Poor suction

[Hansenaz]

My in-ground pool with DE filter and fairly new variable speed pump has always run with a pretty high back pressure (30PSI) and has had mild green algae problems (brush the walls weekly) for the last couple summers. When suction got a little low (judged by slow crawler) I'd backwash a little, not always topping up the DE every time. This worked OK for a couple seasons. (I keep lots of Cl in there and the chemistry checks out OK.)

Lately the algae was building up faster (odd in the cooler temps), the pressure was heading up to 35PSI and backwashing didn't help the crawler much. Never had this before.

I thought (confirmed at the local pool shop) that my filter must be clogged with algae so I took the filter apart and cleaned it pretty good. But this didn't change a thing. 35PSI, hardly any suction.

Switching between skimmer, crawler, and spa I can see there is no input clog. Doesn't seem to be air in the DE filter tank when it's running. I can switch output to pool or spa and that doesn't change anything.

What am I left with? Some clog after the filter (pipes go through a heater) but before the pool/spa split? Something with the pump? (I haven't messed with it but I doubt it's seen much debris.)

Ideas anyone?

 

[JohnT]

A DE filter will always struggle if you have algae. They just filter so well they clog quickly. You can compound things by running the filter without enough DE as debris gets stuck in the grids. If your water has typical Arizona calcium levels, you may need to follow the manufacturer's instructions for acid cleaning your grids.

The first thing you should try is to run the pump with the filter set to recirculate. If the pressure is low there, the problem is dirty grids or an internal filter issue.

 

[Hansenaz]

Thanks for the quick reply...I am a little afraid that algae could still be clogging the grids....but I actually "high pressure" hosed them twice (a 2nd time after the first got me nowhere) so I just about convinced myself that couldn't be it (no improvement at all?).

Is there some guideline or rule or thumb about how fast a freshly cleaned, unclogged one should "gravitationally" drain?

I don't think I know how to adjust my valves to recirculate...that should bypass the filter? ... don't know that I can do that...is that a standard mode?

One thing that had occurred to me was to pull the filter assembly out of the housing and run it....would that do the same thing?

 

[JohnT]

Thanks for the quick reply...I am a little afraid that algae could still be clogging the grids....but I actually "high pressure" hosed them twice (a 2nd time after the first got me nowhere) so I just about convinced myself that couldn't be it (no improvement at all?).

Is there some guideline or rule or thumb about how fast a freshly cleaned, unclogged one should "gravitationally" drain?

I don't think I know how to adjust my valves to recirculate...that should bypass the filter? ... don't know that I can do that...is that a standard mode?

One thing that had occurred to me was to pull the filter assembly out of the housing and run it....would that do the same thing?

If your filter has a mutliport you can just set it to recirculate. Running without the grids should work if your filter will go back together. It would be helpful to include information on your filter brand and model as much of the advice is model specific.

 

[Hansenaz]

If your filter has a mutliport you can just set it to recirculate. Running without the grids should work if your filter will go back together. It would be helpful to include information on your filter brand and model as much of the advice is model specific.

Thanks again John. Unless I'm missing something, I don't have a multiport valve. It's a newish Hayward DE filter (I haven't figured out yet if it's a 36, 48, or 60).

I was thinking I could pull the whole grid assembly and just let the in in-pipe flow straight into the tank. Any problem with that?

 

[JohnT]

Thanks again John. Unless I'm missing something, I don't have a multiport valve. It's a newish Hayward DE filter (I haven't figured out yet if it's a 36, 48, or 60).

I was thinking I could pull the whole grid assembly and just let the in in-pipe flow straight into the tank. Any problem with that?

Hayward makes more than one type of DE filter. The same filter can be equipped with a push-pull valve or a rotary multiport valve.

 

[Hansenaz]

Hayward makes more than one type of DE filter. The same filter can be equipped with a push-pull valve or a rotary multiport valve.

I've got a push-pull.

 

[Hansenaz]

Hayward makes more than one type of DE filter. The same filter can be equipped with a push-pull valve or a rotary multiport valve.

Well I did the experiment. Pulled out the entire grid filter assembly, closed it up, and turned it on. Crawler ran like a race car. I assume this means my grids are blocked...probably with Calcium (they looked clean after a couple hosings). So I guess I need to go through the TSP and acid soak/clean procedures I've seen on the internet.

Nagging concern...green algae is continuing to build up on the floor and walls (and I've had ~10 days of bad filtration) in spite of good Chlorine level + two bags of Ca shock. By the time I get my grids clean and back in I'm facing a DE + algae mess (yard is already bad enough after the last few failures). Any suggestions based on experience?

 

[pooldv]

More here about cleaning a DE filter and grids
Pool School - Maintenance and Cleaning of Pool Filters
Use and care for DE filters

If you have algae in the pool then follow this process to kill it, SLAM Process. Algae will clog a filter in a matter of hours, especially DE filters.

 

[Hansenaz]

More here about cleaning a DE filter and grids
Pool School - Maintenance and Cleaning of Pool Filters
Use and care for DE filters

If you have algae in the pool then follow this process to kill it, SLAM Process. Algae will clog a filter in a matter of hours, especially DE filters.

Thanks...
I do need to knock that stuff out but I have a chicken and egg problem with a little chicken and big egg. The suction is so bad I can't really vacuum out algae and the algae problem is pretty minor (blue pool with slow build-up on walls and bottom). I'm thinking if I can get the suction back (and by now I guess that's acid cleaning grids), I can deal with the algae without much trouble. The SLAM info helps...thanks again.

It's pretty clear it's not the algae causing the high back pressure low suction problem because a couple grid cleanings didn't change a thing...

 

[xyz]

Yes, if you can remove the internal elements this bypasses the filter; this would give us good information.

I've learned that some Hayward DE filters can have fairly high backpressure, even when working perfectly, so this may be what you are up against.

I'll say my new Quad DE filter has low flow friction, to the point where the needle doesn't come off the pin at 0psi during normal operation. So it is a great compromise between a cartridge filter [low flow friction], and a DE [very fine particulate removal].

Also, seems like it is almost as easy to clean as a cartridge filter.

 

[Hansenaz]

Yes, if you can remove the internal elements this bypasses the filter; this would give us good information.

I've learned that some Hayward DE filters can have fairly high backpressure, even when working perfectly, so this may be what you are up against.

I'll say my new Quad DE filter has low flow friction, to the point where the needle doesn't come off the pin at 0psi during normal operation. So it is a great compromise between a cartridge filter [low flow friction], and a DE [very fine particulate removal].

Also, seems like it is almost as easy to clean as a cartridge filter.

Thanks for the info on the Quad filter. My Hayward housing was replaced just a couple years ago so I'm not really looking for a full replacement. And it looks like I may get new grids rather than clean them (I gotta go to work!) because the pool shop is coming out tomorrow. I'll put up the (final) solution soon hopefully.

 

[xyz]

Makes sense. I didn't intend you to throw out a perfectly good Hayward filter; more like, don't necessarily expect every DE filter to be either low flow or high flow. Depends on the filter.

Good luck!!

 

[Hansenaz]

Makes sense. I didn't intend you to throw out a perfectly good Hayward filter; more like, don't necessarily expect every DE filter to be either low flow or high flow. Depends on the filter.

Good luck!!

Well here is the word from the pool guy: he ran the pump with the filter grids out (like I did) and observed good suction (like I did), but also high back pressure (32PSI) (which I didn't check because I was in a hurry). So he cut off the PVC heading from filter to the heater (not used in 10yrs) and saw the heater line was full of rust. He looped out the heater and system PSI went down to 12PSI.

So the problem was a line blockage in the heater. Funny that was next on my list to check but I was fooled by the large suction increase I saw when I pulled the grids. I guess both the blockage and grids are drags....so I'll be getting new grids too. And probably new water to finally solve the algae...

Thanks everyone for your comments.

 

[zea3]

You might not need to replace the water. What are your current test results?

 

[Orlando112]

Heaters, tablet feeders (especially when they get old), adjusting valves improperly and clogged spa venturis can also cause the pressure to go up so pay attention to those factors too.

 

[Hansenaz]

You might not need to replace the water. What are your current test results?

Frankly I can't remember the details (and I'm a chemist!). But when discussed at the pool shop the other day we concluded I could probably go another year. But the water is about 8 yrs old and prone to algae so I'm thinking replacement may make more sense than aggressive algae treatment.

- - - Updated - - -

Heaters, tablet feeders (especially when they get old), adjusting valves improperly and clogged spa venturis can also cause the pressure to go up so pay attention to those factors too.

Thanks
I did a lot of checking of those things so grids or "after filter but before spa/pool out valve" had to be it. The heater fits into the after filter category so its logical at this point.

What to do about a dead heater? I'll start another thread I think.

 

[JohnT]

Frankly I can't remember the details (and I'm a chemist!). But when discussed at the pool shop the other day we concluded I could probably go another year. But the water is about 8 yrs old and prone to algae so I'm thinking replacement may make more sense than aggressive algae treatment.

Water doesn't become algae-prone because of age. It's simply a lack of chlorine or excessive sanitizer for the chlorine level. Changing your water would accomplish nothing, but changing your chemistry will prevent you from ever having algae.

 

[pooldv]

My water is 5 years old and has never looked better. Oldness is goodness, and chlorine is your friend.

 

[Hansenaz]

Water doesn't become algae-prone because of age. It's simply a lack of chlorine or excessive sanitizer for the chlorine level. Changing your water would accomplish nothing, but changing your chemistry will prevent you from ever having algae.

Well I'm thinking phosphates for the algae (which I know are somewhat treatable)...but also general "accumulators" like hardness. I always have kept high Chlorine. So do you think water never needs to be changed? I don't have a strong opinion but I'm told that my water is "old". I've definitely had more of an algae problem last couple seasons...I've thought it might be related to neighbor's ficus tree megadump into my pool (cut it back last year).