DE Filter Pressure Never changes (adding DE, over time, etc)

[wpb]

I've had a problem that has not affected my pool-clarity, so I've essentially let it slide. However, the more I read the forums, the more I'm concerned by the issue and if nothing else, figure I should at least understand why its happening.

My DE filter (Hayward ProGrid 24 Series, the DE2420 Model) is behind a Pentair Whisperflo pump (2 HP). It has the matching Hayward Six-Position Vari-Flo multi-port valve. These were all purchased new and installed about 3 years ago.

The pump has about 80' of head (if you consider all 90's, etc).

The reason for the fairly large pump / relatively small filter (the 2420 is the smallest, with only 24 sqft of filter) is because it powers our swim-spa (about 1,000 gallons). Therefore, even the 2420 is overkill; however, I think the 2 HP pump could possibly be pushing too much for this filter? I have no intelligent basis for that claim, simply a concern over the issue I'm about to explain.

When I first went to coat the filter (adding DE through the skimmer) I followed instructions. I carefully weighed out the DE, and put in the specified amount. Prior to the DE going in, pressure was about 29 psi. After the DE went in and equalized, pressure was still 29 psi. When the filter pump is off, pressure drops to 0 psi.

After 6 months of use (only gets 3 hours of recirc a day) pressure did not change, zero difference. I decided to let it continue filtering. At one year, still no rise in pressure.

At one year, I backwashed, removed the grid, and inspected everything (not really knowing what to look for, but it fit snug and there were no rips). Again went through the coating process, and received the same results.

29 psi before any DE is added, against a clean filter. 29 psi after DE is added. Doubled-up the DE (twice specified amount) and I still get 29 psi.

One year later, did the same thing (opened, inspected, replaced) -- same results.

Everything I read says that 2 minutes after adding DE into the skimmer, the DE filter's pressure should rise noticeably. What am I doing wrong?

I should also mention, the filter appears to work very well. I've had my pump stop while away on business, return to a pretty rough spa, and it will look crystal clear in about 6 hours with the correct chemistry.

Every now and again, when the filter is first coated (after adding DE) a little may escape into the spa, causing me to thing there is a very small leak. However, this is a very small amount and it's only when I first coat the filter, possibly the first 3 days or so after coating.

Thank you in advance

 

[waste]

Welcome to TFP!!

And Happy New Year

I'd have to say that it's the 2 HP pump that is keeping the pressure from rising, and causing the 'blowthrough' you noticed. Mas985 or Jasonlion can tell you the flow rates and head (and I believe that will confirm my suspicion).

Is there room enough to bypass some of the water from the filter? (i.e. have ~ 1/2 the water pass through the filter and the other 1/2 bypass the filter and go back into the pool) I, and a number of others here, can tell you exactly how to replumb the system to accomplish this - it be best if you could post pics of the system and tell us the pipe sizes

 

[wpb]

Thanks for the reply!

Everything is plumbed 2", and it's about 60' of head.

The circuit looks like this: Spa Skimmer/Intake > Jandy Check Valve > 2 HP Whisperflo Pump > Hayward Multi-Port Valve > Hayward DE2420 Filter > Heat Pump > Jandy Chlorinator Cell > Mineral Feeder > Out to spa.

Basically there are two pumps that run mutually exclusive of one another. One is the recirc pump we're talking about @ 2HP. One is a pump for jets @ 3HP. Each has a Jandy check-valve in front of them, so they can't suck water through the other.

Plumbing a 3/4" bypass (to circumvent the filter), allowing a theoretical 1/3 of the water to pass through, would not be too difficult since the in/out of the filter run parallel. My only question is whether its worth it. I mean, the filter appears to work -- although I'm no expert and can't be sure it's working particularly well. Perhaps its not working as well as it could?

Would the hassle of the plumb-around be worth it?

I could also post pics, but it's a bit of a complicated system and it might confuse the issue a bit (three pumps, Jandy & SWG, mineral system, all plumbed with 45's to keep head down, etc). That's what happens when a DIY'er does his own equipment pad, I guess ;-).

Thank you again for your help!

 

[PoolGuyNJ]

Your pushing close to 80 GPM. The filter is meant for no more than 48. Make a bypass using 1-1/2" pipe and put a 2 way gate valve for both adjusting and to prevent DE from getting by when recharging. You are squishing the grid fabric.

Scott

 

[duraleigh]

wpb,

Yeah, that's not a very efficient system. If you completely blocked the flow of water, you'd probably max out at about 35psi so you can see you have a lot of restriction from that filter.

 

[wpb]

Thank you both for the replies. The gate addition really makes a lot of sense, great idea.

One thing.. Is there any way to run a pump like this, at a lower power level? I realize they make two-speed pumps for this, but I was wondering about a less conventional method for someone like me who is stuck with a pump they really don't need.

When I bought the pump, I was only looking for a 1 HP; however, the source offered me a "scratch and dent" 2 HP for the same price, and I mistakenly went with that. That was several months before I found this forum, and a couple years before I made my first post .

If there is no workaround for running a pump at a lower-speed, perhaps I can simply purchase a 1 HP pump and bolt it in place, assuming the whisperflo uses the same internals for the full range of speeds (it appears that my 2 HP and 3 HP's are all identical, excluding the pump motor).

I just hate to bypass the filter, since I'm wasting power by pushing a recirc pump that is technically only recirculating a fraction of the water it passes.

Thank you again for all of the great insight!

 

[PoolGuyNJ]

If you didn't have a spa, I would say that was reasonable. How many jets are in your spa? You want at least 10 GPM per jet typically. If the spa is pretty much unused or only has four jets, dropping to a 1 HP motor is reasonable but it will need a couple additional parts.

The volute, impeller and seal set will also need to be swapped.

Scott

 

[wpb]

This pump is only used for recirculation, which is the reason I don't have any use for the power beyond filtering.

I have one 2 HP and one 3HP pump for the jets (it's a 12' spa), and believe it or not, those barely give the jets enough power. Sometimes I wonder if 2" pipe is a little small for 3 HP pumps...

When I've replaced the pump motor (with the same size motor) in one of my other pumps, I used a new seal set, but I was able to reuse the volute without any problem. Is the volute a "must" or just something that's a good idea when the pump is older?

I couldn't for the life of me see any difference in the impeller size between the 2 HP and 3 HP pumps (and I examined them back-to-back), despite them being different part numbers, that's why I wasn't entirely sure about whether there was a difference -- thank you for confirming.

 

[PoolGuyNJ]

When changing motor size, it is often the case. A single speed pool pump spins at 3450 RPM. Different HP motors have different amounts of torque available. Having an impeller for a 2HP motor on a 1HP motor will cause it to labor excessively. Since the 1 HP impeller is smaller, the volute would be too big, again causing the motor to labor. The seals should be changed as a matter of best practice to prevent leaks. The impellers for different motor sizes may vary in diameter and in thickness.

A 3 HP pump should have larger suction plumbing than 2". It could push over 140 GPM, given a proper hydraulic configuration where the water velocity in the pipe doesn't exceed 7 FPS (3" pipe required). Head loss increases very rapidly as the speed increases in the pipes.

I hope you have multiple drain sets in the spa too.

Scott

 

[wpb]

Wow, I just learned something new ... again. Scott, if I understand you correctly, you're saying that a 3 HP pump should use 3" plumbing on the incoming side, but outgoing is okay to be 2"? I had no idea the suction side required more volume, but I wish I had known before I ran all of the pipes!

I wonder if I should perhaps go through the trouble of ripping up pavers/etc, and plumb a second 2" for the suction side. Ugh..

 

[PoolGuyNJ]

Suction is a more dangerous thing in a body of water. The slower moving water found in large pipes can reduce the risk of entrapment because it's doesn't pull as hard. The use of newer VGB compliant suction grates also helps. Return inlets usually push you away from the opening but if a hand/wrist/arm is inserted, stuck and the pump turns on, problems can occur, especially if the stuck appendage swells.

Do you have a picture you can post of the spa? A top down view is usually best. I am particularly interested in seeing the suction outlets and return inlets. It is possible your drains may not be rated for the volume of water they need to permit safely. Adding a second 2" line may not help in increasing safety and may still limit your flow rates.

Many commercial pools had to do major renovation and retro fitting because they didn't meet the VGB standards. Existing residential pools were exempt, sort of. If it was getting renovated or a new liner, a new VGB suction grate had to be installed and all old style grates in the retail chain had to be disposed of. All new residential pools being built today must meet the VGB standards. Some local codes add additional requirements, as is their prerogative.

Scott