Bruce Napier <[email protected]> wrote: >On 16 Jan 2009, at 10:19, Adrian Stott wrote: > >> Why would a more complex (i.e. adjustable) one be needed? > >If there is no barrier between the air and the water, the air will >all tiptoe gradually away as it dissolves in the water. Hence there >is usually some sort of diaphragm or bladder to stop that happening.
It is true that air can dissolve in water. However, the rate is fairly slow. Moreover, once the water below the air is saturated with air, little more will dissolve (by definition). Since my accumulator is at the end of pipe cul-de-sac, there is very little water exchange within the pipe. I have never bothered to emtpy the (any) water out of my accumulator in the ~20 years I have owned it, and it still seems to be doing its job just fine. >Because the optimum pressure is either half the pump cut out pressure >or a little less than the cut in pressure (depending who you believe, >and often comes to much the same thing), and because pumps vary in >these pressures, you need to be able to adjust the accumulator pressure. Only if the accumulator has a diaphragm; a good reason not to have this type, perhaps? Another might be that (I suspect) it is more expensive. Adrian . Adrian Stott 07956-299966
