[AquaAddict]

Thanks everybody for going to the trouble to give such extensive advice.

Yes, it's 2.0 mg/l in the tap water and was slightly less after filtering. However, I gave my filter a good back flushing which I hadn't done since the spring and that resulted in a Zero phosphate reading from my Sera test.

The reason I stopped back flushing was because I always got a 0 reading on my TDI meter regardless of back flushing. Even before I changed all the filter units in the spring I always had a 0 reading on my TDI meter (Milwauke brand)

So, I guess I learned something new. TDI meters don't include phosphates.

AquaAddict
PS I have been using Fozdown with considerable success
PS Maybe my phosphates are high because of the long spring and summer drought?