Cyclical Sudden Pressure Drop Syndrome


Old 09-02-07, 10:52 AM
dgabriel's Avatar
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Join Date: Sep 2004
Location: Connecticut
Posts: 38
Cyclical Sudden Pressure Drop Syndrome


I have a Pentair 60 FNS DE filter. Yesterday i backwashed and replacedd the DE. Today, it is going through the following cycle:

1) I turn on the pump, after about a minute, water starts flowing from the skimmer
2) Water flow steadily increase and pump pressure rises (from 0) As the flow reaches its maximum rate as indicated by the clear plastic pump chamber, andthe presssure is hitting about 13-15 psi, simultaneaously, the pressure drops and the water flow ceases, only to restart this cycle anew.

I though maybe I put in too much DE (8 lbs) but it isn;t too much> backwashed and recharged anyway, but the problem still exits.

Is it the filter element. Why is the systems in effect shutting down when it reaches what should be standard operating flow and pressure?
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Old 09-04-07, 08:45 PM
todrut's Avatar
Join Date: Jun 2007
Location: USA
Posts: 1,212
You have an air issue, sounds like your water level is low. If not then there is somewhere your pump is sucking air when it reaches full prime and then loses its prime. Check water level and pump basket gasket.
Old 09-14-07, 08:45 PM
Pool Guy's Avatar
Join Date: Sep 2007
Location: NY
Posts: 3
Fairly common problem with DE and Cartridge filters.
If the cycle for you goes, you backwash add fresh DE, start the filter and it runs great for a few minutes and then you get no pressure back into the pool, and the gauge maxes out, only to repeat the process of backwash, add new, runs great then no pressure. Then the problem is that the element on the inside of the tank needs to be acid washed or scrubbed by a similar method. Algae or minerals will coat the inside of the filter element (cartridge, discs fingers, grids) not allow water to pass through. The backwash helps if but only briefly.
DE and Cartridge filters are so good at filtering out these particles that they often need to be flushed once every other year to clean out the residual minerals. Maybe even more if you had a bad algae problem.
The way to DIY is to take a 5gallon plastic bucket fill it with two gallons of water and add a gallon of muriatic acid. Let the filter element soak for 4-6hrs (turn it over if you need to get the other side) the acid/water will almost turn mint green. Remove the element and wash out the residue a hose before returning it to the filter. If Muriatic
acid is not avail, the household cleaner "simple green" has also been used with success keep the ratio the same and let it soak 8-10 hrs.

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