What would account for start-up filter pressure (following backwash) being nearly as high as before backwashing?

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anthonypool89

Gold Supporter
Aug 26, 2016
571
Berks County, PA
I backwashed today at approximately 20 lbs as usual. I was not yet in a no-flow situation (as indicated on the heater), but the flow was surely reduced coming from the return lines. The grids have been chemically cleaned only a few days prior to going in the DE tank. Start up pressure at that time was 15. The cycle lasted only a few days until the pressure got up to 20, so I figured I might as well do it again today. These short cycles have been plaguing me ever since opening the pool end of May. And, start-up pressure has been increasingly higher as the weeks go on. What was always a start-up of 11 lbs for probably the last 20 years is now suddenly 14, 15, and climbing.

So getting back to today- immediately after backwashing, taking out the grids and using high pressure nozzle to clean them off real well, putting them back in, turning on the pump - my pressure was 19 - only ONE pound lower than before I took anything apart! This is a totally unprecedented startup pressure in my 31 years of operating the pool. And, even more amazing to me, is that I had not yet put in any DE. All this, to me, makes absolutely no sense but seems indicative of either a suction side blockage of some sort (or other blockage somewhere in the system -perhaps coming out of the pump). Or possibly issues with the pump? The gauge is brand new - one of these glycerin filled that shows 1/2 lb. increments - so it should be accurate.

The next time I take the tank apart - which will surely be soon - I want to try running the pool without the grids just to see what the start-up pressure is. .I've run the pool many times this way over the years whenever we've gone on vacation during the swimming season. That way I never have had to worry about pressure increase. The pressure without the grids has always been, without fail, an unwavering 10 or 11 lbs. IF it's that way again, then I'm really not sure what's going on with the grids or plumbing or whatever else. However, if the pressure without the grids IS unusually higher than 10-11, I think that pretty well supports my theory that more than just chemistry is at work here.

Thoughts or suggestions??
 

anthonypool89

Gold Supporter
Aug 26, 2016
571
Berks County, PA
I've been using a product called Aqua Finesse tablets over the past few years. Two main ingredients: sodium carbonate (30-50%) and disodium metasilicate (20-30%). Not only have I been using it, but I've been using a double dose weekly. As a result, I have constant pH bounce - the AF increases by at least .4 - and then I have to add decreaser. (Just occurred to me it's sort of like I've been dumping boxes of soda ash in the pool every week). The main reason for the thread, however, is the question of filter pressure. EVERY time I add this stuff (in the form of round pucks) to the skimmer, within 1-2 hours I have filter pressure increase of a few pounds. Typically, over the years, it usually went back down somewhat - sometimes to the level it was at before AF, but sometimes not. Lately, though, I'm seeing these unusually high and sustained pressure levels. Is it possible that a built-up of this stuff - from years of using it - is resulting in a near constant pressure increase? Once the stuff dissolves, could the individual molecules be doing the same thing that biguanide molecules do - that of not being small enough to pass through DE and thus contributing to coagulation? OR is the AF simply releasing biofilm from the lines thereby also inducing coagulation? If the latter, it seems odd that the pressure increase would occur so quickly and then - as in the past at least - revert back to a lower point. Any thoughts from those who know the chemistry better than I?
 

anthonypool89

Gold Supporter
Aug 26, 2016
571
Berks County, PA
I don't understand why this thread was moved out of "deep end". My inquiry was primarily chemistry-associated. This way all that has happened to a new inquiry is that it has become merely a reply to my own thread, which didn't meet with any responses. That's why I wanted it separate. Not happy.
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
14,445
Evans, Georgia
Your questions are all related to your problems with Bacqua. Starting multiple new threads risks conflicting information and the risk of posters answering one thread without knowing of the other issues.

Remember, TFP is a chlorine based pool care system and very few people here know or use Bacqua products. You might find a Bacqua forum more helpful?

Maddie, TFP Moderator.
 

anthonypool89

Gold Supporter
Aug 26, 2016
571
Berks County, PA
Yeah...except I've never been able to find a Baquacil forum. Wish I could. I'm starting to feel a tad unwelcome here. There is little evidence of any focus on trying to help people who DO use biguanide other than to tell them all the reasons that they should convert to chlorine. I think it's time to stop posting. I appreciate the many responses, but most have been geared to trying to get me to convert. There is very little positive information here about biguanide, and I understand that. But, going forward, unless I decide to convert, there seems to be little point in continued discussion. I thought the metasilicate question was completely legitimate from a chemistry standpoint alone. There is definitely a closed-mindedness present here relative to any positive thoughts about biguanide - and I get that as well. OK...I get the hint.
 

kimkats

Mod Squad
LifeTime Supporter
Jul 10, 2012
46,382
Tallahassee, FL
As stated TFP IS a chlorine based system. We know it works with science and thousands of pools to back it up. I wish you luck with your use of Baquacil. Let us know when you are ready for a truly Trouble Free Pool.

Kim TFP MOD
 
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