Bypass Valve On Heater

[thepoolman1]

If you are going to do this, make sure to drain the heat exchanger when the water is not in circulation through the heater. You will have deposits left on the inside of the tubes when the water evaporates if you do not. They will build up, at times to the point of blocking the tubes nearly closed. If your system is not capable of of moving the maximum water flow, I would only put the bypass in case of there a problem with the heat exchanger. This is very rare if you maintain good water balance. Also, it is good to fire a heater at least once a month (once a week is better) for about 5 minutes to make sure it works and to help keep out the "critters."

The reality is that this is a lot of extra work and expense for very little return, unless it gives you peace of mind. If you are going to do this, make sure that you use valves made of CPVC (like Pentair, Hayward, or Jandy) so that there is less likely to be heat damage to the body.

[Poconos]

When I had my heater I did do the plumbing to be able to bypass the heater only to cut the flow resistance when the heater wasn't being used. As for using CPVC, I don't think that is necessary. In any heater operation situation I can't see any way the water temperature in the pipes can be anywhere near the softening point of plain PVC. I admit I can't remember what the recommended temperature limit for PVC is but it is way above what any water in the system should be. Please correct me if I'm wrong or missing something.
Al

[jrv331]

Thanks for all the help. I'm using Pentair 3 way valves for the bypass. I Mostly want to be able to avoid running water through the heater when shocking with high levels of bleach or some other chemical.
Thanks
John

[waste]

That's a great idea!! If we're only talking about being able to temporarily by-pass the heater, you won't have to worry about draining the heater when it's being bypassed. If you (or anyone else who can by-pass their heater) ever decide that you want to by-pass the heater for longer than ~ a couple of weeks - be sure to drain the heater, as per thepoolman1's suggestion

[thepoolman1]

Regular PVC does tend to start to soften above 90 degrees. If a spa is being heated, the water will regularly be above 100 degrees. Since there are so many different Mini-Max models, some with bulkhead fittings, some with cast metal headers, a good recommendation is to use a short section of CPVC on the inlet and outlet ports. I always do this on my heater installations and have never had an issue with the connections directly at the heater unless there is a malfunction in the heater itself. A couple of short pieces of CPVC (6"-12") does not cost much and is, in my opinion, worth the extra cost and effort.

Unless you have a "fireman's" switch on your timer (for heating a pool) or an auto control with a cool-down cycle, most people will not cool their heaters properly after using them, especially with spa use. Even the retained heat in a newer heater and plumbing will eventually warp the systems plumbing if not cooled. Heater manufacturers say that proper cool-down can add 50% to the life of a pool/spa heater.

Just Thursday had to re-plumb a system that was only 4 years old but had very regular spa use. It is a manually-controlled system and the customer said he was never told about cooling the system before shutting the pump down

Just my experience.

[mas985]

Here are one set of pressure deratings for both PVC and CPVC. 2" schedule 40 PVC has a rating of 200 PSI at 110 deg F which much more than what is needed for a typical pool system.

It is true that PVC is more easily deformed at higher temperatures but according to this reference, PVC really doesn't start to significantly soften until 54 degrees C or 129 degrees F and that is with a lot of loading. The derating for pressure drops much sooner but the rigidity isn't affected as quickly unless of course there is a large load on the pipe but given the short sections of pipe, it is unlikely that the pipe would ever sag.

From my personal experience, I have never had a problem with heat deformation of the pipe exiting my heater. I also have had experience bending PVC pipe with a heat gun and you have to get it much hotter than what a heater could do before it even starts to bend.