If an open system is plumbed properly the water will only be as stagnant as all of the other domestic hot water in the potable system, rendering it as safe as safe can get. To do this, the incomong water service must first circulate through the radiant tubing before getting to the hot water source. Every time domestic hot water is called for (opening of a hot faucet), the entire radiant heating system gets flushed out. The water will only be as stagnant as every other hot water pipe in the system (or even less so if a faucet location is not used very often). A back-flow valve must be used just upstream of where the source water enters so that the incoming water flows forward. One might argue that the incoming water cools the system - in terms of the whole system though, there is only a temporary transfer of heat from the floor back to the heat source, but it really shouldn't be thought of as cooling, except during the non-heating season. The entire system retains pretty much the the same amount of heat (losses would be only with the transfer through the conduits). The benefit of open direct system is that it is more efficent because there is no heat exchanger. The floor cooling in summer is also a nice benefit. Two things to check: must use all potable equipment including pumps, expansion tanks, everything; and, check with your local code enforcement folks - some places don't allow open direct. The typical reason that they don't allow it is fear that non-potable equipment might be installed during repair or other maintenance work (that would be a real concern - an open direct system should be clearly identified as such so that anyone working on it is aware). I'm a fan of open direct and I think the health threat is a non-issue as long as the system is done right.

I've done many hundreds of pools with flagstone under the water. You'll actually find in a salt water pool that the rock underwater does better than the rock above the waterline. On the chillers I've never done the Glacier brand coolers. I'm also in the Houston area and have had great luck with the gas defrosting heat pumps which can chill in the summer or heat more affordable in the winter than natural gas or propane. I have 2 of them on my pool which are running right now. I use them to bring on the swim season a little early and then maintain the swim temp (mid 80's) from Halloween to the first of December. I've only used the chillers every now and then during the summer, last summer was one of the times. My pool is very large and does a decent job of keeping reasonably cool water in the summertime. On an average pool size in SE Texas I'd definitely have one. I haven't priced a Glacier but would assume it to come in at less than half the price of a heater/chiller. I'll look this evening and get you some pic's of all flagstone beaches and steps/benches with flagstone. See ya, Kelly

Eskimopie, we just finished our pool in Tucson! Just found the forum though, wish I would have found it sooner. ItÂs been a bumpy 5 months. Anyways, our take on the SWG here in Tucson- we opted not to install. Too expensive and from our neighbors accounts more maintenance than they were sold on. SWG will have major PH and alkalinity issues and need to run the pumps for extended times due to our summer heat. Chlorine pucks for us, IÂve added 2 to the skimmer, easy compared to pouring acid every couple days. Our PB said red eyes are a PH issue not a chlorine issue. HavenÂt heard of the FROG. Good Luck

Hi racket, Yes in the new england climate we really can only use the pool from April (if we are really lucky) through September. The problem is that temperatures in April can be in the 40s overnight or lower even though they may reach lower to upper 70s during the day. I don't know if this is really enough ambient heat to make the heat pump function well. That being said if the operating cost for an electric heat pump really is a lot lower (presumably the heat pump would need to be operating continuously whereas the gas heater could be turned on say 24 hours before you plan to use it or kept on all the time) then perhaps it is worth it in the long run. Certainly the initial cost is probably actually lower given the potential cost of the gas line installation. Thank you for your thoughts!