25% ??

[keep-it-simple]

Pool school says to backwash when filter pressure raises by 25%.
I have an old pool... neighbors think the pool was dug in the early 80s.

When the pool is backwashed and all baskets clean - pump running at 2175 rpm - the pressure gauge reads 1.5psi. So I need to backwash when the pressure gets up to 2psi while running at 2175rpm?

 

[mas985]

At low RPM, PSI readings are not very accurate so pick an RPM where the clean filter pressure reads 16 PSI and then periodically return to that same RPM to check the filter and when it reaches 20 PSI, clean the filter.

 

[keep-it-simple]

pick an RPM where the clean filter pressure reads 16 PSI

3400rpm is as high as it goes and that only gets the PSI up to 8. So check it at max speed and backwash at 10psi?

 

[jblizzle]

Yup

Wow that is a very efficient plumbing install if you only have 8 psi on that big ole pump ... unless the suction side is somehow very limiting.

 

[mas985]

Yea, that doesn't sound right. What make/model pump do you have? Can you describe your plumbing?

Pipe diameters, lengths and number of the runs from pool to pad

Could be a bad pressure gauge.

 

[keep-it-simple]

I don't know how to determine what you're asking, man.

The gauge is brand new. Someone here sent me a link to it.
The gauge was reading as high as 18-20psi daily when the GA pollen was high in the spring. I'd backwash it down to 1 and it'd be up to 20 within 36 hours.
The piping is 2.5" diameter. The skimmer is roughly 18' from the filter, and the filter is 3' from the pool. There are two return lines: about 3' from filter and maybe 30' from filter.

I think the pump is Jandy. 2HP maybe? I can't see the label. The pump controller is by AO Smith and ranges from 600rpm to 3400rpm. 2175rpm is needed for the SWG to operate when the filter is clean, so that's what I run mostly.

 

[jblizzle]

If you used to see high pressure and do not anymore, then I bet your impeller is clogged up with something.

You might be able to tell by looking through the pump basket, but easiest to check and clean if you pull the motor off.

 

[keep-it-simple]

I only saw high pressure when the pollen was high. I'm talking it looks like a cloud of dust there's so much pollen in the air and the surface of the pool is yellow.
I'd backwash the filter to 1. I had the filter running 24/7 to work on aerating and acid for TA plus keep the pollen in control. The pressure crept up throughout the day and I'd backwash it down to 1 again. That was only an issue for maybe 2 weeks. The filter pressure stays under 10 otherwise.
I just cleaned everything out real good less than 3 hours ago. Vacuumed, brushed, and backwashed approximately 1200 gallons (3-4") plus a 5+ minute rinse. When I kick the pump up to 3400rpm, the return lines spout water higher than the deck surface. I'd be surprised if anything was clogged anywhere. :?

Would a pool service be able to troubleshoot the filter if the pressure is a problem? I just had them out here last week to repair a leak. He said everything in the filter and skimmer looked good - leak was found in the liner next to the skimmer.

 

[jblizzle]

Well, if the water flow is that good, maybe the impeller is fine and you just have a very low headloss.

 

[duraleigh]

I'll bet there is a suction side restriction or the filter is a monster. That clean psi is too low for a normal system.

 

[keep-it-simple]

:?:
It says it can handle up to 50psi. Not that I'd ever let it get that high...
I'd say the bulb part of the sand filter is at least 3' tall. I can't reach my arms around it.
How would I determine restrictions?

 

[mas985]

2175rpm is needed for the SWG to operate when the filter is clean, so that's what I run mostly.

This is a clue that something is wrong. That is much too high of an RPM to get the SWG to work properly. That means that the flow rate at that RPM is is around 15-20 GPM. For a normal setup of 2" plumbing (smaller than yours), the flow rate should be around 60 GPM.

First thing to check is to remove the pump basket and reach down into the inlet and see if there is anything stuck in there. The next thing to try is to put a hose in the pipe that enters the pump (through the pump) and try to flush any debris backwards towards the skimmer. Wrap the hose with a rag to help seal it against the pipe.

A better picture of your pad equipment might help too.

 

[keep-it-simple]

I've taken apart everything that looks like it might come open. I've hosed everything out. I poked around/hosed out anything open enough to poke.
I do have a concern about my filter -I'll try to describe that separate.
But here's what I've got: (thumbnails open to larger photos)

Ranger series 36" sand filter. Diameter is wider than my arms.
Here's a shot from my kitchen:

Pump is Hayward 2.7 HP.
SWG is Jandy Ei series (requires min 4000ppm salt rather than standard 3000ppm)
Motor is AO Smith variable speed/timer.

 

[keep-it-simple]

Regarding filter...

Okay. Lemme see how my vocab is.
Pump/motor lead up to SWG then across multiport main valve into filter. From multiport main valve, there's a ball valve then pipe out for back washing / wasting.
It's like the multiport main valve is loose. When I have the main valve set to filter, I have to close the ball valve for water to stay in the filter, otherwise it wastes and filters. Then I open the ball valve when I'm back washing or wasting. So there's inefficiency there; I just don't know how significant that is.

 

[jblizzle]

Whoa ... the SWG should definitely NOT be before the filter ... explosive gas could collect in the filter (although less of a concern given the top-mounted valve). The SWG should be the last thing before returning to the pool.

If you are getting water out the backwash hose when the multi-valve is on filter, then clearly either the spider gasket is bad or the valve is not seating properly. If the valve is not seated, then you could be having a lot of water bypassing the filter and heading right back to the pool ... thus resulting in lower pressure in the filter.

 

[keep-it-simple]

(>_<) Lemme get a closer shot of the pipe set up for you and make sure I've described it all correctly.

 

[Guest]

Fortunately I was wrong about the direction of water flow.
But it does seem I'll need to open the main valve and troubleshoot in there. I'm guessing the main valve and enclosed spider gasket are replaceable?

 

[jblizzle]

OK, good deal that the plumbing order is fine. Clearly something is "off" in the multivalve that is allowing water to the waste pipe when it should not ... and could be the cause of the low pressure.

The gasket and parts are replaceable. Check the gasket or maybe the spring has gotten weak and not forcing the seal?