another irrigation pump question


Thanks for the pointers on the last one. Much appreciated. I had no idea there were suction limits. I have not talked to the corp yet but I have heard via others that they do issue permits for personal irrigation usage. And from the response to my last post I'm thinking the only practical solution for me is a shallow well jet pump. The pump can remain on my property and I can easily supply electrical power. Running power to the lake is out of the question because o fthe flood issues. The corp is very restrictive about that. I just have to run water lines down to the jet foot in the lake. That's the part I'm investigating now.
I'd like something cheap and easily taken up or moved if needed. I see that normally some pretty large pipe is used for a home jet pump. And it's not cheap. But I also only need to accomplish 30 psi at about 2 gpm. I'm wondering if I can get away with 1 inch poly for the main pipe and 1/2 inch poly for the jet supply? Any thoughts? Again the lake is about 250' away with a 25 to 30' rise to the house. Thanks to all :-)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Andy comments: I live on a lake which allows residents to use lake water for irrigation purposes. A permit costing $100 is required, and if any electrical service is taken onto the lake easement, it must also have a permit and be inspeccted. For that reason, I located the pump above the lake easement, which is about half way to the house and ran electric out to the pump...... Typcally, my pump is about 5 feet above the lake level and five feet below the house level. I use 1 inch PVC pipe as both input and output, and a foot valve at the lake end of the input pipe. The pump is from Harbor Freight and costs around $33, and will pump about 5 gallons a minute. www.harborfreight.com
This works well for me. I just use water for the garden an for the lawn and have laid out my irrigation so that the pump capacity will supply one zone at a time, rather than the whole shebang at once. Perhaps this idea will help you...
Andy in Eureka, Texas
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Thanks. That's along the lines of what I'd like to do. My issue is that our lake, Kerr, is a flood control lake. Any electrical must be on poles 20' above normal pool. Way too costly for my project. My house is about 25' to 30' above normal pool. Because of the electrical restrictions I need to locate the pump at my house and draw the water up the whole distance. I think that means I need to go a little more $ on the pump. But I've seen a number of 1/2hp ones in the $100 to $150 range. My only other cost is the water line so I'm trying to limit that too. I'm trying to run a drip system that has about 100 1gph drippers per segment so I don't need much.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I've talked to some of the neighbors who believe it is allowed. I still need to call over there and ask what the deal is. Some things you have to get a permit for and some things they just "approve" in writing. And some things you can just do. I'm hoping it's one of the later since they often come up with fees for the permits. Most of what you find online discusses large scale usage. A foot acre is a bunch of water. The corp is not very web present. I'm not planning on buying materials until I find out the rules. But that may prove painful since it's a bureaucracy. I'm trying to figure out if there is an economical solution to the engineering before I tackle the permission side. If there's not a moderately priced solution then I'll avoid that pain.
I've seen numerous sources for 1/2hp jet pumps in the $100 to $150 range. Amazon, ebay, etc. I expect they are somewhat cheaply made at that price but I'm thinking I'll be running it for a hour or so every couple days so cheap may be acceptable. I can accomidate a low flow rate since this is drip. The jet foot seems to be $30 to $50. The last piece of the puzzle is pipe. It's a long way. I'm guestimating 250 feet or so just based on looking at it and comparing it to a football field. Obviously I'll have to measure before I buy pipe if this turns out to be practical. Irrigation poly pipe seems to be the cheapest for long lengths. It is good up to 60psi which I think is ok for my application. But 1" seems to be the biggest size commonly found.
I've got no experience in the well or water pumping business so I came here to get some thoughts on my plan.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
jamesgangnc wrote:

My guess is that you'd need at least 3/4". In reality, you need to check with the manufacturer of the pump you select. They should be able to relate distance, rise, etc. to the need for different size pipes at particular pressure and gpm output.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Thanks, that's helpful. I can still use poly 3/4. I have not been able to find poly larger than 1". The poly is pretty cheap but most other options are not.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
jamesgangnc wrote:

Poly larger than 1" is certainly available, but maybe not at the Home Depot type of places. Not that you should need it for your low volume use.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I'd get a Convertible pump with a Shallow Well Ejector And try it with one pipe first 25' to 30' rise should work is it 25'-30' over a 250' area try it before the two pipe If not can you can still use the same pump I'm doing 150' with a 10'-15' rise and can do 3 sprinklers full on Did my neighbors when their sprinkler pump quit with no rise seemed the same as a 10'-15' rise over a 100' since its not straight up most pumps will do 25' Are you close to sea level I've done both Pump at lake and at house both have their problems I'm doing at lake with 1" poly for intake 20" from water edge and a 1" garden hose 100' to the tees for the regular garden hose intake of pump is 1-1/4 output is 1" just used a reducer to 1" poly fitting The larger pipe your talking about is the well casing not need here You are going to need a lake screen the one I got goes right on the check valve Then something to hold it down but off the bottom The pessure switch is right on the pump but with 3 sprinklers on runs full time with drip I think you'll need a pressure tank or will have Short cycling Also a Pressure relief valve would be a good idea if its going to run with you not right there I also ran a 1" Galvanized Pipe straight up from the pump about 3' with 2 faucets and a cap on top to prime also a garden hose holder u bolted to it The pump is bolted to a large board was going to stake to the ground but not needed stable enough with the board and a cement block sitting on the board even when pulling the hose The 1" poly pipe out front seems to hold it in place
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Are you sure of the 2 gpm rate? Seems a bit low to me but if all you need is 2 gpm then you could use 3/4" for the main pipe and 1/2 inch for the jet supply. Smaller pipe is easier to prime so don't over-size it. Get a good foot valve to make priming as easy as possible and hopefully one priming will last a long time. Priming and keeping prime is the main disadvantage of long pipe runs from the source.
For your 2 gpm you need a pump that will supply 2 gpm at 102 feet of head - 3 ft friction losses, 69 ft for the 30 psi pressure and 30 ft for the static lift. The equation for horsepower is hp = (gpm x head in feet)/ (3960 x efficiency) where efficiency for these pumps can be as low as 60% (0.60). That is only 0.09 hp for your 2 gpm need. You can use the smallest pump you can find that will make 102 ft of head at 2 gpm and that may be hard to find as small pumps usually don't make that much head.
I did the calculation for 5 gpm and get 22 feet of friction loss in a 3/4 inch pipe. That means a hp of (5gpm x 121 ft)/(3960 x 0.6) = 0.255 hp. So a 1/4 hp pump would supply a lot more than you need and that size is easy to find but again the head rating is important.
There is no problem with an over-size pump, in this case. The pump only draws as much power as it needs for the amount of water being pumped so even a 1/2 hp pump wouldn't waste much electricity. Running a pump lower than it's best range makes it operate in a less efficient range but that might be 50% instead of 60%. It wouldn't harm the pump physically because 2 gpm is enough to lube and cool. So, if you can only find the pressure requirement in a 1/2 hp pump and the price is right that is OK. Check the shut-off head (head at zero flow) to make sure that your pipe can handle that pressure. In the 1/2 hp range there are many pumps that make a lot of pressure so be careful of that.
Also, use a pressure tank and probably a 30/50 switch - starts pump when pressure falls below 30 psi and stops pump when pressure reaches 50 psi. You divide psi by 0.433 to get feet of head. The pump's shut-off head must be higher than the higher number of the switch or it won't make enough pressure to cause the switch to turn off. These switches are usually adjustable with a screwdriver so you can likely get a setting that will work with your pump - just turn all the taps off so flow is zero and if pump turns off at 50 psi, great. If it keeps running adjust the shut-off screw until pump stops and then turn screw a bit more.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Thankls everyone for all the info. It is a great help. Reno, you think a tank is really needed? I was originally thinking I'd just couple the output to the drip system and let the automatic controller turn the pump on when it opens a valve. I have seen some combo tank/ pumps that were not unreasonable but still a good deal more than just a pump. I realize I would need to group enough drippers so I was able to run a good deal of water through them.
I'm leaning towards the two pipe solution because we have had the lake drop during severe droughts. My suction requirement could go up another 8 to 10 feet if that happens. And that would be a period when I needed the system the most to irrigate.
I'm going to call the corp today and see what the deal is. Sounds like the engineering is not a show stopper.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

If you can make the pipe system leakproof and keep it that way for years then a tank is not strictly necesary. Small leakage only does harm when the pump is not supposed to be running. The leak lets pressures drop which starts the pump but since the major water use is closed the pressure immediately rises and stops the pump. It can cycle every minute or worse. More than 6 to 8 cycles per hour kills pumps. You could try going without a tank and monitor the pump for cycling when it is supposed to be off. If it cycles, find and fix the leak or if that proves difficult install a tank. Or skip the automatic controller and manually operate the pump valve.
Your tank may need to be 20 gallons or more in size, for the 2 gpm flow rate. Too small a tank will also cause cycling. Tank size must be matched to pump capacity, pump performance characteristics and system flow rate. If you don't know how to do this then you may be better off without a tank at all than to have a small tank causing the short cycling that you are trying to avoid. You can minimize cycling by using as large a spread as possible for the control switch. Switches come in settings of 30/50 or 40/60, etc which describe the start and stop pressures in psi. These numbers are designed for potable water applications where the pressure in a house system should not get too low or too high. These switches are usually adjustable so you could set it to something like 15/70. Many factors can influence these settings. If you are pumping uphill then the lower (start) pressure must be higher than the elevation difference converted to psi plus a bit. The higher (stop) pressure must be lower than the pump shut-off head or the pump will never reach this value and thus never shut off.
If your lake level drops significantly then that can affect the pump performance considerably. Since your 2 gpm load is much less than the likely pump selection there should be little impact. If the pump capacity is close to the applied load then you could have problems. Pump selection should be made by computing a system head curve and plotting this on the manufacturer's pump performance curve graph. Where these curves cross is where the pump will run - when some one says a pump makes 5 gpm at 120 feet head it means the curves cross at this point. Less flow will have more pressure and vice-versa. Some pumps have a steep performance curve which means that a large change in pressure has a small effect on flow. Some pumps have a flat curve which means that a small change in pressure will have a large effect on flow. Your case has large changes in lake level and these levels are included in the total pressure that a pump can make - if the lift increases then the pressure head is reduced. So a steep curve would be best as it would tolerate changes in lake level better. You would lose pressure at the drip line so get a pump for the worst case of lowest lake level. Add the lift, the losses and the required pressure at the drip line to get head at the needed flow.
The tank prevents frequent cycling of the pump. Cycling kills pumps for two reasons - 1) pumps draw about twice the amps for starting as they do while just running. This large draw heats up the motor windings which cool down while running. If the motor starts too often, more than about 6 or 8 times an hour, then the heat builds up and kills the motor. 2) The motor starter uses points just like in the old car distributors. The points carry a lot more amps than in cars which were high voltage but low amps. The high amp tends to wear out the points more quickly so it is best to minimize the number of starts. If you are lucky, frequent cycling will just trip the high temp protection for the pump motor - cheap motors might not have this. So you can monitor cycling rates by frequency of motor re-sets or wear rate of the points. A good system never needs new points and maybe a motor re-set once a year or two. Generally the pump and motor wear out before they give these problems.
The two pipe solution is definitely required for high lift cases such as yours. Suction lift is the same concept as a person sucking a drink up a straw. It is not the negative pressure sucking that moves fluid up the straw; it is atmospheric pressure pushing. Atmospheric pressure is 14.7 ps which computes to 33 feet of head. So if a pump could create perfect suctiion then the absolute maximum lift would be 33 feet vertical. Pumps are imperfect so their max lift is in the range of 28 feet for great pumps to about 20 feet for many pumps. Lift can be as low as 5 feet for some types of pumps such as trash pumps which have large clearances inside the casings to allow for large objects to pass through the pump. A cheap irrigation pump should be in the range of 18 to 22 feet. This will decrease with time because internal clearances will increase as the pump wears.
Say the pump can do 20 feet of lift. From this you must subtract hydraulic losses such as; friction loss, entrance loss, foot valve loss, and possibly other losses. Thus the 20 feet potential leaves only about 15 feet for actual vertical lifting. So if your case calls for more than about 15 feet of lift you must use either the two pipe system, move the pump lower and closer to the water source or use a submersible pump. I have had a lot of problems with pumps losing prime or being difficult to prime so I favour submersibles or locations where the pump suction lines can be as short as possible. As you describe the situation a two pipe system is the logical choice.
Another issue - you wish to pump for a drip system. Drips are sensitive to clogging by algae, dirt, etc. If your source is clean water then at a minimum you must use a good fine screen. Screens can plug and the way to minimize screen clogging is to use a large screen so flow velocity through the screen openings is lower. A large screen takes longer to clog so mainenance has a better chance to keep up. I often put a second, very large screen around an intake that is either disposable or at least easier to clean without pulling the intake. Locate the intake so screen condition is easy to see and easy to clean. If you have fine dirt or algae issues then you may need a filter in your system. The filter must be large enough and located downstream of the pump. The pump must be sized for the extra pressure loss of the filter. I like sand filters with backwash valves for some applications. Filter losses can be anything but 5 to 10 psi can be a good guess. Undersized filters can lose 20 psi or more. Put a pressure guage on both sides of the filter and backwash when it reaches the filter manufacturer's recomendation. Severe algae conditions would preclude a drip irrigation option as the frequent filter cleaning would be too much to keep up with. No filter and algae in the water would result in a plugged drip system that would essentially destroy it. Note that algae growth is worse for dry hot weather, just when irrigation need is highest.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Thanks again!
You might have missed, in my no tank scenario I would turn the pump on with the irrigation controls. So the pump would not run except when I actually needed water. Most irrigation controls have a pump lead that can be used to fire a 24v contactor.
I had not considered the filter issues. The lake water is very clean but obviously not perfect. I have the irrigation on a well now and simply use a small sand trap before the valves. So what I save on a tank might end up getting spent on a filter.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I did miss that. In this case a tank is not needed. Sometimes you can get a combination of start and stop pressures that cause a pump to start and stop repeatedly that is not the sort of thing a tank is intended to solve. This happens when the pump can hit the stop pressure while running. Either the pump makes too much pressure or the flow being drawn is too low for that pump. This may happen to you because you have a low flow low horsepower situation which may lead to an over-sized pump.
Easy solution would be to just throttle it down a bit. So make sure there is a valve in place downstream of the pump and preferably near the pump that you can turn down until it behaves. A globe valve will hold a setting better and be less likely to get 're-adjusted' by someone else. Ball valves are OK but need a wire or something to prevent them vibrating to a different setting. Hang a note on it stating it is a throttling valve and not to be adjusted by others.
If you are just running at 2 gpm you could try a simple screen filter like the one frim the site below;
http://www.sprinklersupplies4less.com/100250-complete-unit-mesh - polyester-p-22530.html
This is the 1 inch size 250 mesh screen. I have either this unit or something very similar on my geothermal open loop system, except in 1 1/2 inch size with 100 mesh and my filter box says BII on it. Looks the same as the photo.
The 250 mesh is recommended for drip irrigation. Cost is shown at $70 and replacement filters cost $36. These are tough units with clear cases so you can see if there is sand in the bottom that can be cleared by opening the valve for a second. You can also see if the filter is dirty. I have been cleaning mine every 3 months or so for 4 years and am still on the same filter. Use plumbers grease on the o-rings and threads everytime you re-assemble the unit and it should last a long time. Grease is essential or high forces are needed to remove the case to clean the filter and I am sure those forces will reduce the life of the unit. Sure reduced the life of my wrists before I twigged to the grease. Plumbers grease is best as some other greases will deteriorate plastics or rubbers. It can take a bit of force to turn the case into the body of the filter so make sure the body and it's pipes are securely anchored and can tolerate heavy twisting motions.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Thanks. I actually already have a 1 inch one of those because the well supply has some sand. Not sure if it's 250 mesh or not though. I was just stopping the sand. I'm guessing it will clog up faster with lake water.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.