Salt water pool heater: does a salt pool need a special one?

A salt pool can run the same gas heater or heat pump as a chlorine pool. What decides how long it lasts is the chemistry table in its manual, and where the salt cell sits on the pad.

Pentair’s MasterTemp guide says the heater is designed for “chlorine, bromine or salt system swimming pools and spas” (MasterTemp manual, p. 3). Every other manual below handles salt the same way, with a salt figure in its water-chemistry table. So in these manuals, a salt water pool heater is an ordinary heater kept inside its limits. Below is what each current manual says, page by page.

Does a salt pool need a special heater?

It needs one whose salt limit sits above the level your cell runs at. Most heaters below clear that with room to spare.

Hayward’s AquaRite manual puts ideal salt at 2,700–3,400 ppm, with 3,200 ppm optimal (AquaRite manual, p. 4). Every stated maximum below is 4,500 ppm or more. Lochinvar is the one to read closely. Its EnergyRite table gives a recommended 3,000 ppm for residential pools, under AquaRite’s optimum. A caution then warns that salt above 5,000 ppm “can cause rapid corrosion to the heat exchanger” (EnergyRite manual, p. 35).

Salt limits, maker by maker

Each row comes from the maker’s own chemistry table, in the seven-brand order.

The Rheem, Raypak and Jandy figures are the “Other Pool and Spa Types” column. Fiberglass pools get their own column: pH 7.3–7.4, alkalinity 120–150 ppm, calcium 200–300 ppm (Raypak gas manual, p. 5). The same tables allow total dissolved solids up to 6,000 ppm in salt-chlorinated pools. Rheem’s manuals are Raypak documents; the gas manual carries Raypak’s Oxnard address (Rheem gas manual, p. 48), which is why those two rows match.

Pentair puts the stakes in a footnote. Missing a starred limit, salt included, “may result in premature failure of the heat exchanger and will void the heater warranty” (MasterTemp manual, p. 60).

What wears a heater in a salt pool

The manuals name three threats: salt over the limit, chlorine spikes from the cell, and pH out of range.

Salt first. Hayward’s table lists high salt as “corrosive to heat exchanger” (Universal H-Series manual, p. 27).

Chlorine is the quieter one. AquaRite is an “Electronic Chlorine Generator” whose cell is “plumbed in the return line” (AquaRite manual, cover and p. 12). Raypak warns that salt chlorinators “are usually more efficient in heated water, unless controlled, they can lead to excessive chlorine level which can damage your heater” (Raypak gas manual, p. 5). The same page caps free chlorine at 5 ppm. Pentair’s maximum is also 5.0 ppm (MasterTemp manual, p. 60).

Then pH. Pentair says low pH can cause “corrosion of copper tubes in the heater, which may cause leaks.” High pH raises “danger of scale formation” in the exchanger tubing (MasterTemp manual, p. 60). Jandy adds conditions. Above pH 7.8, with hardness and alkalinity not properly maintained, calcium can coat the copper tubes. Below 7.2, with alkalinity not properly maintained, acidic water can dissolve them (JXi manual, p. 42).

Two manuals boil the balance down to one number. Jandy’s JXi manual uses the Langelier Saturation Index: 0 is perfectly balanced, negative corrosive, positive scale-forming, ±0.3 ideal (JXi manual, p. 43). Hayward’s AquaRite manual calls water balanced at 0 ±0.2 (AquaRite manual, p. 3).

Every warranty quoted here leaves chemistry damage to the owner. “Heat exchanger damage resulting from chemical imbalance is not covered by the warranty,” says Pentair (MasterTemp manual, p. 59). Raypak: “Damage due to poor water chemistry is not a warrantable defect” (Raypak gas manual, p. 5). Lochinvar excludes lime scale from high hardness and alkalinity (EnergyRite manual, p. 3). Jandy’s maker excludes exchangers “damaged by corrosive water issues or from the build-up of calcium” (JXi manual, p. 43). Raypak’s warranty also names “electrolysis due to an improperly installed salt chlorine generator” (Raypak limited warranty, p. 2).

The salt cell goes after the heater

All seven brands’ manuals put the chlorinator downstream of the heater, and most want a check valve between the two.

The reason is back-siphoning, which Pentair says “is most likely to occur when the pump stops” (MasterTemp manual, p. 14). Here is how each manual words the rule:

• Pentair and Sta-Rite want the chlorinator downstream and lower than the heater outlet, with check valve P/N R172288 between them (MasterTemp, p. 59; Max-E-Therm, p. 54).
• Hayward wants the same: downstream, at a lower elevation, behind “a separate positive seal corrosion resistant check valve” (Universal H-Series manual, p. 18).
• Lochinvar says chlorinators “must feed downstream of the pool heater and have an anti-siphoning device” (EnergyRite manual, p. 35).
• Raypak prints it in the piping steps: “Salt generators and chemical feeders must be downstream of the pool heater” (Raypak gas manual, p. 20). Rheem’s gas manual says the same (p. 17).
• Jandy makes sanitizing equipment “the last piece of equipment in the pool circulation system,” with a chemically resistant check valve (JXi manual, p. 31).

The salt-cell side agrees. AquaRite’s preferred installation is “after (downstream) all the pool equipment (filter, heater, solar, etc.)” (AquaRite manual, p. 12).

When a cell wears out, we replace Hayward AquaRite cells and power units. We also work on Pentair IntelliChlor, Jandy AquaPure and Jandy TruClear (salt cells).

Cupro-nickel and titanium exchangers

Tougher water-side metals exist, but no maker drops its chemistry table for them.

Hayward makes cupro-nickel standard on all its gas heaters (Hayward cupro-nickel sell sheet). The Universal H-Series manual lists “Cupronickel water tubes standard” (p. 7), yet its warranty still excludes chemistry damage (p. 27). Lochinvar offers an optional cupro-nickel exchanger and a bronze header on EnergyRite (Lochinvar ERN402A product page). Raypak sells residential cupro-nickel versions of the 206A–406A, model numbers ending in -X (Raypak gas manual, p. 13, Table H). Its parts list says copper and cupro-nickel exchangers “are not interchangeable” (p. 46). Rheem’s gas manual lists cupro-nickel exchanger assemblies too (p. 43). On the Jandy JXi, the 260 and 400 models ending NN or PN carry a cupro-nickel exchanger (JXi manual, p. 51).

Two heat-pump manuals here name titanium. Hayward’s HeatPro manual says its “Titanium heat exchanger withstands the harshest water conditions” (HeatPro manual, p. 5). The same manual still sets 2,700–5,000 ppm salt (p. 25). Its municipal-water rule adds: “mineral water, seawater (PPM>5000), or other non-potable waters will invalidate the warranty” (p. 12). Raypak’s Crosswind lists “Titanium in PVC” (Crosswind manual, p. 21) and keeps the 4,500 ppm maximum (p. 6).

Because the metal is an option on some lines, read the full model number off the rating plate before ordering an exchanger.

Salt air is a separate problem

A beachside pad takes salt on the outside of the cabinet, which the manuals treat on its own. On a Brevard pad near the Atlantic, a salt pool sees salt twice: in the water and in the air.

Hayward tells oceanfront owners to keep the heater “out of direct spray of sand and salt.” Damage from sand or salt spray “is not covered by the warranty” (Universal H-Series manual, p. 11; HeatPro manual, p. 10). Pentair’s Max-E-Therm manual says to “avoid operation in persistent, extreme, moist or salty environments” (Max-E-Therm manual, p. 18). What a yearly tune-up looks at is on our maintenance page.

Replacing a heater on a salt pool

Before you sign a quote, get the full model number and find that model’s chemistry table. Compare your last salt reading with the table’s maximum, using the table above.

Next, look at where the salt cell sits. Every brand above puts it downstream of the heater, and most want a check valve between the two. Pentair, Sta-Rite and Hayward also want it lower than the heater outlet. If your pad has the cell ahead of the heater, or no valve, raise that before you sign.

Last, the exchanger metal. Cupro-nickel is standard on Hayward gas heaters and an option on some other lines, so confirm the model number matches the metal you are quoted. Raypak warns that copper and cupro-nickel heat exchangers “are not interchangeable” (Raypak gas manual, p. 46).

Sizing and choosing a heater live on our pool heater installation page.

Sources

• Pentair, MasterTemp Pool and Spa Heater Installation and User’s Guide, pp. 3, 14, 59, 60.
• Pentair, Sta-Rite Max-E-Therm Pool and Spa Installation and User’s Guide, pp. 18, 54, 55.
• Hayward, In-Ground Pool/Spa Gas Heaters Owner’s Manual, 51300004201 Rev E, pp. 7, 11, 18, 27.
• Hayward, Cupro Nickel sell sheet (LITCUPRO18).
• Hayward, HeatPro Heat Pump Installation and Operation Manual, 51300056501 Rev G, pp. 5, 10, 12, 25.
• Hayward, AquaRite Owner’s Manual, 092540 Rev G, pp. 3, 4, 12.
• Lochinvar, EnergyRite Installation & Operation Manual, Rev L, pp. 3, 35.
• Lochinvar, EnergyRite ERN402-A product page.
• Raypak, Gas-Fired Pool and Spa Heater, Models 206A–406A, P/N 241236 Rev. 50, pp. 5, 13, 20, 46.
• Raypak, Crosswind Inverter Heat Pump Installation and Operation Manual, P/N 241827 Rev. 06, pp. 6, 21.
• Raypak, Pool Heater Limited Warranty, P/N 100-10000378 Rev. 10, p. 2.
• Rheem, Gas-Fired Pool and Spa Heater, Low NOx 207A–407A, P/N 241793 Rev. 11, pp. 5, 17, 43, 48.
• Rheem, Heat Pump Pool & Spa Heater, Models 2450–8450, P/N 241909 Rev. 2, p. 6.
• Jandy, JXi Gas-Fired Pool and Spa Heater Installation and Operation Manual, pp. 31, 42, 43, 51.