Is a Hartford loop a good substitute for a heater check valve?

[OWSwimmer]

My new 18000 gallon in ground pool was installed with a Pentair 400k heater. A Pentair “positive seal non corrosive Check Valve” was not installed per the installation manual recommendation. Instead a rather short “Hartford Loop” was installed. I understand it’s important to not let water siphon into the heater when the pump shuts down so I am considering installing a check valve if it is a better option.
Does anyone know or have an opinion about the functionality of a “short” Hartford Loop vs a backflow preventing heater check valve?
Thanks in advance and I’ll try to attach a picture of the heater and plumbing.

 

[ajw22]

You are fine with that piping. You don”t need a CV between a SWG and the heater in spite of what Pentair says.

You do have a CV between your tablet chlorinator and your SWG cell which you will need if you ever put tablets in it.

A SWG cell does not create acidic water when the pump is off. A tablet chlorinator will create acidic water when the pump is off that will backflow into your pool equipment. Really you should never use that tablet chlorinator. If you need to use tablets in your pool put them in a floater.

 

[generessler]

I am not an expert, but have done some numbers and concluded that a check valve is cheap insurance.

Here is the worst case: If you have a high output SWG cell, say ~4 pounds per 24 hours, and a VSP running at lowest possible speed, say 30 gpm, then the cell is adding about 11 ppm of chlorine whenever it's on: (4 lb/day / 24 hr/day / 60 min/hr) lb Cl/min / (8 lb/gal * 30 gal/min) lb H2O/min * 10^6. Result units are lb CL per million lb water. Plus whatever the base Cl level is. Say 6, so 17 ppm of chlorine in all.

High chlorine is not good for copper pipes like the heater core. All it takes is a gallon or two of backflow as/after the pump turns off to pull this 17 ppm into the heater where it sits until the pump is on again. For one, Swimming Pool Steve is unequivocal that this happens in many pools. For completeness, several folks here have been skeptical of SS's statements. I'm on the fence. He professes to be a builder/maintainer for decades. I believe him. He has nothing much to gain by misleading us. Nearly all he says agrees with TFP.

Will the "Hartford loop" prevent back flow? If there's a siphon at work, then no. But it's got to be very system dependent. In the end, you can be absolutely sure that a CV will.

All the above could be wrong. But the CV will still be a good idea if something does go bad in the heater. In this video



SS points out that oems use lack of a check valve to wiggle out of warranty service. Pentaire shows one in their install diagrams.

As I said, cheap insurance.

 

[JamesW]

The manual says that a check valve is required when a “chlorinator” is used, but in a different section, they say “chemical feeder”.

A SWG is a generator and not a feeder.

You can argue that a SWG is a “chlorinator”, so it is somewhat ambiguous.

In my opinion, the manual is referring to a tab feeder and not a SWG.

When using a chlorinator, install it downstream from the heater and at a lower level than the heater outlet.

Install a corrosion resistant positive seal “Check Valve”, (P/N R172288), between the heater and the chlorinator to prevent concentrated chemicals from back-siphoning into the heater.

Exercise care when installing chemical feeders so as to not allow back siphoning of chemical into the heater, filters or pump.

When chemical feeders are installed in the circulation of the piping system, make sure the feeder outlet line is downstream of the heater, and is equipped with a positive seal noncorrosive “Check Valve”, (P/N R172288), between the feeder and heater.

https://www.pentair.com/content/dam/extranet/nam/pentair-pool/residential/heaters/mastertemp/manual/Manual-MasterTemp-472592-English.pdf

 

[JamesW]

If you have a high output SWG cell, say ~4 pounds per 24 hours

The IC60 is 2 lbs per day.

I don't think that any residential SWG will do 4 lbs per day.

 

[JamesW]

The Aquacal Heat pump recommends a Hartford loop for a tab feeder but there are no requirements or recommendations for a SWG.

For a tab feeder, you really need a corrosion resistant check valve to protect a heater as a Hartford loop really won't prevent backflow of corrosive chlorine from a tab feeder when the pump is off.

I would never have tabs in a tab feeder with the pump off.

The second the pump turns off, the liquid in the feeder begins to migrate out from the feeder and it will destroy everything it touches.

Tab feeder liquid is very acidic and it is a very strong oxidizer, which is an especially corrosive combination far more corrosive than acid or chlorine by itself.

If a feeder contains tabs, the only way to protect the system is to keep the pump running continuously.

 

[JamesW]

The main issue is if you ever have a warranty claim, Pentair might try to void the warranty or deny coverage based on the lack of a check valve.

To deny a claim based on a lack of a check valve, they would need to prove that the lack of a check valve was responsible for the heater damage.

I would probably have one, but use a regular check valve or a CR2 as a corrosion resistant one is very restrictive.

The “CR2” Back-Flow prevention check valve is completely corrosion resistant, making it the ultimate solution for protecting your expensive Heat Exchangers from the potential damage of inline Chlorinators while also maintaining a Full-Flow circulation system.

"CR2" Corrosion Resistant Check Valves - Magic Plastics, Inc.

ALL PRODUCTS “CR2” CORROSION RESISTANT CHECK VALVES* The "CR2" Back-Flow prevention check valve is completely corrosion resistant, making it the ultimate solution for protecting your expensive Heat Exchangers from the potential damage of inline Chlorinators while also maintaining a Full-Flow...

magicplastics.com

 

[Newdude]

In my opinion, the manual is referring to a tab feeder and not a SWG.

'Install a corrosion resistant positive seal “Check Valve”, (P/N R172288), between the heater and the ***chlorinator*** to prevent concentrated chemicals from back-siphoning into the heater.'

I'd see them arguing that the IChlor60 is a chlorinator. Whether it feeds or generates is a moot point to them, it's chlorinating. It's sure an easy out for the warranty folks no matter which way we see it.

I'm mentally prepared to cut one in if the warranty need ever arises, but not everyone has the DIY skills to do that. (Seriously folks...... pvc is about as easy to learn as it gets). But for the folks wary of tackling it themselves, I reccomend having one installed at the first instance someone is already working at the pad. It will cost very little extra labor at that point and pretty much only be the cost of the parts.

 

[proavia]

Or - just correctly plumb a heater bypass in and get benefits beyond that of just the check valve.

Heater Bypass - Further Reading

www.troublefreepool.com

 

[ajw22]

I am not an expert, but have done some numbers and concluded that a check valve is cheap insurance.

Here is the worst case: If you have a high output SWG cell, say ~4 pounds per 24 hours, and a VSP running at lowest possible speed, say 30 gpm, then the cell is adding about 11 ppm of chlorine whenever it's on: (4 lb/day / 24 hr/day / 60 min/hr) lb Cl/min / (8 lb/gal * 30 gal/min) lb H2O/min * 10^6. Result units are lb CL per million lb water. Plus whatever the base Cl level is. Say 6, so 17 ppm of chlorine in all.

High chlorine is not good for copper pipes like the heater core. All it takes is a gallon or two of backflow as/after the pump turns off to pull this 17 ppm into the heater where it sits until the pump is on again. For one, Swimming Pool Steve is unequivocal that this happens in many pools. For completeness, several folks here have been skeptical of SS's statements. I'm on the fence. He professes to be a builder/maintainer for decades. I believe him. He has nothing much to gain by misleading us. Nearly all he says agrees with TFP.

Will the "Hartford loop" prevent back flow? If there's a siphon at work, then no. But it's got to be very system dependent. In the end, you can be absolutely sure that a CV will.

All the above could be wrong. But the CV will still be a good idea if something does go bad in the heater. In this video



SS points out that oems use lack of a check valve to wiggle out of warranty service. Pentaire shows one in their install diagrams.

As I said, cheap insurance.

I never tell a person not to buy insurance if it makes them comfortable but your rationale is on shaky ground:

• We see the OP has an IntelliChlor cell and the largest IC60 cell generates 2lb/day of chlorine, not 4
• Even if we stipulate that when you turn off the pump there can be a 9 ppm slug of chlorinated water in the 6 inch cell that cell is more than 5X its length away from the heater. And the pipe is going to full with water on both side of the cell. So that small slug of 9 ppm water will get diluted by water on both side of the cell before any of it gets into the heater.
• The FC levels you are worried about getting into the heater are less than SLAM FC levels. If your rationale about "high" chlorine levels damaging a heater were valid then the SLAM process would be damaging heater, which it does not.

It is acid in trichlor tablets that are the problem and the acidic water it creates even when the pump is off.

If you want a CV for "insurance" and to not worry about your warranty claims then by all means put one in your pool. My experience with Pentair warranty claims, and I collected on one for a MasterTemp heat exchanger, is they never asked about that.

 

[OWSwimmer]

My new 18000 gallon in ground pool was installed with a Pentair 400k heater. A Pentair “positive seal non corrosive Check Valve” was not installed per the installation manual recommendation. Instead a rather short “Hartford Loop” was installed. I understand it’s important to not let water siphon into the heater when the pump shuts down so I am considering installing a check valve if it is a better option.
Does anyone know or have an opinion about the functionality of a “short” Hartford Loop vs a backflow preventing heater check valve?
Thanks in advance and I’ll try to attach a picture of the heater and plumbing.

I’m a first time pool owner and just starting to grasp the big picture. I’ve everyone here to thank for that. Thank you so much!
Some of what I’m gathering from the responses are noted below and I welcome any feedback if my understanding is not correct.
-Concentrated chlorine just sitting in a heater is bad. Very bad.
-Not using a tab feeder will help but may not completely prevent this from happening.
-My SWG (Pentair IC20) could possibly be considered a “chlorinator” by Pentair and could possibly void my heater’s warranty if a check valve is not used.
-A SWG or a tab feeder if installed, must be installed downstream of the heater.
-Installing a check valve at the heater intake will prevent water/chlorine from siphoning into the heater.
-Adding an automatic by pass valve could be an option to increase longevity. The automatic bypass valve is known as an “IntelliValve” by Pentair.
-There are no downsides to adding a check or by pass valve other than cost and labor?

 

[ajw22]

-Concentrated chlorine just sitting in a heater is bad. Very bad.

Incorrect.

Your CYA level buffers the chlorine and keeps a very low level of active chlorine.

CYA - Further Reading

www.troublefreepool.com

CYA Chlorine Relationship - Further Reading

www.troublefreepool.com

-Not using a tab feeder will help but may not completely prevent this from happening.

Incorrect.

It is the acid in the tablets that cause the concern.

-My SWG (Pentair IC20) could possibly be considered a “chlorinator” by Pentair and could possibly void my heater’s warranty if a check valve is not used.

Yes. But we have had no firsthand reports of anyone among our 200,000+ members being denied a warranty claim for that reason.

-A SWG or a tab feeder if installed, must be installed downstream of the heater.

Correct.

-Installing a check valve at the heater intake will prevent water/chlorine from siphoning into the heater.

Incorrect.

The CV goes at the heater OUTLET.

-Adding an automatic by pass valve could be an option to increase longevity. The automatic bypass valve is known as an “IntelliValve” by Pentair.

The IntelliValve is just the actuator for the diverter valve used in the bypass.

The MasterTemp Connected Heaters support an automatic heater bypass using an IntelliVlave connected to the socket labelled BP_VLV on the PCBA in the heater. Pentair has the AUTOMATIC BY-PASS VALVE KIT (P/N 462048) FOR MASTERTEMP® AND MAX-E-THERM® POOL AND SPA HEATERS

Pentair says "in conjunction with a Pentair IntelliFlo VF pump the automatic by-pass valve functionality of the latest MasterTemp heater will improve the head loss through the pool system, reduction of pump power consumption and the longevity of the heater by automatically taking the heater mostly out of the flow loop when not in use."

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com

-There are no downsides to adding a check or by pass valve other than cost and labor?

It adds to the complexity of your system and diagnosing heater problems. It becomes another point of failure and restriction in your plumbing flow.

 

[generessler]

I never tell a person not to buy insurance if it makes them comfortable but your rationale is on shaky ground:

• We see the OP has an IntelliChlor cell and the largest IC60 cell generates 2lb/day of chlorine, not 4
• Even if we stipulate that when you turn off the pump there can be a 9 ppm slug of chlorinated water in the 6 inch cell that cell is more than 5X its length away from the heater. And the pipe is going to full with water on both side of the cell. So that small slug of 9 ppm water will get diluted by water on both side of the cell before any of it gets into the heater.
• The FC levels you are worried about getting into the heater are less than SLAM FC levels. If your rationale about "high" chlorine levels damaging a heater were valid then the SLAM process would be damaging heater, which it does not.

It is acid in trichlor tablets that are the problem and the acidic water it creates even when the pump is off.

If you want a CV for "insurance" and to not worry about your warranty claims then by all means put one in your pool. My experience with Pentair warranty claims, and I collected on one for a MasterTemp heat exchanger, is they never asked about that.

Fair enough. But 9ppm is in the whole pipe downstream of the SWG. The situation of concern is flow from that section of pipe backward toward the pump. Under what conditions can that occur? Anything that admits air in that downstream section of pipe creates a siphon so long as the pad is above water level. Say a slow leak in a valve or similar.

Anyway, the CV may well be overly cautious. As I said, cheap insurance. With it I'm sure. Without it I'll always wonder. A new heater is $3.5k. The CV is $50. Not a hard decision.

 

[1poolman1]

I’m a first time pool owner and just starting to grasp the big picture. I’ve everyone here to thank for that. Thank you so much!
Some of what I’m gathering from the responses are noted below and I welcome any feedback if my understanding is not correct.
-Concentrated chlorine just sitting in a heater is bad. Very bad.
-Not using a tab feeder will help but may not completely prevent this from happening.
-My SWG (Pentair IC20) could possibly be considered a “chlorinator” by Pentair and could possibly void my heater’s warranty if a check valve is not used.
-A SWG or a tab feeder if installed, must be installed downstream of the heater.
-Installing a check valve at the heater intake will prevent water/chlorine from siphoning into the heater.
-Adding an automatic by pass valve could be an option to increase longevity. The automatic bypass valve is known as an “IntelliValve” by Pentair.
-There are no downsides to adding a check or by pass valve other than cost and labor?

Do not ever trust that Pentair (formerly Rainbow) "positive seal non-corrosive check valve" to do anything other than fail. They are sealed and you can't see the damage until it is too late, but it always happens. I've cut out 20 or 30 of them over the years and the "juice" from a tab feeder will distort the seal and allow it to go places you don't want it to go. Tab feeders were designed for commercial properties where many times the pumps run 24/7 and any risk is minimized. Doesn't work that way on a residence. Seems a good idea, but it isn't.

 

[OWSwimmer]

Incorrect.

Your CYA level buffers the chlorine and keeps a very low level of active chlorine.

CYA - Further Reading

www.troublefreepool.com

CYA Chlorine Relationship - Further Reading

www.troublefreepool.com

Incorrect.

It is the acid in the tablets that cause the concern.



Yes. But we have had no firsthand reports of anyone among our 200,000+ members being denied a warranty claim for that reason.



Correct.



Incorrect.

The CV goes at the heater OUTLET.



The IntelliValve is just the actuator for the diverter valve used in the bypass.

The MasterTemp Connected Heaters support an automatic heater bypass using an IntelliVlave connected to the socket labelled BP_VLV on the PCBA in the heater. Pentair has the AUTOMATIC BY-PASS VALVE KIT (P/N 462048) FOR MASTERTEMP® AND MAX-E-THERM® POOL AND SPA HEATERS

Pentair says "in conjunction with a Pentair IntelliFlo VF pump the automatic by-pass valve functionality of the latest MasterTemp heater will improve the head loss through the pool system, reduction of pump power consumption and the longevity of the heater by automatically taking the heater mostly out of the flow loop when not in use."

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com

It adds to the complexity of your system and diagnosing heater problems. It becomes another point of failure and restriction in your plumbing flow.

Thanks for the input and references. Lots of great information to help me expand my new pool ownership knowledge base.