I'll bet that normal pressure is the driving force and that there is no pump because there is no need for one with normal pressure: that is how all other water outlets work (faucets, taps, supply hoses, etc). Inside a 1/4" thin pipe you'll see it is a very small diameter tube in reality. I'll bet a little bit of organic matter has stuck to the inner wall and narrowed the diameter to the point where it has effectively blocked the flow down to a dribble. After ten years this is probable. ((For further evidence that this is probable, search in the plumbing forum for posts about sludge / organic matter in water heaters.) "... water pressure is at 65psi and water is supplied via a 1/4 copper supply that is hooked up to a ball valve (not a saddle clamp)." If you buy my hypothesis, to test it out and clean out the supply line is actually quite easy (Once you turn off the whole house water and drain your pipes which is the big upheaval in your daily routine.) Post this question in the plumbing forum. -david

good one racket! poolguynj - sorry, didn't mean to confuse the uninitiated. This topic has been hashed out in lots of detail on this forum in the past. There is some good stuff related to this topic if you search for it. Pentair has posted some real world field test data taken over a few weeks time comparing variable speed to 2 speed technologies. The differences are not as great as you suggest and depend largely on the speeds the pumps are used and the length of time at each speed. Didn't mean to hijack....just thought that UK should know the biggest contributor to power consumption with pool pumps is pump speed. Keep the speed low and the power consumption is reduced exponentially regardless of pump technology. This is so important but yet I see variable speed owners on this forum who are running their pumps at higher speeds thinking they are saving money because it's a variable speed pump....not entirely true. The true savings come with low pump speed operation which can be achieved with a variable speed or a 2 speed. Obviously the variable speed has more flexibility than the 2 speed. Take advantage of the variable speed and keep the speeds lower than 1725 rpm whenever possible. This is where the variable speed pumps really have an advantage over 2 speeds. The 2 speeds cannot be designed to go much lower than 1725 rpm without efficiency falling off sharply as you suggested. By the way, I work for a major US company that manufactures variable speed motors and drives as well as standard technology PSC motors with multi-speed capability. I sell these components to the HVAC industry and work with their engineers daily to help meet their performance and efficiency needs. Hope this helps.

I have a similar question, but mine is for our inground gunite pool with DE filter (pool is 18 years old, but we are new owners of the house/pool). We fired the professional company who overcharged us and didn't do the work. Here's our issue now: after multiple backwashes and adding DE, our filter pressure gauge is still reading 1, or zero. I'm assuming from the wonderful posts on this website that we need to get a professional to clean the filter cartridges, but should I turn off the filter until then? It's going to be 92 degrees here in SC today, so I'd rather not turn off, even with the slight trickle flowing in the pool. Thanks!

Just my two cents, on heat transfer in a dynamic environment. I.e. fluid as opposed to a solid block of anything. There is a lot of opposing theory here. First lets try and apples and apples it. If the surface area and thermal dynamic properties of the heat exchanger are the same i.e. one is aluminum a one is copper. And the only variable is the speed at which the water flows through the pipe. You first have to understand the effects of laminar flow on the xsfer of heat (energy) from the walls of the heat exchanger to the fluid in the center of the pipe. Due to the increase of friction at the edges of the water Colum inside the pipe , the water in the center of the pipe flows faster, with me so far? The statement "heat xsfer is greatest when the deference between the bodies is greatest" is in a way correct when you look at percentage of transfer. What you fail to take into account is that the transfer works both ways. At the same time you are heating the water , you are cooling the pipe. Thus requiring more energy to heat the pipe. Since the energy to heat the pipe is limited i.e. the amperage of your wiring in a heat pump or flow of gas in a furnace, You must stick to real world. Another fact is heat transfer has momentum. Once you pass a point of the curve you see a ramping effect called thermal momentum. Soooo if the gauge is how fast you raise a body of water outside the exchanger i.e. a pool or spa the question is simple the longer a molecule is in proximity to a heat source the more energy it will adsorb. So the two options are 1. to run that "piece" of water quickly through the exchanger so it can deposit its heat into the body of water and go back and get more? Or , 2. to allow that "piece" of water more time in the exchanger to gather more energy to deposit it in to the water. The end result is the same, Hot. The deference is the curve. We use this formula every day in controlling chemical reactions through temperature. The slower moving fluid reaches the steeper part of the curve faster, thus gaining Thermal momentum fasterÂ.. ending up with the body of water reaching a desired temperature faster. DamÂ.. I need a beer!