

Regardless of the size pump or filter, the system at first works and then it slows (clogs) until you backwash again. That is a chemistry issue.

Your description of the situation is like a hundred others we have seen on this forum over the years.

Always look for the simplest explanation.....it is the correct one about 95% of the time

 

[sktn77a]

If it weren't for your comment about the light, I would suspect a bad flow/pressure switch or thermal switch in the heater. Do you have any way to estimate the water flow?

 

[BRENDAN M]

So the flow starts adequately for you after backwash, right? Then, the flow slows. What changes about your equipment during that period and what does backwashing do to "change" your equipment.

Regardless of the size pump or filter, the system at first works and then it slows (clogs) until you backwash again. That is a chemistry issue.

Your description of the situation is like a hundred others we have seen on this forum over the years.

Always look for the simplest explanation.....it is the correct one about 95% of the time

Thanks but I have struggled with this issue for 3 seasons always working with the water. Nothing with the water ever changed it. This start up was done when the pool water was 44F. I believe it shows that it can't be an algae issue. It simply could not form in 24 hrs especially when I used Algaecide and shocked it twice in that period.

Yes the equipment works after a backwash but fails quickly. Is it possible that the pump is providing just enough flow to run the UV and heater when it is totally clean and the smallest amount of debris in the sand filter is causing the flow to slow slightly causing them to both to stop working?

If this were the case would it not be an undersized pump vs a water issue. All pools will get debris in the skimmers and sand filter regardless of how clean the water is.

But complicating the search for an answer is both the heater and UV work when the sand filter is set to recirculate. I assume a larger pump pushes water through the sand filter at a faster rate?

I would like add, the plumbing job was inefficient and to make it fit inside an enclosure there are lots of 90 degree turns. I am sure this is taxing the 0.5hp pump.

Thanks again for your interest in my problem.

 

[duraleigh]

Can you post current test results?

Can you see the backwash? Is it dirty?

A working psi gauge is virtually mandatory when troubleshooting your circulatory system.

The 90 degree turns are not ideal but they have little affect on overall performance.

FYI, algaecide is fairly good at preventing algae, but not so much at killing it. We do no advocate "shocking" a pool.....too many failures. We SLAM the pool when we suspect organics. There is an article in Pool School explaining further

 

[Donldson]

I just want to back Dave up on this one. We have seen sooooooo many people come here with problems that they swear in no way can be chemistry related and then relate their problems to us and they are so clearly (to our very experienced eyes) chemistry related. Every single one of us starts from a position where we don't really know much about water chemistry, and that's not a problem, but when one does not recognize their inexperience and refuses to entertain the possibility that they might be wrong we end up at an impasse. So many problems could have been quickly solved with some test results, and so many threads got shut down because the OP got angry at the mere suggestion that they might be chasing the wrong problem and staunchly refused to post any.

All I can do is implore you to consider that Dave might be right. Because I can tell you that he probably is.

 

[BRENDAN M]

I just want to back Dave up on this one. We have seen sooooooo many people come here with problems that they swear in no way can be chemistry related and then relate their problems to us and they are so clearly (to our very experienced eyes) chemistry related. Every single one of us starts from a position where we don't really know much about water chemistry, and that's not a problem, but when one does not recognize their inexperience and refuses to entertain the possibility that they might be wrong we end up at an impasse. So many problems could have been quickly solved with some test results, and so many threads got shut down because the OP got angry at the mere suggestion that they might be chasing the wrong problem and staunchly refused to post any.

All I can do is implore you to consider that Dave might be right. Because I can tell you that he probably is.

I am certainly open to any and all solutions. The water being the issue would be the easiest and cheapest to fix. I came here with an open mind because I don't know what is causing my problem.

All I am trying to get a across is that I may not know a ton about pools but I have certainly have become a journeyman when it comes to water. I test my water with a Taylor kit daily and make adjustments. I know my water does not have Algae in it but lets assume that for some reason Algae formed in 44 F water and is somehow not showing up in my testing even after using an Algaecide and shocking the pool twice.

Can you advise what the next course of action should be?

Thanks again for your time.

 

[BRENDAN M]

Can you post current test results?

Can you see the backwash? Is it dirty?

A working psi gauge is virtually mandatory when troubleshooting your circulatory system.

The 90 degree turns are not ideal but they have little affect on overall performance.

FYI, algaecide is fairly good at preventing algae, but not so much at killing it. We do no advocate "shocking" a pool.....too many failures. We SLAM the pool when we suspect organics. There is an article in Pool School explaining further

Thanks Dave,

The backwash is not dirty at all but there are a ton of bubbles generated for a few minutes after the backwash is complete.

I have ordered a new gauge from Haywood and will get accurate readings when it arrives.

I am currently out of town and will not be able to post readings on the pool for a few days. My wife is happy to add pucks to the skimmer basket but she doesn't do a great job with the drip kit.

I will post all this information when I can get it.

 

[swimcmp]

For a Pentair mastertemp 400,000 Btu heater they really recommend a filter with a 100 gpm capacity. Hayward needs to be involved in the question of wether or not your pump and filter are sufficient to supply the water needed to make your heater and uv system work. I suspect that a 1/2hp pump and a 44 gpm filter just are not big enough. You have no extra capacity for the pump once the filter starts collecting fine dirt and getting dirty. If it works fine for a day or two or three after a backwash it seems that pump capacity is maxed out before you even start.

 

[BRENDAN M]

Hi Guys,

I want to give you an update on my situation. After testing the water again and verifying that it was perfect I ruled out water causing the problem. I then looked at the eyeballs and realized they were the smallest on the market so replacing them to create more back pressure was not an option.

I decided to replace the pump and upgraded from a 0.5 hp Hayward Super Pump to a 0.75 hp. I am happy to report that for 8 days in a row the fault light on the UV has not come on and the heater has not flashed "LO". The system seems to be working perfectly.

I am really pleased as the longest I have ever gone without having to back flush since the pool was put in was 3 days. The larger pump has seemed to fix the problem. I replaced the gauge and it is reading 14 with the new pump.

Thank you everyone for your help!