Conventional Wisdom re SWCG plumbing placement

[TishTash]

It’s a foregone matter-of-fact that the inline chlorinator should be the final leg of plumbing before going to the return back into the pool, i.e., skimmer/drain -> pump -> filter -> heater -> SWCG -> return. My installer (back in 2017) wasn’t the brightest bulb in the shed, and ran the pipes to and from the heater underground and within the coping walls to the return. The only extended piece of exposed plumbing is between the filter and the ground (presumably tunneling to the heater).

I currently use an offline chlorinator that’s been more than satisfactory for my not-so-giant pool’s needs (plus it’s not dependent on a minimal flow rate to function). However, should I finally decide to get the more typical in-line SWCG, is it that lethal for the heater to be downflow of it? I say that because of the importance placed on there being a check valve upflow of the SWCG, I assume to keep any of the generated chlorine wafting backward. Is any of this in any quantity that poisonous to the heater?

 

[PoolStored]

Your post is a bit confusing...what is an "offline chlorinator?"

There is no case where I would install a puck chlorinator after a pool heater (even with a check valve). Full stop. A puck chlorinator will kill a heater post haste...

If you install an SWG after a heater, and install the SWG in such a manner that the SWG cannot run without the pump running (timer or current sensing relay), there should be no issue.

 

[TishTash]

Sorry for the confusion. Forget the offline SWCG; that’s a macguffin in my post.

By “chlorinator” I meant an inline SWCG and only an SWCG.
(But I see where it implies a puck chlorinator; it’s not that.)

The typical setup is to have the plumbing flow from the heater to the SWCG to the pool return (at least that’s what I’ve always been told). A point is also made to have a check valve before the chlorinator, which I always presumed was to keep the freshly generated chlorine away from the heater.

In my setup, the SWCG can only be installed before the heater, and I’ve always been told one can’t do that. Just how true is this implication that a heater can’t be subject to newly SWCG-chlorinated water?

 

[jonpcar]

@TishTash, Here is your previous thread which attempts to address this same issue…there are pictures there but they are poor and taken at night (you need better ones for help). In addition, your comment in this particular post (#4) about the heater being to the left of the generator seems to be in error?

Fix for plumbing mixup

Wouldn't you know it, but the pool installer put my now-unused Frog device between the filter/pump and the heater, which then goes straight to the eyeball inlet return. After a couple years of futile use, the heater is ok, despite it being fed dichlor/trichlor/minerals/snake-oil, when it should...

www.troublefreepool.com

I don’t know that you will get agreement to put your proposed, new SWG before your heater. The right way is to follow and expose (dig up) the output from the heater (somewhere) and extend it so that the SWG can be installed. Unfortunately, you will have to be careful of the electrical which seems to be located near the heater’s input/output pipes.

It may also be possible to simply “move” the heater to get access to its plumbing by pushing the heater around on its pad or extending its pad.

 

[Jimrahbe]

Just how true is this implication that a heater can’t be subject to newly SWCG-chlorinated water?

TT,

I tend to agree... If you are running an FC of say 7 or 8, that will be flowing through the heater at some point anyway..

Let's ask someone that have a much better chemical background than me.. Calling @JamesW .. Why would a SWCG connected to the heater input be a bad idea???

Thanks,

Jim R.

 

[HermanTX]

A couple of things to consider
The inline FROG chlorinator you had located upstream of the heater is much more damaging to the heater because of the acid in the pucks. A check valve is recommend before any inline puck chlorinator to prevent back flow into the equipment, especially when the pump is off.

If your only option is to place a SWCG upstream of a heater then there is less risk of damage because a SWCG does not produce acid. Also, a SWCG only operates when the pump is on - you have to ensure you set it up properly that it turns on and off with the pump. Therefore, there is no need for a check valve when using a SWCG (when the SWCG is placed downstream of a heater).

Ideally you want to mitigate the risk and move the SWCG to be downstream of the heater. You do not show any pictures if that is even feasible or if it is, is it a costly undertaking.

 

[JamesW]

You don't want to expose the heater to chlorine gas or hydrogen gas or have anywhere that either gas could potentially accumulate.

I don't know how much risk there is with good water flow.

Chlorine gas dissolves pretty quickly and copper is not especially susceptible to hydrogen attack.

Most likely, the risk is low, but I would not put a SWG Cell before the heater.

Most manuals say to put the cell last after all other equipment.

If the cell is before the heater, the heater manufacturer could use it as a reason to void the warranty.

 

[JamesW]

Hydrogen embrittlement occurs in steels, as well as in iron, nickel, titanium, cobalt, and their alloys.

Copper, aluminium, and stainless steels are less susceptible to hydrogen embrittlement.

A heat pump uses titanium.

Most likely, the SWG cell before the heater is probably low risk, but I would not do it.

 

[JamesW]

See what Hayward has to say.

Contact Us

hayward.com

 

[ajw22]

Show us good pictures of your Hayward heat pump.

The output pipe has to be exposed before it goes underground. I would think you can tap in an SWG at the heater output.

 

[Jimrahbe]

TT,

Show us several pics of your equipment pad and maybe we can come up with some better ideas...

Thanks,

Jim R.

 

[hexabc]

TT,

I tend to agree... If you are running an FC of say 7 or 8, that will be flowing through the heater at some point anyway..

Let's ask someone that have a much better chemical background than me.. Calling @JamesW .. Why would a SWCG connected to the heater input be a bad idea???

Thanks,

Jim R.

What's the chlorine contents right after SWCG when the target is set to 7 or 8 ? Is it close to the target or rather much higher, something like 15?

 

[JamesW]

It depends on the cell production rate and the flow in GPM.

At 20 GPM and 2 lbs production per day, the FC is increased by 8.3 ppm from inlet to outlet.

If you have 8 ppm before the cell, then you have 16.3 ppm after the cell.

Also, not all of that is combined with CYA because that takes time.

 

[Jimrahbe]

What's the chlorine contents right after SWCG when the target is set to 7 or 8 ? Is it close to the target or rather much higher, something like 15?

Hex,

To be honest, I have no clue... Kind of why I asked JamesW...

I 'assume' is it not really very high at all, and that is why you have to run the SWCG for a long time to bring your FC up..

My original point is that I don't think chlorine is an issue... And if you read JamesW posts above it appears that the main problem is with the chlorine gas or hydrogen gas collecting somewhere in the heater...

My recommendation would be to have the SWCG after the heater, but that is just because that is what everyone says to do, but I don't see many facts about why and what damage would actually happen if the SWCG was installed before the heater.

Thanks,

Jim R.

 

[Newdude]

IMO it would take me way longer to work enough hours to buy a new heater than it would to protect my $6k(?) investment. Like. A couple work weeks worth of hours, verses a slightly annoying afternoon.

And that's on top of my regular work hours because those funds are already budgeted to living expenses.

 

[Newdude]

Also think of gifting them an easy out of the heater warranty. I could see them saying 'See ? This is why we prefer the SWG after the heater. Claim denied' for something unrelated like the circuit board.

 

[hexabc]

It depends on the cell production rate and the flow in GPM.

At 20 GPM and 2 lbs production per day, the FC is increased by 8.3 ppm from inlet to outlet.

If you have 8 ppm before the cell, then you have 16.3 ppm after the cell.

Also, not all of that is combined with CYA because that takes time.

It's a good point about CYA - the water leaving SWCG is probably much more aggressive (oxidizing) than what the target FC and the CYA level would suggest.

 

[TishTash]

@TishTash, Here is your previous thread which attempts to address this same issue…

Fix for plumbing mixup

Wouldn't you know it, but the pool installer put my now-unused Frog device between the filter/pump and the heater, which then goes straight to the eyeball inlet return. After a couple years of futile use, the heater is ok, despite it being fed dichlor/trichlor/minerals/snake-oil, when it should...

www.troublefreepool.com

Wow, thanks for digging that up; my posting of that completely slipped my mind.

there are pictures there but they are poor and taken at night (you need better ones for help). In addition, your comment in this particular post (#4) about the heater being to the left of the generator seems to be in error?

I was referring to the reverse angle photo, from behind the heater, showing its input and output plumbing as requested. From the front, the heater is to the right of the generator.

I don’t know that you will get agreement to put your proposed, new SWG before your heater. The right way is to follow and expose (dig up) the output from the heater (somewhere) and extend it so that the SWG can be installed. Unfortunately, you will have to be careful of the electrical which seems to be located near the heater’s input/output pipes.

What you describe is the right way, absolutely. As mentioned, it’s the only way described by everyone it seems.

It may also be possible to simply “move” the heater to get access to its plumbing by pushing the heater around on its pad or extending its pad.

Yeah, that’s actually an innovative thought, but executing that given the layout of the patio would drive my spouse to homocide.

 

[TishTash]

The inline FROG chlorinator you had located upstream of the heater is much more damaging to the heater because of the acid in the pucks. A check valve is recommend before any inline puck chlorinator to prevent back flow into the equipment, especially when the pump is off.

Thanks for bringing this up: I’m sure the brief time I ran the FROG didn’t exactly benefit the heater. (Dang you TFP for not letting me discover you earlier!)

If your only option is to place a SWCG upstream of a heater then there is less risk of damage because a SWCG does not produce acid. Also, a SWCG only operates when the pump is on: You have to ensure you set it up properly that it turns on and off with the pump. Therefore, there is no need for a check valve when using a SWCG (when the SWCG is placed downstream of a heater).

I stand corrected. I read somewhere that a check valve upwind of an SWCG was essential, but exactly how much of a residual backwash actually happens when the pump is off can’t be enough to cause damage, I would think.

(Ah, here it is. Apparently, the “need” for an SWCG check-valve is an archaic remnant of requiring one on (much more acidic) tab feeders.)

Ideally you want to mitigate the risk and move the SWCG to be downstream of the heater. You do not show any pictures if that is even feasible or if it is, is it a costly undertaking.

Show us good pictures of your Hayward heat pump. The output pipe has to be exposed before it goes underground. I would think you can tap in an SWG at the heater output.

Show us several pics of your equipment pad and maybe we can come up with some better ideas...

Sorry about the dark photos from the previous thread referenced by @jonpcar; here are better ones below (in daylight! how quaint). The 1st photo is sans pump and filter (because it’s winter). The pipe going into the ground goes to the heater, whose output goes underground and inside the brick wall to the skimmer. I suppose the output could be extricated and plumbed with new exposed pipe to when it went into the brick wall, allowing the SWCG to be placed there, but as you imply, I’d have to weigh the cost and trouble of that.

 

[TishTash]

You don't want to expose the heater to chlorine gas or hydrogen gas or have anywhere that either gas could potentially accumulate. I don't know how much risk there is with good water flow. Chlorine gas dissolves pretty quickly and copper is not especially susceptible to hydrogen attack. Most likely, the risk is low, but I would not put a SWG Cell before the heater. Most manuals say to put the cell last after all other equipment. If the cell is before the heater, the heater manufacturer could use it as a reason to void the warranty.

Also think of gifting them an easy out of the heater warranty. I could see them saying 'See? This is why we prefer the SWG after the heater. Claim denied' for something unrelated like the circuit board.

Thanks @JamesW for all the footwork in posting those excerpts from manuals. Intuitively, I’d agree the exposure of chlorine gas would be minimal with decent flow. That said, you & @Newdude are not wrong to argue a manufacturer would use any excuse to avoid warranty coverage.

Interestingly, Intellichlor says “always” install the SWCG after the heater, while Hayward and Jandy use “preferred” as the qualifier. One implies compulsion; the other suggestion.

See what Hayward has to say.

Contact Us

hayward.com

Funny thing: I actually did. The guy I got in customer service (who couldn’t let it be known any clearer he was not in the mood for questions) basically read me the text from one of the pages you posted.