# Hose bib or bypass?



## davegravy (Jul 25, 2019)

I know the recommendation generally is to avoid using the hose bib for irrigation systems. I want to confirm, but I think in my case there's no benefit to bypassing the bib.

The line coming in from the city to the meter is 1/2", all the piping in my house is 1/2" CTS, including the pipe that goes to my hose bib. With the bucket test I measure ~5.3GPM at the bib which is close to the theoretical max safe flow for 1/2" (6GPM).

I suppose there may be some brief narrowing in the spigot itself which might be limiting flow a bit. Am I likely to see any benefit from running a dedicated line to my irrigation system without increasing my main supply from the city? Probably not, right?


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## hsvtoolfool (Jul 23, 2018)

davegravy said:


> Am I likely to see any benefit from running a dedicated line to my irrigation system...


Yes. The benefits include...



Better flow rates that may be significant. If your flow is marginal, then every little bit helps.



A separate pressure reducing valve can be installed for the irrigation system. 



Avoids water hammer damage to home plumbing.



Avoids "scrubbing" wear on home plumbing. Water is slightly abrasive and wears pinholes over time.


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## davegravy (Jul 25, 2019)

hsvtoolfool said:


> davegravy said:
> 
> 
> > Am I likely to see any benefit from running a dedicated line to my irrigation system...
> ...


My heads I think already regulate internally to 40PSI, would the benefit of the pressure reducing valve be to protect my tubing which is only rated to 100 psi?

My controller seems to have the ability to turn valves on slowly so there's no (audible) hammer.


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## hsvtoolfool (Jul 23, 2018)

davegravy said:


> ...would the benefit of the pressure reducing valve be to protect my tubing which is only rated to 100 psi?


The main benefit of teeing off before your house is to get the best possible flow. With a 1/2" mainline, it may be a serious challenge to design a safe, reliable irrigation system. The other main benefit is to avoid doubling or tripling the amount of water flowing through your plumbing. Water is an abrasive and erodes pipes.

As for pressure, every good plumber I've ever asked recommends about 60 PSI as a maximum safe pressure going into your house. Water hammer is unavoidable. Noise and vibration are just side effects. There's always a pressure wave in a closed system when the water flow is stopped. The spike can be minimized by keeping the baseline, static pressure below about 60 PSI.

With a 1/2" mainline, and assuming pressure is 60 PSI maximum going into your house, you may not have enough flow after the water navigates your home plumbing. You never stated your pressure at the hose bib, but I'm guessing it's pretty high if you're getting about 6 GPM from a 1/2" plumbing system.

My curb pressure is about 110 PSI so a PRV is essential. My PRV failed and I spent a weekend replacing it recently. Who knows how long I had 110 PSI running inside my home pipes? My pipes never made a sound! I only discovered the problem after I did a pressure and flow test from a hose bib. The 5 gallon bucket filled in less than 20 seconds! *I got a pressure spike around 150 PSI as I slowly turned off the hose bib by hand.* This is just scary for home plumbing. Sure my morning showers were invigorating, but my washing machine line could have burst at any time.

I run my home pressure at 60 PSI and limit my irrigation system to about 50 PSI. That way I have good strong showers in the morning and my irrigation system has minimal water hammer issues. I have a 1" mainline and 3/4" secondaries for maximum flow to each zone. Your pressure needs will be higher since you have a 1/2" mainline.



davegravy said:


> My controller seems to have the ability to turn valves on slowly so there's no (audible) hammer.


I don't think controllers turn off valves slowly. My understanding is that irrigation valves are engineered to close slowly to limit pressure spikes. It's a mechanical property of how the valves work. My Hunter ICV globe valves make a funny fluttering noise for several seconds as they close.


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## davegravy (Jul 25, 2019)

hsvtoolfool said:


> davegravy said:
> 
> 
> > ...would the benefit of the pressure reducing valve be to protect my tubing which is only rated to 100 psi?
> ...


My hose bib static pressure is 80PSI. When I run my oscillating sprinkler off it, pressure drops to about 30PSI.

I put an Orbit valve on my hose bib and wired it to a Z-wave power switch, to give me some remote control of the sprinkler. When I shut off the sprinkler through z-wave there's a loud "thud" (water hammer I assume) which can be heard through the house. I picked up an 4 zone wifi-based Orbit controller and hooked it up to the same valve in place of the Z-wave switch and the thud is completely gone, so there's *something* the controller is doing differently with how it's closing the valve. I assumed it's gradually turning off the valve, more similar to a human turning a ball valve which doesn't generate any audible hammer.

Sounds like I should assess how high the pressure spikes when closing valves as a basis for whether or not my system is at risk of causing damage - how high a spike is too high? Or you think I should just assume bypassing the bib is necessary, measurements be damned?


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## hsvtoolfool (Jul 23, 2018)

Interesting! I've never used Orbit valves, but they're all pretty simple gadgets. Maybe Orbit uses a different design that allows it to close instantly.

My best advice is to install a PRV and limit it to 60 PSI maximum to protect your house plumbing. Better safe than sorry.

Pressure spikes are roughly measures with a gauge that has a "max" needle. I don't now what a "safe" spike would be. Ideally, you want no pressure spike at all.

If it's feasible to install a "T" off your mainline, then I would do that. Especially with a 1/2" mainline. Every little flow restriction you can remove helps in your case. It would help tremendously to upgrade your mainline and / or meter to match the utility pipe size. I would hope they have at least a 3/4" pipe on the utility side of the meter.


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## davegravy (Jul 25, 2019)

hsvtoolfool said:


> Interesting! I've never used Orbit valves, but they're all pretty simple gadgets. Maybe Orbit uses a different design that allows it to close instantly.


They're just spring solenoids, soon as you stop supplying current to them the spring snaps the plunger back. In theory, if you stop current to them gradually instead of suddenly the plunger will move more gracefully. I imagine that's what the Orbit controller is doing, maybe with a capacitor or inductor. I'm more electrically inclined than mechanically if you couldn't already tell 



hsvtoolfool said:


> My best advice is to install a PRV and limit it to 60 PSI maximum to protect your house plumbing. Better safe than sorry.
> 
> Pressure spikes are roughly measures with a gauge that has a "max" needle. I don't now what a "safe" spike would be. Ideally, you want no pressure spike at all.
> 
> If it's feasible to install a "T" off your mainline, then I would do that. Especially with a 1/2" mainline. Every little flow restriction you can remove helps in your case. It would help tremendously to upgrade your mainline and / or meter to match the utility pipe size. I would hope they have at least a 3/4" pipe on the utility side of the meter.


The path from my mainline to my hose bib is pretty direct already... if I ran a new line I'd be pretty much following the exact same path... same number of elbows and same length of run. I could use a larger pipe, however.

Unfortunately the utility side is also 1/2". It's an old house and that was apparently the standard. I've been looking into cost to upgrade the utility side - seems like about $3k or so, but the bigger issue is I think the line comes in direct under some mature japanese maples that would be big $$ to deal with and that we would dearly miss if killed.

Thanks by the way for your insight.


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## hsvtoolfool (Jul 23, 2018)

Yeah, that sucks. A 1/2" supply will make it hard to run more than a few heads per zone. You can make it work, but you'll need to be careful will your maths and run more zones. If you don't care about increased wear on your home plumbing, you might try a "T" off the line just before the hose bib exits the house. I don't know what the flow loss will be through a hose bib, but bybassing any restictions can help marginal GPM work.

I hope this helps! Keep us posted on your progress.

This is off-topic but irrigation valves are pretty clever. A small solenoid isn't strong enough to open or close a spring that can seal against 100 PSI. The solenoid actually uses the water pressure itself to operate the diagpham. Irrigation valves won't open without water pressure.

When opening, the solenoid moves a tiny plunger and unblocks an orifice. This orifice bypasses the diaphram. Water slowly floods behind the diaphram until the pressure equalizes on both sides. The spring pressure can eventually open the diaphram fully. When closing, the solenoid closes the orifice and water pressure gradually drops behind the diaphram until the spring forces the diaphram closed.

It's very interesting that using a true irrigation controller had an effect on your valve operation. Perhaps true irrigation controllers reduce the DC voltage in stages so that the solenoid closes slowly which then slows the pressure drop behind the diaphram. Or maybe irrigation controllers "pulse" the solenoid open and closed a few times to slow the diagpham closing? Maybe there's a web article somewhere on why it's a bad idea to use a simple relay to operate irrigation valves. I'll email my Hunter contact and ask.


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## davegravy (Jul 25, 2019)

hsvtoolfool said:


> Yeah, that sucks. A 1/2" supply will make it hard to run more than a few heads per zone. You can make it work, but you'll need to be careful will your maths and run more zones. If you don't care about increased wear on your home plumbing, you might try a "T" off the line just before the hose bib exits the house. I don't know what the flow loss will be through a hose bib, but bybassing any restictions can help marginal GPM work.
> 
> I hope this helps! Keep us posted on your progress.
> 
> ...


I should also note that in a couple years we're planning a house reno which will gut the main floor and expand the foundation beyond where the hose bib is currently, as well as re-landscaping the yard. The POC location plus the position of all the heads will change, so I'm doing everything above ground, as a temporary setup just to reduce the amount of sprinkler jockeying I need to do. The hope is to bury everything and do a more professional install with the reno. Likely I'll spring for the utility upgrade and replace a bunch of old small piping with larger pex in the basement.

I've got minimal number of heads per zone in my plan, with no more than about 3.5GPM based on the manufacturer spec sheet. Need 4 zones to cover 2500sqft with this, which is painfully slow to get an inch down, but it's better than waking up at the crack of dawn to move sprinklers. I think that should be pretty safe on the piping in terms of flow?

I ordered parts online from a blog post for a DIY controller using relays and a microcontroller with wifi. Parts shipping got delayed so I borrowed the Orbit controller and now I'm thinking the DIY design may need some tweaking. I'll probably throw a scope on the Orbit terminals to see what's going on there once I'm back from my road trip. I'd be curious to know what Hunter has to say.


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## hsvtoolfool (Jul 23, 2018)

davegravy said:


> I've got minimal number of heads per zone in my plan, with no more than about 3.5GPM based on the manufacturer spec sheet.


Calculating the water velocity is easy once you know the GPM and your pipe size...

3.5 GPM with 1/2" pipe = 5.7 feet / second (danger Will Robinson!)

3.5 GPM with 3/4" pipe = 2.5 feet / second (okay!)

2.5 GPM with 1/2" pipe = 2.5 feet / second (okay)

You have a 1/2" mainline, and the max recommended water velocity for the mainline pipe is about 5 f/s. Since you can't replace it with a 1" or 3/4" pipe, I strongly recommend planning for about 2.5 GPM per zone maximum. You may end up with a lot of zones.

If you haven't read Mr Stryker's Irrigation Tutorials, then I also recommend that site. It's easy reading and will steer you right.


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