Connecting hot tub to OWB

[jbphan8]

Hi all. Found lots of helpful info here in the past and hoping to get some more. I have a Central Boiler OWB that heats the house, garage, and hot water. Looking to tap into the system to also heat hot tub. CB has diagrams of how to do so and I (with my plumber) am fairly comfortable with the install. My question surrounds the pipe used to run the hot tub water (and its chemical component) to the heat exchange plate. I am using PEX to run the OWB water to the plate and had planned on also using PEX to get the hot tub water to the plate. My plumber noticed on the CB diagram that they show PVC as being used on the hot tub side of the plate. He also had thoughts of copper and brass instead of PEX to get to the plate but questioned both after seeing the diagram. We both suspect that it is pictured as is (without PEX) for a reason and are concerned that the chemically altered hot tub water would cause issues with the copper/brass and PEX. The plate itself is SS so we think we're good there. Called the hot tub company and they have not had anyone do this that they know of. Also waiting on info back from CB. Thought you all might have some ideas. Actually, I know you will. I know I have seen threads before about similar attempts so hoping to learn from others as to what will work and I guess even moreso, what won't. Thanks in advance.

JD

 

[webie]

Here is a good thread for which I think you should read ,,,,,,,,,,,,
Its my upcomeing summer project .
https://www.hearth.com/econtent/index.php/forums/viewthread/50202/

 

[Gooserider]

Do a search, I think you will find lots of discussion on the subject, as quite a few people have done it...

I don't know the "official" reasons, but what I suspect is that the big reason is to avoid issues with the hot tub chemistry... PEX can have problems with some of the chemicals in pool / spa water (including the petrochemicals in some body lotions and the like, and I think there may be some issues w/ chlorine. etc) Iron will have MAJOR problems with pool chemicals and especially the large amount of oxygen in hot tub water, and copper can have issues if the chemistry isn't just right.... OTOH, PVC is pretty much inert, and isn't bothered by anything that you'll have in the tub. There is a reason why it's the generally preferred material for pool and spa plumbing...

Gooserider

 

[jpowell1979]

This is how I did mine. I used pex underground and PVC to the heat exchanger. Any copper will be corroded rapidly by the chlorine so you want to use only stainless or PVC for anything that will be in contact with the spa water all the time.

 

[mpilihp]

Hi AlaskaWoodburner Im trying to hook my hot tub up to our wood boiler as well. Was looking at doing something different but I think the need to stay away from steel/copper lines will prevent that.

Can you tell me where you put the aqustat? And Im assuming your using the aqustat to tell the boiler side pump to run?? If not can you explain that part?

My other question is how exactly did you connect it to the hot tub, I know you said you hooked it to a drain and the return line to a line for an air intake for the jets. Water flow wise does this mean water is circulating through your tub side HX loop independant of the existing pump plumbing?

When the pump runs does it cause any back flow??

Thanks ~ Phil