shurflo question- no vac readings on a no flow day

[Earthman]

Hi all- Little foggy and need a reminder.....got a shurflo pump and am not getting any vac readings at the manifold. Everything is tight, etc. Does it need sap to get any reading at vac gauge?

Thanks,
Mike

[BSD]

Hi all- Little foggy and need a reminder.....got a shurflo pump and am not getting any vac readings at the manifold. Everything is tight, etc. Does it need sap to get any reading at vac gauge?

Thanks,
Mikeyes. the diaphragm isn't powerful enough to suck all the air out of the tubing without sap to prime it.

[Earthman]

Great, thanks for your response. Really appreciated.
Mike

[maple flats]

That's the reason many who use a diaphragm pump design it with a small recirculating line. Then when the flow is slight, the recirculation line keeps the diaphragm wet so it makes better vacuum. That line can be a 3/16 or 5/16 line from the storage tank and it can have a needle valve to slow the recirculation, it takes very little to make the pump work far better.

[Biz]

I usually see 10" of vacuum on my units under no-flow conditions on 3/16" lines, 200 to 600 ft long. If you have longer runs or using larger tubing it can take a while to build up vacuum, but you should see some vacuum even dry with no flow. To prove this, take the pump with inlet or strainer disconnected, power it up and hold your hand over the end - you will feel a good vacuum. Not 30" but probably 10". If you don't see good vacuum, perhaps the pump diaphragm is damaged.

A recirculation helps as Dave says but you must restrict it or it won't work well - 5/16 recirc line is way too big for this size pump unless you add a needle valve or ball valve cracked open slightly. Even 3/16 is too big unless restricted. It doesn't need much liquid to boost vacuum, and too much will cause a drop in vacuum on your sap line.

Dave

[Haynes Forest Products]

These style pumps are liquid pumps and not air pumps. Yes self priming pumps will generate SOME vacuum. The higher vacuum comes when it sucks the liquid from the line creating a higher vacuum. Plus liquid creates a better seal so you will get higher vacuum with liquid present.
Now if you have a glycerin filled valve that was manufactured anywhere else other than your back yard you need to BURP it. You need to take a small instrument and lift the little black rubber fill port on the housing. Now don't go popping it out spilling the liquid all over yourself just open it until it equalizes. I have had my gauge jump 4 points.

[Mark B]

While we are talking about a recirculation line to keep a wet diaphragm, do I have to run that recirculation line back from my tank, or can I plumb it from the outgoing line on the pump back to one of my incoming lines?

[Haynes Forest Products]

Air and liquids take a path of least resistance. If you have a recirculation line you will lower your vacuum at the main line. Now the reason Surflow pumps are so desirable is they can run all day long dry without damage. I would think the only reason to run liquid on a contious basis is because the pump is warn or defective. To me it makes no sense to run a recirc line to try and improve a pump with low sucking ability by lowering the vacuum/suction with a recirc line. To me its like driving as fast as you can to the gas station before you run out of gas.

[RileySugarbush]

Haynes: The recirc helps keep the vacuum level up on these little pumps. I believe it works by helping seal the check valves, and filling the volume of the pump so the diaphragm is pulling on incompressible sap instead of air.

On a day with low flow, there is not enough sap coming down the lines to keep the pump wet and the vac level drops so it takes longer to get the sap flowing out of the trees. The vacuum level is not there. Once things start running you can close it down.

I agree in makes no since to recirculate when the trees are running well since there is plenty running through the pump already, but on those marginal days you can really see the difference when you crack open a needle valve on the recirculation line. It is important to have a restriction ( the needle valve) so the recirculation flow doesn't overload the pump. I put a vacuum gage at the pump so you can dial in the best position for that valve.

[BAP]

Air and liquids take a path of least resistance. If you have a recirculation line you will lower your vacuum at the main line. Now the reason Surflow pumps are so desirable is they can run all day long dry without damage. I would think the only reason to run liquid on a contious basis is because the pump is warn or defective. To me it makes no sense to run a recirc line to try and improve a pump with low sucking ability by lowering the vacuum/suction with a recirc line. To me its like driving as fast as you can to the gas station before you run out of gas.
Shurflo pumps and other diaphragm style pumps will pull higher vacuum if they have liquid constantly running through them. They can run dry, but move liquid better than just plain air. That is why, keeping them wet makes them work better. The re-circulation line does that. The best way to hook up the line is to put it in the tank with a needle valve in the line to fine tune the amount being pulled out of the tank. You only want just enough to keep the pump constantly pumping liquid. I have the Shurflo 4008, and without the re circulation line I was running 10-15" of vacuum. With the line, I pull 20-24" of vacuum on 100 taps. It has nothing to do with the pump being worn or not.

[Haynes Forest Products]

I stand Corrected because not one post mentioned shutting down the flow after higher vacuum levels were achieved.

[Haynes Forest Products]

Now that brings up another dilemma. If you have an over sized pump for the capabilities of the tubing system you are building in the NOT ENOUGH LIQUID to run the system and you will always have cavitation lowering your vacuum levels...................Right??

[RileySugarbush]

Not really the case

A diaphragm pump will have an optimum flow rate for generating vacuum, where the fresh sap flow rate is far below the full open flow rating of the pump. Open flow rate is 3 or 3.5 gpm on a shurflo, or 180 gallons per hour. Nobody is going to have that many taps on a little pump like that, so we will always be operating well below the open flow rate. I haven't done detailed tests, but I have about 50 taps on my shurflo, and on a great run I suppose it might flow 100 gallons over a 10 hour period, or less than 0.2 gpm. Thats plenty of flow for keeping the diaphragm wet and working well. You can see that a little recirculation throttled in could maybe double or triple that flow through the pump and still be well below the open flow rating. So even if you leave the recirculating line open on good days, it still works ok, and is there to fill in if the trees slow down.

There will always be some bubbles in the lines, always some air going through the pump, but the recirculation line keeps something in the pump when things slow down.

[Mark B]

No offense, but my original question is still unanswered. Can I just tap the out going line on the pump side or should I run a line back from my collection tank. I really can't see any difference.

[RileySugarbush]

No offense, but my original question is still unanswered. Can I just tap the out going line on the pump side or should I run a line back from my collection tank. I really can't see any difference.
Got distracted I guess!

I have multiple suction lines and drop one into the tank for recirculating, with a needle valve to limit flow. If you pull off your outlet line you risk not having a steady Source in low flow situations, which is when you want to assure a wet pump.

[awpoolco]

which shurflo? I am using a NorthStar NSQ Series 12V On-Demand Diaphragm Pump - 3 GPM @ 60 PSI. It works well but I only achieve 12" on 100 taps even with a recirculating line. Brand new diaphragms, same as last season. Are the shurflo pumps that much better?

[McKenney Maples]

I use a 4008, 12V 55psi and 3.0 GPM I can pull 18-20" H2O. After I've walked the lines a few times and have everything "leak free".

[awpoolco]

Do you think there is that much difference between the two pumps

[awpoolco]

So BAP says he gets 20-24" on 100 taps. really? Cause I want some of that.

[awpoolco]

Well I guess the only way to really know is to buy the shurflo 4008, so done!! It will be here Wed. I will keep you posted. I did note some differences, at least in the written description. Shurflo does not say "ON Demand" but there is a "check valve" listed on the shurflo. Who knows if the other has same characteristics. Priming distance is less

[KReinisch]

I have a 4008 running 22" on 225 taps. I have the re-circulation line but I have only had to use it to prime the pump and then once it starts sucking sap, it takes off.

[Biz]

I have two 4008 pumps, one on a line of 22 taps and one on a line of about 40 taps. I don't use recirculation on either one, and am seeing 20-25" at the pump inlet with sap flowing. I believe recirc only helps get the flow started.

awpoolco: sounds like you may have a leak if you are only getting 12". I see 10-12" with zero flow. If lines look tight check fittings around the pump. If there is a leak you it is very difficult to find under vacuum, better found with pressure. What you can do is block the outlet of the pump using a pcv coupler and plug, or use an adaptor to a piece of tubing folded over on itself and taped off. Then remove sap line, make up an adaptor to an air fitting, pressurize to 25psi, and spray water or use a wet rag, or even just drip water or sap around all fittings. If there is a leak you will know it, it will bubble. If the unit is in the woods, you might be able to make up a tire fitting and use a tire pump. Stainless fittings are the worst, needs plumbers goop to seal properly.
Good luck!

Dave

[McKenney Maples]

Yeah I agree the re-circulation line really just helps to keep the vacuum up when sap flow is low or just starting up. I just checked my pump today and I'm pulling 20-22"....can't complain.

[awpoolco]

Well I guess the only way to really know is to buy the shurflo 4008, so done!! It will be here Wed. I will keep you posted. I did note some differences, at least in the written description. Shurflo does not say "ON Demand" but there is a "check valve" listed on the shurflo. Who knows if the other has same characteristics. Priming distance is less

[awpoolco]

All advice taken, Thank you. I do have a leak and I am still trying to find it. Isolation and air pressure with a tire pump. More to come...

[n8hutch]

You could have a leak at a tap or a hollow tree/rotten tree, those are hard to find, also I found with my guzzler pump that if you keep the outlet side of the pump a few inches higher than the inlet you can gain an inch or two more vac because they pump doesn't get any air in its pumping stroke if that makes sense, learned that one by accident.

[KReinisch]

I found a leak in a hollow tree. It was killing me and I found it by accident. Make sure you look hard.

[Stiets]

Great tips and tricks for vacuums pumps systems, thank you guys. I am about to hook up my first vacuum pump this weekend. I plan on having a recirculation line but don't have a needle valve yet.

What are you guys using for a needle valve that works with 3/16"? Can you post a pic or link?

In the meantime I was going to try to clamp the tubing to try restrict it.

[awpoolco]

Did you know that the shurflo pump has a check valve in it? The Northstar pump I have been using does not and I think that is the reason for my low vacuum. new pump here today and we will know for sure.

[awpoolco]

Thanks everyone. I ditched my pump and switched to shurflo 4008 and I have more sap and vacuum than I ever thought I would. Marginal day and I held 18" on 225 taps, 4 runs one with 47, one with 75, on with 53 and the last with 50 taps. Next year I will set up a real mainline and limit my lateral taps. This fully automated collection is awesome.

[Dale Sparrow]

which shurflo? I am using a NorthStar NSQ Series 12V On-Demand Diaphragm Pump - 3 GPM @ 60 PSI. It works well but I only achieve 12" on 100 taps even with a recirculating line. Brand new diaphragms, same as last season. Are the shurflo pumps that much better?
Yes, shurflo is that much better. The most I got from a northstar was 18", replaced it with a shurflo 4048 and started getting 24".

[Dale Sparrow]

I have a 4008 running 22" on 225 taps. I have the re-circulation line but I have only had to use it to prime the pump and then once it starts sucking sap, it takes off. What size mainline, how long?

[Dale Sparrow]

Just curious, what size mainline are you using and how long?