We have a new in-ground pool with spa that has been in service for just over a year.  It is a salt-water (chlorine generator) system with a Jandy LT 400,000 btu heater and Jandy CL cartridge filter system (CL 580, I think).  After months of normal use, we're suddenly showing a high pressure indication only in spa mode (about 12 psi above the pool mode pressure).  We cleaned the filters to eliminate that as a causal factor, but the heater pressure switch inidicator remains illuminated on startup and the heater will not ignite.  The spa jets still function, however, so I don't believe we have a pump problem.  We have had some foul weather here in Austin that may have contributed to our problem.  I've checked for debris in the heater exhaust, but I'm thinking this may be a simple valve problem, with the differential pressures between the pool and spa.  Can anyone step me through a spa pressure troubleshooting process based on the info provided?  The LT heater user manual is fairly worthless.  Thanks.

Marcus Miller

Thank you for writing to me. I am really a heater guy and have not had that much experience with non heater problems. Having said that, one thing that I ran into while servicing heaters for 25 years was that when there were flow or pressure problems with no obvious causes. I would  then look very carefully at valves. I have seen them break internally and look like they were open but in reality they were closed and the only way to see that was to take them apart. Filters also can fail. Debris can also be a tricky problem. Sometimes the only way to clear some pipes of leaves etc is to reverse the water flow through them. That is a last resort thing as it is a real pain. Good luck.

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