3m is ok. same things could happen at 3.5m.

When we see green water, we humans tend to think of algae or mould - it's hard to change that way of thinking. A pale , sandy pebblecrete will look like a sandy lagoon, whereas a blue will be more eye-catching. We replaced the second liner of our pool with blue tiles . It's quite a large pool, so we went for a dark blue, I still love the colour nearly ten years later.

watchedpoppy, here's something about heat pumps designed for cold temperatures. Note, these are reverse cycled air conditioners (air-to-air), not pool heat pumps (air-to-water). I don't know how heat pumps stack up. It's an American site, so FYI -13F equals -25C. http://www.mitsubishicomfort.com/benefits/hyper-heating On a side note, temperature is just the product of the motion of atoms & molecules (kinetic energy). These are in motion all the way down to zero Kelvin (-273C). So although it may feel cold outside, there's still energy available in the site, although heat pumps do become much less efficient when it's cold (the difference in input & output temperatures is important). One thing that has made heat pumps very inefficient in the past is that the condensing coil would ice up at around zero C. This would have to be thawed out with a plain old electric element (COP of 1). Greatly reducing the overall COP in temperatures around our below zero C. But the modern heat pumps, which use the CO2 compressors Luxury Home Heating has talked about don't have an electric element to thaw them out, greatly increasing their efficiency. As for the noise issues. Some modern heat pumps (but not all) are very quiet. So just pay close attention to the decibels they produce, listed on their spec sheets. FYI, here's a good read. Though it doesn't mention solar PV, which would be advantageous for a heat pump. https://www.pooledenergy.com/blog/choosing-a-pool-heater-what-are-the-relative-performances-of-solar-gas-electric-pool-heaters/

We have 600x400x30mm limestone pavers and would like to replace our old clay pavers with a more modern look. Question: Can a 400mm wide paver sit on top of a 350mm wide pool coping bed? The coping bed is raised about 150mm above the soil. About 20mm of the paver will go over into the pool side as an edge, 350mm lay on the coping bed, leaving 30mm hanging over, well, nothing. The limestone pavers are dense, heavy, 30mm thick. Question : do you think they will crack or break? Is it do-able or should we cut down the pavers to 350mm width (extra cost). Appreciate your advice Houzzers.