When my well pump turns on, there is almost no sound from the water system pipes. If you're not paying attention you can't hear it. However when the pump stops, there is a very loud THUMP which can be heard from almost anywhere on the first floor of the house. There is no such thump when you turn on a faucet, shower, or even a fast-moving valve like on the dishwasher or washing machine. It only happens when the pump turns off. The previous homeowner had the well and pump installed in 2016 after having to give up his previous "gentleman's agreement" water supply from a neighboring property's well. So the well and pump are pretty fresh but the pressure tank has been in service a while. The previous owner mentioned the thumping sound when we bought the property 2 years ago, but I don't know if it was going on from Day 1 of the installation. I was new to well systems then and didn't know to ask further.
There are no surge arrestors or expansion tanks in the system. Only the pressure tank provides any buffer to pressure spikes.
Oddly, though, the local pressure gauge needle does NOT spike when the pump stops and I hear that thump. It stops cleanly upon pump shutdown. I have watched some YouTube vids of pressure gauge needle action on systems suffering from water hammer and my gauge doesn't act like that at all. Couldn't ask for a cleaner, more stable pressure response at shutdown.
Observations:
- Per what I see on the gauge during a cycle, the pressure switch is set for a on/off cycle of 43 psi to 67 psi. This is after a local well guy tweaked the switch trying to fix the problem. This switch was replaced 1 year ago after the original one's contacts got worn out after 13 years service.
- With the system depressurized and drained, the WellXTrol WX-202 pressure tank's air pressure is 38 psi. The tank has been in service 13 years but shows no apparent signs of failure/waterlogging. As best as I can recall, it takes over 1 minute upon pump start at 43 psi to reach 67 psi (may be longer, it's been a while) and once the pump stops at 67 psi, the system stays pressurized there with no bleed down. Tapping on the sides shows water where it should be and air where it should be. The tank seems OK.
- I went along the cold water lines in the crawlspace and added some pipe supports. However there is a vertical pipe run up to a 2nd floor bathroom where I can't access the lines and I think the pipe banging may be in there.
- The well pump has an internal check valve. Critically, I do not know if there are more check valves in the drop pipe. I don't think I see another check valve near the pressure tank & switch but I'll have to take another look.
- At the wellhead before the pipe goes underground to the house, there is a hose bib connection. I'd love to attach a pressure transducer there and get the pressure response on a graph on a computer, but I haven't found an affordable hardware option for that.
So is this really water hammer? Or just some poorly supported cold water lines? I have read that water hammer can happen so fast you never see it on a gauge, but could the needle really stay so stable at pump shutdown if there was hammer going on? Since there's no THUMP when the pump starts, that rules out a check valve failure, right?
Well system overview:
- 625' deep into bedrock
- pump set at 400'
- static water at 140'
- 30gpm yield (wow!)
- pump is 1.5hp Schaefer Series V 2-wire, 10gpm 230v, model 10SV15S4-2W230. Pump installed in 2016.
- 1" PVC drop pipe
- from the well head, it's about a 50' horizontal run to the pressure tank, with only a few tees & elbows
- duty cycle on the system is light since only 2 people live here
Thanks for reading, I'm curious what the old hands here think.
I'm also curious as to why such a powerful pump is set so deep on such a high capacity well, but that is a topic for another thread.
There are no surge arrestors or expansion tanks in the system. Only the pressure tank provides any buffer to pressure spikes.
Oddly, though, the local pressure gauge needle does NOT spike when the pump stops and I hear that thump. It stops cleanly upon pump shutdown. I have watched some YouTube vids of pressure gauge needle action on systems suffering from water hammer and my gauge doesn't act like that at all. Couldn't ask for a cleaner, more stable pressure response at shutdown.
Observations:
- Per what I see on the gauge during a cycle, the pressure switch is set for a on/off cycle of 43 psi to 67 psi. This is after a local well guy tweaked the switch trying to fix the problem. This switch was replaced 1 year ago after the original one's contacts got worn out after 13 years service.
- With the system depressurized and drained, the WellXTrol WX-202 pressure tank's air pressure is 38 psi. The tank has been in service 13 years but shows no apparent signs of failure/waterlogging. As best as I can recall, it takes over 1 minute upon pump start at 43 psi to reach 67 psi (may be longer, it's been a while) and once the pump stops at 67 psi, the system stays pressurized there with no bleed down. Tapping on the sides shows water where it should be and air where it should be. The tank seems OK.
- I went along the cold water lines in the crawlspace and added some pipe supports. However there is a vertical pipe run up to a 2nd floor bathroom where I can't access the lines and I think the pipe banging may be in there.
- The well pump has an internal check valve. Critically, I do not know if there are more check valves in the drop pipe. I don't think I see another check valve near the pressure tank & switch but I'll have to take another look.
- At the wellhead before the pipe goes underground to the house, there is a hose bib connection. I'd love to attach a pressure transducer there and get the pressure response on a graph on a computer, but I haven't found an affordable hardware option for that.
So is this really water hammer? Or just some poorly supported cold water lines? I have read that water hammer can happen so fast you never see it on a gauge, but could the needle really stay so stable at pump shutdown if there was hammer going on? Since there's no THUMP when the pump starts, that rules out a check valve failure, right?
Well system overview:
- 625' deep into bedrock
- pump set at 400'
- static water at 140'
- 30gpm yield (wow!)
- pump is 1.5hp Schaefer Series V 2-wire, 10gpm 230v, model 10SV15S4-2W230. Pump installed in 2016.
- 1" PVC drop pipe
- from the well head, it's about a 50' horizontal run to the pressure tank, with only a few tees & elbows
- duty cycle on the system is light since only 2 people live here
Thanks for reading, I'm curious what the old hands here think.
I'm also curious as to why such a powerful pump is set so deep on such a high capacity well, but that is a topic for another thread.