First off back on the topic of how to drain, since you don't have a waste setting, but are potentially planning on a major DE filter cleaning, you could probably remove the grids from the filter, and drain to backwash while the grids are out being cleaned, then put them back in after you are done draining. This assumes that your model of filter does not have some feature that prevents it from operating with the grids removed, I have never heard of one that does, but don't know all that are out there.
Now down to the advice of the pool guy, If it were me I would run away from them, because it is clear to me they do not have a good understanding of safe pool operation. There are several clues in their advice that make me think that, the first is their use of copper based algaecide (or most any algaecide without special consideration). There are 3 major problems with copper based algaecide.
1, It can leave metal stains in the pool, and can even make the water turn colors if enough copper builds up.
2, It can make hair turn green, particularly people with blond hair.
3, This is the one that may not make sense at first, in high enough levels (usually enough for 1 and 2, to happen) it can also prevent algae from growing when there is low FC. You may think this is a good thing, but let me explain why it is not. Algae is not the only nasty thing that we want to keep out of pools, we also want to control bacteria and waterborn viruses. The problem is Algaecide only stops algae from growing and does little or nothing for the the other two, which are invisible to the human eye and not detectable with common consumer tests. Therefore we rely on the lack of the visible presence of algae as a proxy to tell us if our sanitizer (usually Chlorine in this case) is at effective levels to kill all of the things that might be growing in the water.
After reading this you can see how your pool guys advice to run a pool with algaecide and depressed FC levels could potentially lead to a clear but unsafe pool.
Ike
Now down to the advice of the pool guy, If it were me I would run away from them, because it is clear to me they do not have a good understanding of safe pool operation. There are several clues in their advice that make me think that, the first is their use of copper based algaecide (or most any algaecide without special consideration). There are 3 major problems with copper based algaecide.
1, It can leave metal stains in the pool, and can even make the water turn colors if enough copper builds up.
2, It can make hair turn green, particularly people with blond hair.
3, This is the one that may not make sense at first, in high enough levels (usually enough for 1 and 2, to happen) it can also prevent algae from growing when there is low FC. You may think this is a good thing, but let me explain why it is not. Algae is not the only nasty thing that we want to keep out of pools, we also want to control bacteria and waterborn viruses. The problem is Algaecide only stops algae from growing and does little or nothing for the the other two, which are invisible to the human eye and not detectable with common consumer tests. Therefore we rely on the lack of the visible presence of algae as a proxy to tell us if our sanitizer (usually Chlorine in this case) is at effective levels to kill all of the things that might be growing in the water.
After reading this you can see how your pool guys advice to run a pool with algaecide and depressed FC levels could potentially lead to a clear but unsafe pool.
Ike
I keep scrolling up and down and whaaa? Then I remember I noticed it yesterday. lol Confused.
