Need help with vac issues on a Shurflo 4008.

I need some thoughts on the 4008.

Best vac I've seen is 14 inches. It settled back the other day and held at 10 to 11. Today I arrived nothing's running... it's holding it 5 to 6. I walked the lines looking for leaks and could find nothing. I have two separate runs with independent shut offs. I shut both down and then watch the vacuum on those lines to see if they held with everything shut down and they maintained the small amount of vacuum in them for 10 minutes without leaking off. So I'm thinking that there's nothing wrong with the lines.

However, I also deadheaded the pump with a vac gauge in place and watched the vacuum and the best it ever pulled was about 8 in.

With the inlet port blocked off and vacuum pulled, I shut the pump down and watched the gauges for 10 minutes and again they maintain that for 10 minutes and there was no loss.

I'm starting to wonder if maybe I have a bad diaphragm in the pump. Are there adjustments to the pump like an aqua tech? I know there are set screws on the front face but I believe they're adjusting the cycling nature of the pump.

Is this 4008 AC or DC? Do you run a recirc line from your tank to keep the diaphragm wet? I get usually 20" without any leaks. I did have one go bad/weak on me once. I have also pulled them apart to find a lot of gunk/debris in the diaphragm that was causing it not to seal up properly. Pretty easy to pull the head off to check.

If there is no sap flowing then your only going to get 6-7, how many taps do you have running to it. I have 175 and once the sap starts flowing I can get up to 25 inches. For me i can identify leaks by watching for excessive air in one of my 7 runs entering the manifold. Once I identify the run with a leak I walk and look for drastic changes in the speed of sap flow, normally found at a connector or sometimes a squirrel chew.


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Its a dc powered by a 12v dc led power box. 12v output was 12.5 volts on my meter. Yes I have a recirculation line in place.

I checked all my lines today and nothing was really moving. I do have a couple lines with sap in them but not moving quickly. Again I blocked off all lines one at a time and the vac guages show them holding vacuum. I also blocked off/ isolated the the pump, drew vacuum, and it maintained the vacuum it had pulled. The other day the sap ran and I saw 14 inches. Yesterday and the day before it ran again but only showed 10-11 inches. Yes today is/ was slow. I'm still thinking that I might have a bad diaphragm.

Also check that your manifold before the pump is tight, thread tape on all screw joints, ect. I had a leak at my shurflo manifold and it was an easy fix. But it sure sounds like a leak is somewhere.

Do you have a screen on the suction side? It could be a bad diaphragm or something in one of the check valves creating a bad seal.

All thread taped... Have the screen filter in line on the incoming line. When lines are shut down, the vac maintains. Gotta think its a diaphragm issue.

I have a spare pump so I can easily swap it out to keep the sap flowing, then repair the faulty one. Bothers me when a pump is down and I am not getting the production I should be... :) These pumps are pretty cheap.

Where this is my first year and I'm hobby I have not yet bought myself a backup pump but that's a great idea. The other issue I'm facing is that this is a brand new pump bought the end of December for the season and the third-party Amazon seller is refusing to work with me. The pump should be under warranty and should be replaceable if I can prove defect. The problem I am facing is proving defect to people who have never considered this use for one of these pumps. One of the technicians from the third party seller actually told me that this is not meant for sap that it's meant for water. I asked him via email if he realized that sap was essentially water.

I called Shurflo Pentair directly and talk to them but because it is so late in the day most of their technicians have gone home. The customer service lady was very nice and when I explained to her what I was using the pump for she thought it was a novel idea but wanted to refer to a technician to be diagnosed. She was amazed when I told her that she could go to maple trader and research the use of the Shurflo pump in the forums and that there would be plenty of anecdotal evidence to show its use.

So now I am faced with the concept of either waiting till Monday, when the sap will start flowing again, to talk to a technician and get consideration of what my issues are, or try to order a new one to have something in place so that I can get my lines working up to par this week.

Pull the head off to check the diaphragm. I am still thinking that there might be something stuck in there causing leakage. It is a pretty easy fix if that is all it is... Just saying... I also assume you have checked that the prescreen filter is clean? The one pump I had that the diaphragm failed was after a few seasons.

If it is indeed the diaphragm, there are parts out there that you can replace it with. In case you strike out with your seller.

That's next, pending my discussion with the tech at pentair.

Well today I got a reply from the original seller stating he would stand behind the pump and my expectations. We exchanged information for a replacement pump.

I think the check valve might be stuck