Help with water hammer

[JonLondon]

Before we has a small irrigation sprinkler installed at our home a couple of weeks ago, the only time I could hear any water hammer was if I opened an upper-floor faucet full force and slammed it shut - I would hear one thump that lasted a second in the bathroom itself.

Then we had an in-ground sprinkler installed, and now, if I flush a toilet at night (in a different bathroom off our bedroom), then run a faucet briefly, there is sometimes (but not always) a loud, groaning sound that lasts for about 10 seconds and comes from farther away. Also, two toilets that previously were running fine are now running long after they are flushed.

Our house is on city water with a psi about 78 at the street and a bit lower in the house. The water enters the house through a metre in the basement. The water runs up from the metre to near the basement ceiling and turns 90 degrees to run below the ceiling, all in 3/4" copper pipes. When the plumber attached the sprinkler to the water supply, he made a t-connection a few inches from the initial 90-turn, connecting the T to 1" plex which then runs almost straight 30 feet to an exterior wall, so the plex line is perpendicular but in the same plane as the main line. Outside the exterior wall the pipe runs up to a backflow preventer, then down beneath grade to a master valve.

I have not heard problems when the sprinklers are running but believe the problems are related to the sprinkler installation since they only appeared after the installation.

What might be wrong? How do I diagnose the problem? How can it be fixed?

Thanks for all and any suggestions.

Jon

 

[dextrous]

Check the pipes have enough clips to hold them in place. Or try turning the main supply tap down a bit.

 

[JonLondon]

Check the pipes have enough clips to hold them in place. Or try turning the main supply tap down a bit.

Thanks for the suggestions. The only new pipes are plex (plastic) and they seem quite well secured. Nothing else on the system has been changed. Since the pipes weren't making noise before the irrigation, it seems to me the irrigation line has created new/different pressures and I rather fix that problem than chasing after the symptoms.

 

[dextrous]

Insufficient pipe supports and variation of flow rate though the main tap are potential causes, not symptoms of water hammer.

 

[JonLondon]

Insufficient pipe supports and variation of flow rate though the main tap are potential causes, not symptoms of water hammer.

Since the new Pex pipe is well-supported, that would leave a variation in the flow rate. Since this only appeared after the irrigation was installed, how might that have changed the flow rates given the setup I described?

Thanks again for your help.

 

[dextrous]

Could be a simple as when he turned the supply tap back on after doing his work, it's open to a different position to before. Sounds daft, but has been known. Would also explain the longer fill times for your toilet cisterns.

 

[JonLondon]

Could be a simple as when he turned the supply tap back on after doing his work, it's open to a different position to before. Sounds daft, but has been known. Would also explain the longer fill times for your toilet cisterns.

The sound from the toilets I assumed (maybe wrongly) was of water running because it was now leaking from the cistern to the bowl of the toilets, and that leaking was the result of the same pressure issue that brought on the sounds in the pipes. What do you thinK?

 

[dextrous]

Unless you have completely different WC systems over there, the time taken for a flush to complete will remain constant regardless of how quickly the cistern fills. Once a cistern has refilled, a valve will turn the supply into it off, regardless of any fluctuations in pressure.

If the cisterns are leaking into the toilet pans now then this would mean that the valves would never turn off, and water hammer would not be able to take place. If this has happened subsequent to his work, then apart from coincidence I cannot explain it.

So, if it is taking longer for the cisterns to refill, it indicates that the flow rate is different to what it was before. And it is this difference that is causing the water hammer in the pipework. So,, as said previously, adjusting the main tap (stopcock) from the rising mains supply may resolve the problem.

 

[JonLondon]

Unless you have completely different WC systems over there, the time taken for a flush to complete will remain constant regardless of how quickly the cistern fills. Once a cistern has refilled, a valve will turn the supply into it off, regardless of any fluctuations in pressure.

If the cisterns are leaking into the toilet pans now then this would mean that the valves would never turn off, and water hammer would not be able to take place. If this has happened subsequent to his work, then apart from coincidence I cannot explain it.

So, if it is taking longer for the cisterns to refill, it indicates that the flow rate is different to what it was before. And it is this difference that is causing the water hammer in the pipework. So,, as said previously, adjusting the main tap (stopcock) from the rising mains supply may resolve the problem.

I'll try the adjustment. Thanks for the suggestion.

 

[JonLondon]

I checked the main tap and it was fully open so I don't think that's the problem.

A couple of updates:

I checked the following:

(1) No clamps have been removed from the piping in the basement.
(2) The sound is more like a steady groan that lasts five to ten seconds rather than a percussive hammer sound and seems to come from the basement.
(3) The last time I heard the sound -- this morning when an upstairs toilet and sink were used for the first time since last night -- the sound started while the sink water was still running.

When I add those observations together, I wonder if it's the case that water pressure along the long Pex line to the sprinkler is greater than water pressure through the copper tubing that is used elsewhere in the basement. The Pex line is 1-inch; the copper is 3/4". Is it possible that when water is drawn from the house, water in the Pex line is running backwards to the T-connection to the main copper line and causing it to vibrate?

The walls of the Pex line is thicker than copper, so the interior dimension isn't 1/4" bigger, but it may be somewhat bigger. If that is the problem, how might it be fixed?