Advice requested on replacement pool/spa heater


New member
Dec 12, 2021
Pool type: in-ground with integrated spa ~15K gallons

Pool heating: enersolar rooftop heating

Hi, I recently acquired a property that has an old raypak 185C/335C natural gas direct ignition heater manufactured around 1991. It looks like it has not been in used in a long time. When I open up the panel to inspect, the burner tray and pilot assembly has some serious corrosion on it. The unit does not operate and only a constant ticking is heard when turned on. Based on my guess, it is probably not worth it to repair it.

The 333K BTU pool heater was sized to heat both the pool and the spa, but later solar heating was installed to heat the pool. My question is what should the replacement heater be if I want to mainly heat the spa? I assume I wouldn't need 333K BTU, but at the same time, I don't want to downsize too much in case I feel that solar heating is not enough and want to slightly boost the pool temp with a gas heater. The idea is to use the spa all year round and the pool from late spring to early fall. The pool and spa both use the same pump and filter. Any advice gladly appreciated; thanks in advance!


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In The Industry
Jul 14, 2014
First, that heater is well beyond end of life. Even if it could fire, the corroded cabinet makes it a danger. A recommendation is, if you do purchase a RayPak (my heater of choice for 30 years), place it on 4 bricks to raise it off the pad a bit. I do so with every installation. I always thought they were too close to the pad (even the new ones) and the rust you see at the bottom of your cabinet is why. Debris will collect under the cabinet and they rust from the outside. Being a bit higher allows for cleaning underneath.
Usually the gas line that was installed for a 333 will be sufficient for a 400. Even if you only have 1" pipe (not likely) you can be 20 feet away from the meter with natural gas and 55 with propane according to RayPak's chart.
My recommendation has always been to get the largest heater you can use. What you are buying is speed of heating. A 400 will heat faster than a 333 as it supplies 1/3 more heat at any time. The difference in price is not that great when compared to the convenience.
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