Replace outdoor faucet with ball valve for max. flow?

Jamie Hall

A pump such as the booster @hot_rod suggests (there are other makes) will give you more pressure. What it will not give you is greater flow beyond whatever flow drops the pressure at your house inlet below about 0 psi gauge.

Assuming -- and it may be a bit of a stretch -- that your system static pressure in the street really is 50 psi, which is quite within standard and quite reasonable, and that your house lateral is also reasonable (even half inch will only lose about 0.2 psi per foot of pipe at 5 gpm) you should have ample pressure at the house (20 psi) to run any normal home sprinkler. Big agricultural sprinklers are a different matter -- a typical single head unit might run around 30 gpm at 20 psi inlet pressure, and covers half an acre.

Sprinklers are rarely, if ever, designed to require more than 20 psi for full operation -- and indeed, most of the consumer grade units have pressure reducing valves built into them to make sure that that is maintained. So additional pressure at the faucet or hose isn't going to help you much.

Now however if you want to run more sprinklers at once, you may indeed run into inadequate flow from the street (to go back to that head loss, 150 feet of half inch lateral will drop to 20 psi at the house).

At the risk of going one more time around the barn, the only way you can solve that problem is to store the water you need on site -- see my comment about a tank -- and have a pump to get it to your sprinkler array (such as @hot_rod 's suggestion).

hot_rod

The answer to your very first post, all things being equal is a YES.


When you start adding numbers to the problem the answer becomes a bit more math intensive. ie the time required to water 8,000 square feet with X amount of water in X amount of time. It too is a solvable problem.

As Sheryl once sung, "it's not about having what you want, but wanting what you got"

It's up to you if the juice is worth the squeeze.

sunlight33

Here's one sprinkler that provides more output than the average household ones:
https://www.bigsprinkler.com/catalog/lawn-garden/heavy-duty-sled-base-sprinklers/rotor-sprinkler-5-lb-weighted-sled-base
It can do 1.5 to 8 GPM at 45psi depending on the nozzle size.
Their largest sprinkler that can run off a standard faucet and 3/4'' hose does up to 25 GPM but that's way over what my supply can provide.

Jamie Hall

Yep. Bigger ones are certainly available. The real trick is to match the coverage area with the water delivery so that the water you are applying doesn't run off or even actually saturate the ground. This doesn't seem to be a problem in urban areas -- I've seen some pretty amazing young floods while driving around suburbia -- but for those who actually have to pay to pump the water (never mind those in areas where water is limited), a lot of attention is paid to matching the coverage, delivery rate, and timing relative to the weather, the soils and crop conditions.

In areas where water is really limited, it is truly amazing how little water one needs for things like crops in rows (vegetables, tomatoes, that kind of thing) or even trees (think almonds, oranges, lemons...) if one does it right. One doesn't sprinkle, of course -- that is reserved for things like wheat or hay (or nowadays, with the demand for biodiesel, soybeans!). One uses drip irrigation or microemitters. Corn does well with drip irrigation, though it's a nuisance when cultivating... One does not water lawns! There are places in the southwest where water is actually more valuable than oil.

sunlight33

Love the conversation in this thread.
I have another thing want clarification, my Watts PRV has fall-off pressure of 7 psi at 6 GPM, does this mean water loses 7 psi simply from flowing through the PRV? If so I can redo my piping to have the pipe going to outdoor faucet bypasses the PRV, is my thinking right?

Jamie Hall

sunlight33 said:

Love the conversation in this thread.
I have another thing want clarification, my Watts PRV has fall-off pressure of 7 psi at 6 GPM, does this mean water loses 7 psi simply from flowing through the PRV? If so I can redo my piping to have the pipe going to outdoor faucet bypasses the PRV, is my thinking right?

yes...

hot_rod

I thought you were at the top of a hill and did not need or have a PRV?
Check the pressure before the PRV, that is where sprinkler connection could be made. If it is under 80 psi you could connect hose bibs and sprinkler before the PRV. Any and every "device" you flow through adds some pressure drop, pipe included.

sunlight33

I do have a PRV, it was there when I bought my house. Now fall-off pressure shouldn't affect static pressure right? It could still be at 50 psi but as soon as water starts flowing it will drop by that much plus pipe. 

Also does fall-off pressure reduce flow rate? Fixtures inside the house could benefit if I change to a PRV with a lower fall-off.

hot_rod

here is a graph of several 3/4 PRV tested in our lab this week, for fall off pressure. No surprise Caleffi is the top performer In many cases a size smaller Caleffi PRV will outperform a larger sized competitor.

As flow increases pressure drops off, so as @Jamie Hall mentioned you need to look at the sprinkler head spec and match that to what you have available, if you want to work this exercise backwards.

Smart engineers size control valves, of any sort, with tables like this. Different opinions out there on what is an acceptable fall off for a building.

Personally I would take the PRV out of the equation, then you just need to look at piping and fitting losses.

Jamie Hall

sunlight33 said:

I do have a PRV, it was there when I bought my house. Now fall-off pressure shouldn't affect static pressure right? It could still be at 50 psi but as soon as water starts flowing it will drop by that much plus pipe. 

Also does fall-off pressure reduce flow rate? Fixtures inside the house could benefit if I change to a PRV with a lower fall-off.

Flow rate will be determined by the resistance to flow of the entire system. For the moment, ignore the losses in the water company piping. So -- you have your house lateral. You have a water meter. You have assorted miscellaneous fittings. You have a bunch of valves. You have more piping. You have a faucet or hose bibb. If you are thinking about the sprinkler, you have hose. You have the sprinkler.

Now. The rate of flow out of fixture X -- sprinkler, kitchen sink, whatever -- will be simply the flow rate at which the friction losses in all that stuff exactly equals the gauge pressure at the entrance to the house. No more, no less.

So yes, in a way, reducing the head loss through the PRV may result in an increase in flow through the system, out of whatever faucet or what have you is open. Will it for sure? That depends a lot on the ;fixture in question. Many newer fixtures have built in flow restrictors now, and have for a decade or two (shower heads, for instance). Those will see little or no change. For most fixtures almost all the head loss is in the fixture valves themselves -- those will see little change. And so on.

At this point I have to admit that I'm not quite sure what your objective in this exercise is. Perhaps we need to revisit the objective here?

sunlight33

Thanks for the explanation. All in all, my objective was to identity where pressure drops occur in my plumbing system and try to get as much pressure/flow as possible for both outside sprinkler and inside fixtures without spending a lot of money (like adding a booster pump). Right now when one flushes a toilet and turns on a faucet at the same time, the flow out of the faucet is slightly reduced, but if a second faucet is turned on too the flow would be reduced significantly. I want to see how this can be improved by re-piping the system.

hot_rod

Drop off pressure that you experience could be caused by an obstruction in your lateral like. Corrosion, a kink, a partially closed valve, under sized meter yoke, etc.
Is there a backflow device on the mainline somewhere? Sometimes the water provider adds one to a meter to comply with State or Federal funding requirements. A BFD would also add pressure drop.

So at the end of the day, you can flow test, or if you can measure all the components you can calculate what to expect at the end of your line. Flow testing give you an exact answer. Calculating would not take into account an unseen restriction.

If you need or want more, you need to change something as suggested in the above posts. Increasing openings will increase delivery, is that enough? Only you can answer that question.

sunlight33

No backflow preventer, it's a very simple system. Water main pipe (3/4'') coming in, PRV, then meter. I am going to put the PRV after the meter so I can add a tee in between the two to bypass the PRV for sprinkler.

Jamie Hall

sunlight33 said:

Thanks for the explanation. All in all, my objective was to identity where pressure drops occur in my plumbing system and try to get as much pressure/flow as possible for both outside sprinkler and inside fixtures without spending a lot of money (like adding a booster pump). Right now when one flushes a toilet and turns on a faucet at the same time, the flow out of the faucet is slightly reduced, but if a second faucet is turned on too the flow would be reduced significantly. I want to see how this can be improved by re-piping the system.

Well, as I mentioned, the pressure drop is a combination of the flow and the frictional resistance. There isn't much you can do about either the lateral from the main or the meter. They are there courtesy of your water company (though likely on your dime!). So you are, really, looking for places in your home where you can reduce your frictional resistance.

The first thing to look for -- besides the PRV (which, by the way, you may need -- most plumbing fixtures, while they won't usually actually break at more than 60 pis or so, aren't really happy with it) or a backflow preventer -- which your water company may require and which, if they do require it, must stay between the water meter and any other plumbing -- including your new hookup for your sprinkler -- is globe valves. Many older plumbing jobs used globe valves to shut off parts of the system for maintenance (nowadays we use ball valves). Globe valves, even fully open, have quite a bit of head loss. So you will want to replace all of those. Second is to check the size of your supply piping and its routing. Again, it is quite common to pipe single bathrooms with half inch copper supply lines (sometimes two bathrooms). You may find that in older jobs more of the piping is half inch. This I would point out, is perfectly within code requirements. It does, however, have more friction loss with flow than three quarter. Further, check the routing -- each elbow adds loss. So you may want to modify the routing to minimize elbows and Ts, and you may want to replace some or all of your half inch supply lines with three quarter inch. In some cases, if the interaction between say two bathrooms or a bath and a kitchen is objectionable, you may want to run separate three quarter inch lines for each point of use group from a common manifold near the PRV (for the cold) or the water heater (for the hot).

You will never be able to completely eliminate the interaction between fixtures -- if only because some of it will be, as I noted, in the lateral, the meter, the backflow preventer (if there) and the PRV.

Frankly, I personally would regard my suggestions above as overkill. However, tastes and perceptions differ, and you may be much more sensitive to variations from interactions than I am.

sunlight33

My water supply comes from a water tower (200k gal) nearby, the elevation difference results in 50 psi to my house, do you think I need a PRV as a safety measure?

Jamie Hall

No. 50 psi is the normal water pressure in domestic water systems in the United States and Canada.

To account for elevation differences, some water supplies run up to 80 psi, but try not to go over that, but even that is fine for any properly plumbed system.

It is worth noting, however, that some plumbing fixtures manufactured for and sold to EU or British standards may expect and be designed for much lower pressures -- typically 15 to 20 psi -- and now with the internet it may be possible to purchase these in North America. Just as with European electrical appliances, designed for 50 hz 240 volt power, using them in North American plumbing can have lamentable results. Buyer Beware!

sunlight33

Have a question on cross threading. I accidentally cross threaded the first two turns of the Big Blue filter housing inlet (plastic FPT) with a brass fitting, so I retracted it and threaded it the correct way, the male fitting was in for 8 out of the total 9 turns (with the outermost first turn or two in bad shape), it's in there pretty snug. Do you think it will hold water without a leak? I used both tape and dope.

Edit: I replaced male fitting with union fitting, just in case.