Heater Install

Jul 7, 2008
54
Bremen, GA
Hi everyone.....thanks for all of the teachings and advice that is given on this fourm.

When I pool was being built, I asked the PB to add a couple of valves for a future heater. One for the inlet and the other for the return. I've noticed on several pools that the SWG is installed after the heater. My SWG is located before the heater setup. Is this a problem? I have plenty of room if I need to move the SWG further down, after the heater. Do I need to relocate my SWG?

Thanks...David

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It would be a good idea to place the SWG after the heater. A SWG produces chlorine, which can be corrosive to metals at sufficiently high levels. With the SWG before the heater it is possible for chlorine levels at the heater to be high enough to cause corrosion under certain circumstances. There is also a risk of hydrogen gas from the SWG building up in the heater, if the SWG comes before the heater, which could potentially lead to an explosion. While these situations are normally fairly rare, it is better not to take that chance with your heater.
 
Interesting... My sister has a SWG after the heater on her pool and the salt cell started leaking before it was even 3 years old. It appeared that the O-rings that seal around the electrical contacts had baked out and cracked and I just figured it was the heat from the heater causing the problem. I think it's a Zodiac brand, IIRC. Seemed to me that it would live longer on the cold water side of the heater. Does it really create enough chlorine to cause corrosion problems? I thought that they added very little chlorine, but over a long period of time, so that the actual chlorine levels in the line would be somewhat low. Now I'm all confused... :? :? :?
 
The situations that allow chlorine to build up to dangerous levels are quite rare, but it is difficult to be sure they will never happen. The most common way would be for the SWG to be on while the pump is off. Normally there is a flow switch preventing that, but flow switches are prone to failure.

Also, depending on a number of factors, it is possible to have a situations where a very large SWG produces chlorine quickly and the pump is run on a very low speed, resulting in high chlorine levels even though the pump is running. This case becomes more likely as the CYA level goes down, since damage can occur at lower chlorine levels when the CYA level is lower.

If the SWG is mounted after the heater, but is too close to the heater, you can have damage such as HarryH3 describes. This is easier to prevent, since it normally only takes about three feet of pipe to avoid a problem. In this case the primary risk is from residual heat in the heater after the pump turns off. Some heaters have much more residual heat than others.

There is also a small risk of water flowing backwards with the pump off and drawing chlorine back into the heater. Some people use a check valve between the heater and the SWG to prevent this, though again there is hardly ever a problem even without the check valve as long as there is enough pipe between the heater and the SWG.
 
I hope all goes well. The four major SWG companies (Autopilot, Goldline, Jandy and Zodiac) all picture the installation of the cell downstream of ALL equipment, including the heater. As outlined by someone above, the gas generation could be a hazard, but the possibility of damaging the expensive heat exchanger in the heater is paramount. :)
 
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