Insufficient backwash?

[Hansenaz]

My main battle with my pool for 20+ years is maintaining enough suction to keep my skimmer skimming and my Hayward crawler crawling. As the DE filter clogs and the back pressure rises this gets harder and harder. Not enough suction to go around.

This year installed new DE filter grids and was amazed at how good the flow was. Crawler was moving even when high speed (2800 rpm) switched to low speed (1500 rpm) and the water fall stayed strong as well instead of turning to a dribble.

After a Phoenix monsoon dropped a bunch of dirt and leaves in my pool a couple days ago I worked to clean it up, noticed the waterfall and suction was weak even at high speed, and so I did a first backwash. I did a 2 min backwash, water looked clean, then recirculated pool for ~15 min before another 30 sec backwash. Added 4-5lbs DE and while it now runs OK, it seems the vains are not transmitting nearly as well as when the grids were new...suction is back to marginal.

Would more backwash have helped? Another explanation?

 

[ajw22]

What model DE filter are we discussing?

 

[Hansenaz]

It's a Hayward Progrid - don't see the model - about 10yrs old 3.5ft tall, takes 7.5 grids.

 

[ajw22]

You need to follow this backwashing process…

How To Backwash a Hayward DE Filter - INYOPools.com

This guide shows you the steps required to Backwash a Hayward Pro Grid DE Filter.

www.inyopools.com

 

[Hansenaz]

Thanks Allen. My setup doesn't have a rinse position just an up/down valve that switches from pool recirculation to sending the water out. I attach a picture. I'm not sure what physically is happening in each of the steps, particularly the rinse.. Obviously backwash is supposed to send water through backwards blowing the dirt and DE out. I sort of figured that recirculating after this might redistribute some stuff allowing another backwash step to be useful. But what I did apparently left too much dirt in it (right?). So I need longer backwash, ;longer rinse, more steps?

 

[ajw22]

You have a Slide Valve, not an MPV.

All it can do is backwash. Not much more you can do with it.

You can break down the filter and clean the grids manually and see if they flow better.

Slide Valves - Further Reading

www.troublefreepool.com

 

[Hansenaz]

Right...I hate to do that and really want to be sure it's not just insufficient back wash. I will run in it in this "disappointing mode" until I need another full backwash (we got more monsoon coming this year no doubt) and then backwash the heck out of it.

Really my initial question is should I expect to loose so much of the initial "good grid flow transparency" after the first backwashing?

 

[ajw22]

A backwashing is never as good as a grid cleaning. You always give up some flow with just a backwash and not a full cleaning.

What is your clean filter pressure?

What was your filter pressure before you backwashed?

What pump do you have?

DE Filter Use and Care - Further Reading

www.troublefreepool.com

 

[Hansenaz]

Pressure has been definitely weird. Before the new grids it'd sit at 12psi when good and get up to 20 when very dirty. After the new grids it was about 8, but even after the recent monsoon and poor suction it was reading only 6. At the moment after cleaning and with "disappointing" suction (i.e. much less than new grids) it's at 9psi. I'm taking the amount of suction I see (Crawler + skimmer) and waterfall flow as better gauges of health than the pressure at the moment. It's a Hayward variable speed pump, about 8years old.

I've looked for blockages in suction lines to see if that could be a problem, but they look good.

 

[Hansenaz]

Update for anyone who reads this thread. After a couple weeks of normal use the system flow slowly improved (as judged by suction and waterfall flow) to where it's only a little less than I saw with the new grids. Not sure how to explain this time-dependent improvement but if the initial problem was "insufficient backwash" it's sorted itself out.

 

[mknauss]

Check the impeller for any items stuck in it. Palm strings are especially a problem. Use hair nets in the skimmer basket(s) to reduce them getting to the pump .