Chlorinator loop with heater

[riny]

Hey all, I'm thinking about adding a Hayward H150FDN gas heater. I'm looking at the plumbing diagram in the Hayward manual (page 26, copied below) for installing a chlorinator (SWG in this case) after the heater. I'm 100% good with the solid-line part of this diagram but I don't understand the "optional (preferred)" hookup. It says "preferred" but it's not discussed anywhere in the text.

It looks like this runs the chlorinator on a separate loop that bypasses the heater. This doesn't make sense to me though. It tees off after the pump but before the filter. This means the pump will be pushing unfiltered/unheated water back into the pool. I imagine the resistance on this path will be much lower so you might not get much flow through the filter/heater at all.

What am I missing, and why is this "preferred" anyway? Can I just ignore the dotted-line part and do it the other way?

Also I'll tack on a related question: the heater inlet/outlet are sized for 2" or 2 1/2" pipe, but all of my existing lines are 1 1/2". Is it ok to just reduce from 2" to 1 1/2" at the heater nipples? Do you recommend buffering with any length of 2" pipe before/after the heater?

 

[ajw22]

You have to consider that when diagram was drawn SWGs were not popular or barely existed and “chlorinator” referred to tablet chlorinator feeders.

Basically that diagram does not apply to a SWG. A SWG does not have acidic properties and you do not need a CV between it and the heater. You do not need to protect the heater from the SWG.

Just reduce the 2” heater output to 1 1/2” coming coming out of the heater.

 

[Jimrahbe]

R,

Most SWCG's are 2", so I would come out of the heater at 2" and then through the SWCG and then reduce just before going back to your 1.5" return lines..

Reducing to 1.5" will not cause you any issues.

+1 on what Allen says about not needing a check valve if using a SWCG.

Thanks,

Jim R.

 

[riny]

Aww, well @Dirk sold me on the FlowVis, combination flow meter & check valve. I might get one anyway because they're cool, and claim to be more reliable than the stick-in flow meters, if you believe the marketing.

Thanks for the advice otherwise. Out of curiosity, even with a tablet chlorinator, wouldn't that loop still be a problem? I'm failing to see how the dotted-line segment could ever make sense.

 

[ajw22]

Out of curiosity, even with a tablet chlorinator, wouldn't that loop still be a problem? I'm failing to see how the dotted-line segment could ever make sense.

It will work. Half your water flow will be heated and half will be chlorinated. The amount of heat added to the water is fixed by the BTU output of the heater regardless of flow. The heated water and the chlorianted water will then be combined and mixed and flow into the pool.

You would need to run your pump at a higher RPM to have adequate flow on both legs, but that picture was drawn in the days of only single speed pumps. It really does not work well the way we now run energy efficient VS pumps.

 

[riny]

Ah, makes sense, thanks.

 

[Dirk]

If you decide to install a FlowVis, be sure it does not compromise the flow sensor of the SWG. I suppose that will be brand dependent. My SWG, for example, requires a straight, uninterrupted length of pipe before the inlet, because its flow sensor is inside, and turbulent flow entering the SWG will mess with the flow sensor reading. A check valve, including the FlowVis, has a spring loaded flap by which the water will pass, and that flap can compromise the flow. So I wouldn't want my FlowVis a few inches away from my SWG. Check the installation manual of the SWG you choose for any similar requirement.

Flow is constant throughout pool plumbing. There are exceptions to that principal, especially if you have a bypass like your illustration suggests, but generally, flow through a single run of pipes will be the same at any given point. That includes if the pipe changes diameter. The velocity of the water through different sized pipes would be different, but the flow, the amount of water entering one end and existing the other, will be the same.

Which means: you can install a FlowVis anywhere and it will give you the same flow reading. As Jim and Allen point out, you don't need the check valve function of the FlowVis to protect your heater, so it doesn't have to go there. It can, if there is enough pipe between it and the SWG's flow switch, but it doesn't have to. It can go between filter and heater. Mine is between pump and filter.

For those that can't wrap their head around "flow is constant, but velocity can vary:" FlowVis accomplishes its ±2% accuracy by providing different models for different sized pipes. So it's important you get the right size. Mine works on 2" pipe and 2.5" pipe, because it has two different scales printed on it. I use the 2" scale. If you plan on putting the FlowVis on a 1.5" section of pipe, you need to order the model for that pipe size.