shurflo question- no vac readings on a no flow day

[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.