Mastertemp 400 heater corroded parts inside

[JoeyBagODonuts]

Our Mastertemp 400 heater was recently serviced. It was purchased about three years ago and put into service about 2.5 years ago, in Central TX. The bypass was broken, blocking water flow. The bypass, o rings, gasket and a new regulator were replaced. The tech noted that he saw corrosion on internal parts that "could be from salt water or alkalinity". See pic below. Our alkalinity is typically 125-150 and Ph runs high during summer so I add about a gallon of muriatic acid per week when it's hot. I also add stabilizer to keep CYA around 50 or higher. Should I be concerned about corrosion of parts? Is there a good way to avoid this?



Also, the SWCG is now warning about water flow when the heater is not running and water is going through the heater. When the heater is running, green light. If I route water away from the heater, directly to the SWCG, green light. I asked the tech about this, his first thought is a dirty filter. I clean the cartridge filters every spring. At typical, low pump, operation filter gauge shows 10psi. At high speed, which we don't really use, the filter gauge shows 30psi. I see water flow in the SWCG when the light is red, so apparently it's low pressure. Does this seem like a filter issue? I would expect red light all the time if so. Maybe not.

 

[mas985]

That looks more like scale than corrosion. Probably because of the high PH/TA.

Can knock a piece off and put it in acid to see if it foams?

What is the CSI?

As for the SWG flow, 30 PSI seems pretty high for a cartridge filter even with a heater. Has it always been that high? Perhaps the heater bypass is not working?

To exclude the filter, remove the cartridges and then check PSI again.

 

[JamesW]

The bypass was broken, blocking water flow.

Did they find the plunger?

 

[JamesW]

 

[JoeyBagODonuts]

mas985 was right, my issue was scale buildup which is also clogging up my SWCG. I used the long metal kabob stick to clear most of it. One piece that came out was about the size of a saltine cracker.

I dropped the blue/white scale buildup in MA and it dissolved quickly. Can/should I try to get MA to flow through my equipment?

I usually allow PH to go to 8 and then pour a gallon of MA in the pool. My TA is usually around 125-150. Recently PH was 8 and TA was 150. I added a gallon of MA and the next day MA was 7.2 and TA was 125. My initial thought was to add more MA, however other comments at TFP.com say don't fret about high TA and pay more attention to PH. Is the scale buildup likely due to PH, TA or both?

 

[mas985]

Do you have high CH/TA/PH fill water?

If so, you may want to invest in an acid dosing system. Our fill water is very high in all three so I have a constant rise in CH/TA/PH which needs to be kept in check with MA and the only way I found that keeps levels relatively stable is with a dosing system. Dosing once per week may result in large swings that you are seeing so daily dosing can help keep things more stable.

Also, the best way I have found to mitigate scale issues with plaster, tile lines, heaters and SWGs is to monitor CSI because CH/TA/PH ALL contribute to scaling and CSI captures it all in a single number. I "try" to keep mine between -0.6 to -0.3 and have been doing so for the last 18 years without any issues. Even at that low of a CSI, the SWG cell still seems to collect a little scale albeit not as much as higher CSI.

BTW, next time you might want to use a bamboo skewer instead of metal. The metal can scratch the SWG cell plates which can lead to premature failure.