Hot water recirculation pump orientation

[Bannerman]

My suggestion was to use 1 expansion tank located on the irrigation supply line to provide double duty to cushion the water hammer issue as close as possible to the source of the water hammer, and also address the water heater expansion issue when a backflow device is eventually installed on the incoming line from the city supply. For the expansion issue, the location of the X-tank within the plumbing system is not important as long as there is no check-valve or other backflow prevention device or isolation valve located between the WH & X-tank.

As your home is not equipped with a booster pump to raise water pressure, there is no other reason the plumbing pressure is unusually high, even while water is flowing from a faucet. The source of the high pressure must be from the city, which appears to be an intermittent problem they may not be yet aware of.

 

[Bannerman]

If you wish to install your own pressure regulator where the city water enters your home, perhaps a watertight irrigation valve box would be a suitable enclosure, buried flush with your grass surface.
https://www.sprinklerwarehouse.com/products/lawn-irrigation/valve-boxes

If you install your own regulator, setting it to a high of 50-55 psi, should ensure your home plumbing will not be subjected to higher pressure regardless of the pressure arriving from the city.

 

[Sponsor]

 

[Niccolo]

Turns out there was some kind of utility issue and the neighborhood experienced super high pressures this morning. Several people reported burst pipes

 

[Jadnashua]

CPVC piping is less tolerant of excessive pressure. PEX will balloon some, but if it used plastic fittings, those might have a problem. To burst copper takes over 2000-psi, and if that happened, everyone would have had a really bad day! It could have killed someone. If a copper piping system burst, the joints weren't made well. Now, a compression fitting could blow off if it wasn't tightened properly, but have worked okay under normal pressures, but that isn't really a burst pipe.

A hammer arrester just before the control valves of your irrigation system should work if it is large enough. An expansion tank could function as one, but costs more, and you probably don't want that hanging around outside. Many of them (well, all that I've seen) are painted steel, and may not fare well outside for long term in the weather.

As long as you don't exceed the pressure range of the PRV you select, it should work.

 

[Niccolo]

Anyone have guidance on choosing a water hammer arrestor to have installed as close upstream of my two irrigation valves as possible (attaching photos)? Home Depot has only a few models in stock, most have to be ordered. Most are about $10, the most expensive around $35.

My thought is that a male threaded arrestor screwed into a female threaded PVC T-fitting would allow an arrestor to be easily swapped out if it were defective or after a few years if it needed replacement. But there are other ways to mate an arrestor with the pipes.

I'm not sure whether the size of the arrestor matters, but all things equal, I'm guessing somewhat larger is better than smaller. My steady state pressure is ~55 PSI but the water hammer shock is momentarily driving my cheap pressure gauge to between 120-200+ PSI, if accurate.

My impression is that the arrestor simply needs to be attached, the particular geometry isn't critical. Sort of like a sediment trap, is it beneficial for the water stream to change direction 90 degrees at the arrestor, so the shock wave can travel directly into the arrestor? I'm guessing since water is so incompressible, it doesn't matter, but maybe it does?

Anything else?

 

[wwhitney]

On the right side, you've got an extra pipe going into the ground: the rightmost with the valve is presumably the supply line, and one of the other two feeds those two irrigation valves. Do you know where the third one goes?

Cheers, Wayne

 

[Niccolo]

On the right side, you've got an extra pipe going into the ground: the rightmost with the valve is presumably the supply line, and one of the other two feeds those two irrigation valves. Do you know where the third one goes?

Cheers, Wayne

I think the answer is 1) supply 2) irrigation 3) pipe that runs around the house and serves a spigot on the other side of the house (and which could someday also serve irrigation on that side of the house).

The prior homeowners put in the PVC pipes that serve spigots on two sides of the house; I had a contractor put in the irrigation setup on one side of the house.

There are also two other outdoor spigots served by the house plumbing. Actually, it just occurred to me that if I install a water softener, which would make the water not good for irrigation, the irrigation system would still be running off unsoftened water and I could also do manual irrigation off that water, too, that's helpful. I suppose it's also possible the external spigots are all set up to not be served by softened water (the garage has an unused loop for attaching a water softener built in).

 

[Jadnashua]

Because the screw on fittings tend to be IPS, or tapered, driving the 'wedge' shaped end of the arrestor into a plastic female fitting over time can cause it to crack. Driving a PVC male into a metal female tends to work, though.

 

[Niccolo]

Because the screw on fittings tend to be IPS, or tapered, driving the 'wedge' shaped end of the arrestor into a plastic female fitting over time can cause it to crack. Driving a PVC male into a metal female tends to work, though.

Hmm, the irrigation pipes are PVC, I'm not sure how viable it would be to incorporate a metal segment for the purposes of having a metal place to attach a hammer arrestor. And I haven't seen any PVC threaded male hammer arrestors, either. The Home Depot website has dozens of hammer arrestors, and of course I could source one somewhere else, too.

 

[wwhitney]

PVC male adapter -- brass threaded coupling -- male threaded water hammer arrestor

Wayne

 

[Niccolo]

PVC male adapter -- brass threaded coupling -- male threaded water hammer arrestor

Wayne

So the brass threaded coupling would not be tapered but the water hammer arrestor would be?

 

[wwhitney]

You want the plastic to be the male side of the tapered, threaded connection, not the female side of the connection.

The female side of the connection is more stressed than the male side, because (a) a ring is stronger in compression than tension and (b) the compressive strength of a material is often a bit higher than tensile strength (seems to be true for PVC).

So since plastic is weaker than metal, you put the weaker material on the male side.

Cheers, Wayne

 

[Niccolo]

You want the plastic to be the male side of the tapered, threaded connection, not the female side of the connection.

The female side of the connection is more stressed than the male side, because (a) a ring is stronger in compression than tension and (b) compressive strength of a material is often a bit higher than tensile strength (seems to be true for PVC).

So since plastic is weaker than metal, you put the weaker material on the male side.

Cheers, Wayne

I just realized I misunderstood the original suggestion, I was picturing the brass coupling as male-female, not female-female. All clear.