Can a “silent” check valve fail and become not silent?
December 22, 2018 7:36 PM Subscribe
Has my “silent” check valve on my sump pump failed?
We have a sump pump in the basement. For many years it made a big “thump” sound when it finished ejecting water - I assume this was a check valve closing with force. About a year ago we had the pump replaced and the plumber also installed a “silent” check valve. The thump was greatly reduced. In the past few weeks, though, the thump is back as loud as ever. Looking on the web, it looks pretty easy to replace a check valve. Before I do that - does it make any sense to think that a valve installed within the past year is the culprit? Can a silent check valve become un-silent? I figure if it’s anything more complicated I will need the plumber.
We have a sump pump in the basement. For many years it made a big “thump” sound when it finished ejecting water - I assume this was a check valve closing with force. About a year ago we had the pump replaced and the plumber also installed a “silent” check valve. The thump was greatly reduced. In the past few weeks, though, the thump is back as loud as ever. Looking on the web, it looks pretty easy to replace a check valve. Before I do that - does it make any sense to think that a valve installed within the past year is the culprit? Can a silent check valve become un-silent? I figure if it’s anything more complicated I will need the plumber.
If the thump didn't entirely disappear when you had the "silent" check valve put in, the thump was not caused by the check valve itself.
Try this: get down into your sump, and disconnect the sump from the check valve, and the check valve from the piping. The water downstream of the sump should empty out. Then connect everything back up exactly the way you found it, and see if the thump is softer.
The reason why the thump was greatly reduced after the installation of a new check valve might have something to do with the filled/not-filled condition of the pipes immediately following installation of the new check valve.
If there is a high place and a feature that behaves as a trap in your outflow piping, some air will be retained in that high place, which could greatly reduce the thump in the downstream pipes. Over time, that air dissolves in the passing water, and disappears. With the loss of the easy compressibility of that retained air, the thump gets louder.
IMPORTANT NOTES:
DO NOT perform speculative plumbing over the holidays.
PROPERLY anticipate the amount of water that could flow into the sump after you disconnect the check valve, and plan accordingly (measure the feet of pipe above the sump pump, compute the volume of that pipe and assume that it is full of water, and compute how far it will rise in the sump if that water flowed back into the sump). You might have to set up another pump to empty the sump in order to work on it.
NOTE that disturbing any plumbing might mean that you have to replace something, perhaps a coupling if you can't get the fasteners apart, etc. Choose a time when you can do without what you are working on for a day or two (not in a torrential rainstorm, perhaps). Start your plumbing work very early in the day, when you will be able to obtain spare parts; or better yet, anticipate any parts you might need, buy them, perform the operation, and then return what you didn't use.
JUST DON'T perform speculative plumbing over the holidays.
posted by the Real Dan at 11:12 AM on December 23, 2018 [2 favorites]
Try this: get down into your sump, and disconnect the sump from the check valve, and the check valve from the piping. The water downstream of the sump should empty out. Then connect everything back up exactly the way you found it, and see if the thump is softer.
The reason why the thump was greatly reduced after the installation of a new check valve might have something to do with the filled/not-filled condition of the pipes immediately following installation of the new check valve.
If there is a high place and a feature that behaves as a trap in your outflow piping, some air will be retained in that high place, which could greatly reduce the thump in the downstream pipes. Over time, that air dissolves in the passing water, and disappears. With the loss of the easy compressibility of that retained air, the thump gets louder.
IMPORTANT NOTES:
DO NOT perform speculative plumbing over the holidays.
PROPERLY anticipate the amount of water that could flow into the sump after you disconnect the check valve, and plan accordingly (measure the feet of pipe above the sump pump, compute the volume of that pipe and assume that it is full of water, and compute how far it will rise in the sump if that water flowed back into the sump). You might have to set up another pump to empty the sump in order to work on it.
NOTE that disturbing any plumbing might mean that you have to replace something, perhaps a coupling if you can't get the fasteners apart, etc. Choose a time when you can do without what you are working on for a day or two (not in a torrential rainstorm, perhaps). Start your plumbing work very early in the day, when you will be able to obtain spare parts; or better yet, anticipate any parts you might need, buy them, perform the operation, and then return what you didn't use.
JUST DON'T perform speculative plumbing over the holidays.
posted by the Real Dan at 11:12 AM on December 23, 2018 [2 favorites]
The thunk is actually water hammer. The reason you had it previously is that the check valve closed only when the water column reversed flow, and was then quickly stopped by the valve which closed due to flow reversal. A silent check has a spring in it, it will close before the water column has time to reverse flow, this reducing the pressure wave (water hammer, the thunk). I’m guessing that over time the spring has failed in your silent check valve, and it’s now working as a standard check, closing only when the flow has reversed. Replacing the valve is trivial in principal, but can easily go pear shaped if the connections to the pipe are corroded or damaged, poor access etc etc.
posted by defcom1 at 8:47 PM on December 23, 2018
posted by defcom1 at 8:47 PM on December 23, 2018
This thread is closed to new comments.
Good luck!
posted by cooker girl at 7:50 PM on December 22, 2018