High pressure at filter, low after

[Ny2Tx]

So here's what I'd like some input on:

The pressure at my filter used to be around 20-25psi for the couple of years that I have owned my pool (since 2009). When the filter got clogged with algae it would creep up to around 30 if I remember correctly. Recently however the pressure is around 29-30 even when the cartridges have been recently cleaned. I have a Pentair Caretaker in-floor cleaner and the pressure reading at the valve is only 9-10psi. It seems to me this is a too large pressure drop. Also putting my hand in front of the jets in the pool it seems they do not to have the same force that they used to.

The cartridges in the filter were replaced in 2011.

 

[mas985]

Sounds like the cartridges are clogged again. But if the filter is getting clogged with algae, you need to kill the algae first and then keep your FC level high enough so you don't ever get algae (see Pool School).

AFTER the algae is dead and removed from the pool via vacuum to waste, then clean the filter per Pool School recommendations.

 

[JasonLion]

Welcome to TFP!

If your numbers are right and there isn't any algae, it does sound like there is a problem. The pressure gauges used on pool filters are not all that robust and can easily break, so it good to get confirmation by feeling the return pressure, as you have done.

Have you ever done an overnight soak in detergent for the filters? Hose off normally, then soak overnight in a mixture of one cup of automatic dishwasher detergent for every five gallons of water, then hose off again and re-install in the filter. Another possibility is calcium scaling on the filter cartridge. This is usually fairly obvious on a visual inspection as the filter fabric gets stiff and white chalky deposits should be visible on the fabric.

 

[Ny2Tx]

Wow, thanks for the quick responses!

Water has been clear lately so maybe I just did not get the cartridges clean in the first place? I usually just spray them with the garden hose.

I will try the overnight soak. So do you use the bath tub for this or is there a better solution?

The pressure gages are fairly new and seem to be working fine.

 

[mas985]

When the filter got clogged with algae it would creep up to around 30 if I remember correctly.

So did you really mean dirt instead of algae?

I use a large plastic garbage can to soak my cartridges. TSP works the best but automatic dish washing detergent also works well.

 

[Ny2Tx]

When the filter got clogged with algae it would creep up to around 30 if I remember correctly.

So did you really mean dirt instead of algae?

I use a large plastic garbage can to soak my cartridges. TSP works the best but automatic dish washing detergent also works well.

What I mean is after I had an outbreak of algae turning the water green and after I had shocked the pool and cleaned out the green stuff I'd notice the filter pressure increasing. So I'm assuming it was algae to a large extent...

I think I've heard that even 25psi (my normal reading) is on the high side for this type of filter...

Oh yeah a garbage can should work! I could not think of suitable size container. Thanks!

What is TSP? Something I can buy at the pool store?

 

[JasonLion]

TSP is trisodium phosphate, an especially effective cleaner that is outlawed in many parts of the country due to water pollution issues. Both hardware and grocery stores have it in some areas, but be careful not to be fooled by cleaners labeled TSP which actually contain something else.

 

[Safetybob]

Jason, what would you recommend as a rule for cleaning/soaking cartidge filters. Or perhaps would you agree with this:

1. TSP
2. Dishwashing detergent
3. Laundry detergent

I was advised I think close to 2 years ago that soaking my filters in ordinary liquid laundry detergent would be the way to go. Also, if I can't find "real" TSP at the store, is liquid dishwashing detergent OK, or must I use a dry dishwashing detergent and mix it up.

Bob E.

 

[mas985]

You need to be careful about generating suds which is why I would not use laundry detergent or any regular type of soap. Also, make sure it is AUTOMATIC dishwashing detergent, again to minimize suds.

 

[JasonLion]

Real TSP is best, if you can find it. Powdered automatic dishwasher detergent seems to come the closest to the effectiveness of TSP without the problems (like excessive suds) that some of the other alternatives have plus it is universally available.

 

[bobodaclown]

TSP can be found at Lowes/Home Depot and such, usually in the paint department. It's used to wash walls prior to painting.

 

[Ny2Tx]

How much TSP to use, If I can find it?

I will check my local Home Depot.

 

[JasonLion]

It's the same as the detergent, one cup for every five gallons.

 

[Safetybob]

Perfect, thanks Jason. Will go get some to have ready for the season.

Bob E.

 

[Ny2Tx]

Would it harm anything to run the pump while the filter cartridges are removed and soaking in the TSP/Dish washer solution?

 

[mas985]

Can you bypass the in-floor cleaner? If not, without the filter there is a risk of clogging a head or zone valve.

 

[Ny2Tx]

I can bypass it by sending the flow to the "waterfall" but I originally was thinking I'd let the in floor cleaner run. There's a steel "strainer" that collects debris before the valve. Often, after I have cleaned the filter some debris is flushed out from the filter and gets stuck on that strainer so it seems to work....