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http://markurban.com/flowReversal.html
The above site has some sort of valve that lets you (or so it claims) more effectively heat your pool. What it does is extract water from the skimmers and returns (yes the returns) and returns the heated water via the main drain. Seems kind of strange. Has anyone heard of this, if so does it work?
It doesn't make any sense to me. If you have good circulation all the water is the same temp anyway. And honestly if it is colder down by your feet with poor circulation it's saving you money if you heated all that water it would take more heat, which in a pool with good circulation it does anyway.
The theory of the flow reversal will work but pool return inlets are not made to be suction inlets. In an existing pool you could get the same effect by pulling all your water thru the skimmers and returning the water to the return inlets pointed towards the bottom of the pool floor. It is more efficient from a heating stand point to have the hot water return into the pool from the floor because as heat rises it will heat more water. The best way to do this is to have an infloor cleaning system that returns hot water to the cleaning heads.
Sure, it sounds good, but the authors have forgotten a few things:
1) Water rising from heat is called "Convection" but is only one of 3 ways heat is transmitted. The other two are "Conduction" and "Radiation". They are all equally important.
2) Cleaning the pool IS more important than heating it--sanitation is critical. But as someone else pointed out, the circulation is very powerful and mixes the water very rapidly. While boiling a pot of water makes the most sense to heat it from the bottom, if you have a mixer going, then heating it from any direction should be about the same.
3) I solar-heat and circulate my water all the time and the bottom of the pool is rarely much cooler than the higher water. I don't have a "thermocline", which thein author's system pre-supposes.
4) When using a CLEAR solar cover, sunlight penetrates all the way to the bottom of the pool, heating from the bottom as well.
5) The claims of energy efficiency are MEANINGLESS to a person with effective solar heating. My heat is already free--if my pool is warm enough, why do I need to increase that.
6) The increased efficiency claim is undocumented.
Biggest drawbacks to reverse flow systems is that they usually require automated valves to change the flow pattern to reverse for heating and normal for effecient cleaning and filtering. IMHO, they are not worth the expense for a possible slight increase in heating efficiency. If the pool is already plumbed with an in floor cleaner it will accomplish basically the same thing but I don't think much of in floor cleaners either because of the strain the place on the plumbing system
Expanding on what I had said above, it can't be more efficient. Heating 20,000 gallons of water will take x number BTU's no matter if you heat it from the bottom or middle to side or top. Heat is heat.
Actually your heater itself will be more efficient as the temperature of the incoming water is lower. So let’s just say you do have a thermocline in your pool and it is 85F at the top and 80F at the bottom. If you heat that 80F water it will extract more heat as it passes through the heater then it would if it were entering at 85F. Of course if you increase the flow though the heater as well you would extract more heat.
Again to heat a 84F pool to 85F it won’t matter where the heat enters, from the sun, a bit from the air or from a heater. As long as it is properly circulated it will take the same amount of heat to heat it up.