Hi, I have been struggling to the past few weeks with intermittent problems of hot water dropout on a 4 month old Navien NPE240A2 system.
Setup:
NPE 240A2 installed on exterior of home. External recirculation activated with dedicated return line using built in pump.
3 showers:
#1 (Hans-grohe thermostatic, 1.9 GPM shower head) within 20 feet of heater.
#2 (California faucets, thermostatic, 2.5 GPM shower head) about 50 feet pipe length from heater.
#3 (primary master bath shower, Hans-Grohe pressure balanced, 2.5 GPM shower head) about 80 feet from heater.
Problem:
Everything seemed to be working fine for 4 months, with occasional slight temperature fluctuations in the #3 shower, but nothing that would affect usability. But then in the past two weeks we started to experience the water turning lukewarm in the middle of a shower. This would sometimes improve if you turn the water off and immediately turn it back on, sometimes it would not improve with this maneuver. I also noticed during this time that the water heater would show a flow of only 0.8 GPM when shower #3 was on, even when the temperature was set to maximum. The flow from shower #2 was 1.6 GPM, slightly better, but still not near 2.5 GPM capacity of shower head in that bathroom. The flow from shower #1 was 1.0 GPM rather than the max of the head of 1.9.
I Called the plumbing company who installed the heater and they came out and did some tests. They checked my water inlet filter and said it was quite dirty which was likely due to the recent addition of bathroom #1 and new pipes being placed in that part of the house. They also ran some tests on my shower and said my cartridge in shower #3, the master bath, was somewhat faulty and should be replaced. Initially for about 24 hours it seemed that the problem was fixed by cleaning the filter alone, but then it started to recur, so I changed the cartridge with a brand new one. This did not fix the problem. So I called the plumber back. This time they got on the phone with Navien support. The first step they had us do was check the water pressure to the house. It was 40 PSI. They said that was very low and likely the root of all the problems I have been experiencing. They were not willing to run additional tests until I rectified this issue. This didn't really make sense because the heater worked just fine for 4 months. I called the city, and a very funny coincidence, the water main down the street from me happened to have a break that same morning we were troubleshooting. After it was fixed, I checked the pressure again, and it was up to 43 PSI. I spoke to the city and they said according to their survey book, my street has pressures ranging from 45-50 PSI at the hydrants, so the 43 PSI is not that far off. After the pressure was increased to 43 PSI, I checked the showers again and the flow seemed a bit better! I was getting 1.3 GPM from shower #3 instead of the prior 0.8. 2.2 from shower #2 instead of prior 1.6, and 1.3 from shower #1 instead of 1.0. Indeed shower #3 was now useable. It remained usable for 2 or 3 days, then again started to get lukewarm in the middle of the shower and indeed, the flow as down to 0.8 GPM again.
But the problem was intermittent. If you turn the shower off then turn it back on right away, it is hot again. I ran some more tests myself. I turned shower number #3 on max heat and the heater displayed 1.3 GPM, I kept the shower on, then I ran another faucet in the house, the total went up to 2.2 GPM, then after turning off the faucet, it went down to 0.8 GPM and would not come back up to 1.3 again. I turned the faucet on again and off again and this time the shower stayed at 1.3.
So in summary, I am getting lower than expected flow to all my showers, with the worst being the one furthest away from the heater, and the amount of flow to the furthest shower varies unpredictably between 0.8 GPM and 1.3 GPM. When it drops to 0.8 GPM the shower feels lukewarm. At 1.3 it is useable.
Questions:
1) Could this all be my lower than average water pressure of 43 PSI to the house? This might explain the greater reduction in flow to the furthest shower, but how does it explain the intermittent fluctuation in flow. Also, I assume the pressure to my house was no different when the system was installed 4 months ago and I didn't notice this problem.
2) Are pressure balanced shower cartridges more sensitive to lower hot water pressure than thermostatic ones? This could explain why shower #3 is worse than the others.
3) Could this be due to the Navien flow sensor? The plumber and Navien support said this was unlikely, because there is no error code and the heater is being triggered to run just fine. To me, a malfunctioning flow sensor would seem like a good explanation, but I'm not a plumber.
4) Is the recirculation line supposed to feel cold when the hot water is currently running through a fixture? When you feel the return line out by the water heater as it exits the house, it is quite cold and you can feel cold water flowing through it as the heater is running delivering hot water to the house.
From my online reading, I thought this could mean the check valve was malfunctioning, but the plumber said the check valve was not the problem because the output from the heater remained at 120 degrees the whole time.
Here is a video of the fluctuation in flow I am describing:
https://youtu.be/x4ARWRt-ucU
Any help would be greatly appreciated as my plumber seems stumped.
Setup:
NPE 240A2 installed on exterior of home. External recirculation activated with dedicated return line using built in pump.
3 showers:
#1 (Hans-grohe thermostatic, 1.9 GPM shower head) within 20 feet of heater.
#2 (California faucets, thermostatic, 2.5 GPM shower head) about 50 feet pipe length from heater.
#3 (primary master bath shower, Hans-Grohe pressure balanced, 2.5 GPM shower head) about 80 feet from heater.
Problem:
Everything seemed to be working fine for 4 months, with occasional slight temperature fluctuations in the #3 shower, but nothing that would affect usability. But then in the past two weeks we started to experience the water turning lukewarm in the middle of a shower. This would sometimes improve if you turn the water off and immediately turn it back on, sometimes it would not improve with this maneuver. I also noticed during this time that the water heater would show a flow of only 0.8 GPM when shower #3 was on, even when the temperature was set to maximum. The flow from shower #2 was 1.6 GPM, slightly better, but still not near 2.5 GPM capacity of shower head in that bathroom. The flow from shower #1 was 1.0 GPM rather than the max of the head of 1.9.
I Called the plumbing company who installed the heater and they came out and did some tests. They checked my water inlet filter and said it was quite dirty which was likely due to the recent addition of bathroom #1 and new pipes being placed in that part of the house. They also ran some tests on my shower and said my cartridge in shower #3, the master bath, was somewhat faulty and should be replaced. Initially for about 24 hours it seemed that the problem was fixed by cleaning the filter alone, but then it started to recur, so I changed the cartridge with a brand new one. This did not fix the problem. So I called the plumber back. This time they got on the phone with Navien support. The first step they had us do was check the water pressure to the house. It was 40 PSI. They said that was very low and likely the root of all the problems I have been experiencing. They were not willing to run additional tests until I rectified this issue. This didn't really make sense because the heater worked just fine for 4 months. I called the city, and a very funny coincidence, the water main down the street from me happened to have a break that same morning we were troubleshooting. After it was fixed, I checked the pressure again, and it was up to 43 PSI. I spoke to the city and they said according to their survey book, my street has pressures ranging from 45-50 PSI at the hydrants, so the 43 PSI is not that far off. After the pressure was increased to 43 PSI, I checked the showers again and the flow seemed a bit better! I was getting 1.3 GPM from shower #3 instead of the prior 0.8. 2.2 from shower #2 instead of prior 1.6, and 1.3 from shower #1 instead of 1.0. Indeed shower #3 was now useable. It remained usable for 2 or 3 days, then again started to get lukewarm in the middle of the shower and indeed, the flow as down to 0.8 GPM again.
But the problem was intermittent. If you turn the shower off then turn it back on right away, it is hot again. I ran some more tests myself. I turned shower number #3 on max heat and the heater displayed 1.3 GPM, I kept the shower on, then I ran another faucet in the house, the total went up to 2.2 GPM, then after turning off the faucet, it went down to 0.8 GPM and would not come back up to 1.3 again. I turned the faucet on again and off again and this time the shower stayed at 1.3.
So in summary, I am getting lower than expected flow to all my showers, with the worst being the one furthest away from the heater, and the amount of flow to the furthest shower varies unpredictably between 0.8 GPM and 1.3 GPM. When it drops to 0.8 GPM the shower feels lukewarm. At 1.3 it is useable.
Questions:
1) Could this all be my lower than average water pressure of 43 PSI to the house? This might explain the greater reduction in flow to the furthest shower, but how does it explain the intermittent fluctuation in flow. Also, I assume the pressure to my house was no different when the system was installed 4 months ago and I didn't notice this problem.
2) Are pressure balanced shower cartridges more sensitive to lower hot water pressure than thermostatic ones? This could explain why shower #3 is worse than the others.
3) Could this be due to the Navien flow sensor? The plumber and Navien support said this was unlikely, because there is no error code and the heater is being triggered to run just fine. To me, a malfunctioning flow sensor would seem like a good explanation, but I'm not a plumber.
4) Is the recirculation line supposed to feel cold when the hot water is currently running through a fixture? When you feel the return line out by the water heater as it exits the house, it is quite cold and you can feel cold water flowing through it as the heater is running delivering hot water to the house.
From my online reading, I thought this could mean the check valve was malfunctioning, but the plumber said the check valve was not the problem because the output from the heater remained at 120 degrees the whole time.
Here is a video of the fluctuation in flow I am describing:
https://youtu.be/x4ARWRt-ucU
Any help would be greatly appreciated as my plumber seems stumped.
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