Biodesign Pools not holding chlorine

[Reynbob]

Biodesign pools have a porous material layer over a Goodyear rubber liner. That material allows the weight of the water to rest directly on the liner therefore Biodesign pools have no rebar or gunite. The porous material can allow minute organics (pollen & algae) to settle onto and seep down to the  top of a hidden liner. The pools are not holding chlorine. Could it possibly be ammonia coming from the decomposing organic matter? This organic matter is very difficult to remove and will not vacuum up. It is my understanding that ammonia will bind with chlorine very quickly. On a 9,000 gal Biodesign pool ... add 10LBS cal-hypo... and within hours ZERO chlorine. Would anyone know if Bromine is affected by ammonia in the same way? I am just assuming ammonia because we have drained, pressure washed, and refilled several of them. As it's being washed (walls/floors) a greenish black sludge is washed to the bottom MD. We are in central TX and an area of pretty heavy Oak pollen. General water chemistry (pH, Alk, CH) is maintained. I do not see any topics related to Biodesign pools on these water forums. Thanks. Pool Builder in Texas.

[waterbear]

Are you using stabilizer (cyanuric acid)? Cal Hypo is an unstabilized chlorine source and the chlorine can be destroyed very quickly by UV from the sun if 30 to 50 ppm CYA is not added. What strength cal hypo are you using? 10 lbs of 48% (commonly available strength)  in a 9000 gal pool will raise FC by 43 ppm and calcium hardness by 45 ppm while 73% will raise the FC to 96 ppm and Ch to 68 ppm. I suspect that you have  algae growing in the pool since you describe a greenish black sludge. This could explain your problem, especially if there is no stabilizer (which would be why the problem started in the first place). I have a very limited knowledge of biodesign pools but my understanding is the top layer is resin and sand over a liner so it would seem to be like a flexible aggregate finish and would be similar to a liner or fiberglass pool in terms of water balance less like a plaster/aggregate finish by not have the problems of rising pH from fresh plaster and worrying about the calcium saturation index to protect the finish from scaling or pittitng.

[waterbear]

13 hours ago, Reynbob said:

It is my understanding that ammonia will bind with chlorine very quickly.

yes but you will still test as combined chlorine (monochloriamine) which is actually a good algaecide. In fact, there are products on the market to kill algae that are nothing more than an ammonium salt to form monochloramine and in the old days ammonia was often used as a chlorine 'stabilizer' before the common use of cyanuric acid and stabilized chlorine sources. There would also be a very strong "chlorine" smell from the monochloramine. (Think busy public pool at the end of the day when everyone's eyes are starting to burn and the smell is very strong.) As far as bromine, i would not recommend it for an outdoor pool since it cannot be stabilzied against decomposition from sunlight. It's fine for an indoor pool or a spa that is covered when not in use but not a good choice for an outdoor pool.

[waterbear]

Just to clarify, a Biodesign pool is not the same as a 'natural' pool. Biodesign pools are liner pools with a resin shell that have beach entries and are built to look like a pond. It is a construction technique that uses no concrete but can have a custom design like a concrete pool. It is not a 'natural pool, which is a pool that uses no chemicals but relies on an ecosystem of plants, anerorbic and aerobic bacteria, and gravel to 'filter' the water, much like a natural pond. The water is not sanitized and can contain harmful organisms such as Naegleria fowleri, also known as the 'brain eating amoeba'.

[PennyRealtor]

What happened with this pool? I am thinking of getting a bio design pool in Georgia