Jet pump not building pressure

[saltyOldDog]

Curious if anyone knows better.
I have a new burcam 506538ss (https://www.waterpumpsdirect.com/Burcam-506538SS-Water-Pump/p7695.html). 3/4hp shallow well jet pump.

There's a new foot valve in the lake about 100m away with a filter sock on it at a depth of about 6'. The intake line is 1" black poly that runs underwater about halfway and underground the other half. It comes into the basement through the wall, so the grade is at most a few feet. I have a check valve, then a length of braided reinforced pvc into the pump intake, and another length of braided pvc from the pump outlet into the pressure tank.

The pump pulls water with very few if any bubbles in the intake line, but does appear to push more air into the outlet than comes in through the inlet.
When I first set it up, I had it primed with enough water that it was able to pull whatever air was still in the intake line and worked beautifully.
Then yesterday the pvc threaded fittings on the intake and outlet both failed weirdly, like they warped and sheared the threading, so those have both been replaced with a brass intake fitting and a stainless steel outlet fitting.
Right now, it builds to 40psi and never hits the 50psi cutoff.

There's zebra mussels in the lake, which is why we had to go redo the foot valve last summer and put the filter sock on. When I redid the system with the new pump last week, I found fragments of zebra mussel jamming the check valve open. My two prevailing theories right now are either a) there's more gunk clogging the check valve, b) there's more gunk clogging the venturi inside the pump. The intake line being braided hose isn't my first choice, but it's what was available until I can get either a length of poly or a flexible suction line hose. The intake line does collapse somewhat while the pump is running, but it still pulls water through. Maybe the diameter is choking off the water too much to feed the centrifuge? It wasn't a problem at first so I'm not sure why it would be a problem now. When the pump is off, the pvc intake hose goes perfectly round.

I can take it apart up to the point of looking inside the pump, but I haven't gotten familiar with how to check the venturi for clogs. What are the odds it's the venturi vs the check valve?

 

[Valveman]

When plastic pipe or fittings connected to the pump warp, the pump got hot. Usually a suction leak causes the pump to loose prime, run dry, and melt fittings. Once a pump has gotten that hot it may never build to 50 again. You could also still have a suction leak, but most likely the impeller melted.

As long as it is running on 230V a Cycle Sensor will work with a jet pump just as well as with a submersible. It will protect the pump from running dry by shutting it off when the amps get low.

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[Reach4]

There's a new foot valve in the lake about 100m away with a filter sock on it at a depth of about 6'. The intake line is 1" black abs that runs underwater about halfway and underground the other half. It comes into the basement through the wall, so the grade is at most a few feet. I have a check valve, then a length of braided reinforced pvc into the pump intake, and another length of braided pvc from the pump outlet into the pressure tank.

The pump pulls water with very few if any bubbles in the intake line, but does appear to push more air into the outlet than comes in through the inlet.

The black pipe is probably polyethylene.

You could check for vacuum leaks by slathering accessible joints, including the input to the pump, with shaving foam. Run the pump. See if the foam gets sucked in anywhere.

https://www.waterpumpsdirect.com/manuals/burcam-77804514b6fd39bb70c7e15b3d84612d.pdf

I don't see an access to clean the nozzle without removing the housing. Some pumps have a plug for the purpose.

 

[Chucky_ott]

I agree with Valveman that your pump likely ran dry and melted the PVC fittings.

You should not have the check valve at the pump. The only check valve should be the foot valve. The second check valve at the pump may be preventing the foot valve from closing properly. When the pump is not running, water will flow out the foot valve and this could cause a vacuum in the intake pipe. This will then suck in air from any of the joints.

If mussels are are big problem, you could consider a sand point.

 

[Bannerman]

Further to Chucky's comments, the use of the upper check valve maybe resulting in water hammer, which maybe a further cause of the connection failures.

Removing the upper check valve will cause the suction line to become pressurized by the pressure tank while the pump is not running. This will not only assist the foot valve to fully close, thereby reducing the potential for loss of prime while the pump is not operating as already stated, but also reduces the potential for water hammer occurring.

 

[saltyOldDog]

Thanks everyone for the advice. I've removed the check valve and replaced the braided pvc with a length of black pipe I'm pretty sure is abs. I'm going to try putting something over all the interior connections to see if there's a suction leak inside. I'm guessing part of the not building pressure might have been cavitation from the resistance caused by the check valve being there.

The original reason for the check valve is last winter we figured out that there must have been something jamming open the foot valve which we couldn't do anything about with the lake ice overtop of everything. For decades the house had been hooked up with these old piston pumps which have a tendency to leak, tear through leathers, make noise, chew through power, etc, but despite all that they were able to build crazy pressure. The idea of moving to a jet pump is because they've been standard everywhere I've ever lived. Just worked, never issues.

Now with the check valve out, I noticed when priming the pump that it would just keep taking water, not quickly but it would keep taking it quick enough that you had to close everything up and give it power to give it a chance to draw water. In addition, after it reached cutoff (I turned the on/off down from 30/50 to something closer to 20/40), I could see a slow reverse flow in the braided line, so this makes me think there's either something else wedging the foot valve open, or a break in the line underground. In concert with drawing air, that could either be a leak in a fitting, or also a break in the line... So I'm thinking a break in the line underground?

Once a pump has gotten that hot it may never build to 50 again. You could also still have a suction leak, but most likely the impeller melted.

I had a look inside the inlet and outlet ports. Everything I could reach seemed solid still. How could I check if there's pump damage vs intake leaks.

 

[saltyOldDog]

Tried the trick with shaving cream and plastic wrap. No sign of a suction leak on any of the fittings inside the house. It still drains backwards after stopping the cycle. I have it turned down to 15/35 and it hits pressure OK. I'm going to gradually step it up to see if it hits higher pressures ok. I know it can't hit 50 right now.

I'm pretty sure it's never run "dry" even when the plastic fittings failed, because there's always been water in the outlet available to drain back into it. Even when it's pulling air bubbles, it's still pulling water. Digging up the lawn is going to be a big job if I have to replace that line... We might sit on this line for the winter and then run a line over the lawn in the summer to test the theory that the line has a leak under the lawn. I know it's not one continuous piece because there's splices in the line in the water... I don't know if when they installed it, they may have put splices in the line in the part that's under the lawn.

 

[saltyOldDog]

FWIW, I would prefer to install a submersible, but people are skittish about the possibility of electrical leaks into the lake and liability that could come with. If there was a way to put the submersible in a well or reservoir that's gravity fed from the lake, could that work?

 

[Chucky_ott]

That pump is supposed to reach 70psi so if it can't even do 50, there's something wrong with the pump, the gauge, or both. As Valveman stated, if it got hot enough to melt the PVC fittings, it probably got hot enough to melt the impeller. Only way to know would be for you to disassemble the pump. I don't know if a blocked venturi can cause pressure issues with pressure. Maybe someone with more knowledge can chime in.

Running dry doesn't necessarily mean there was no water in the pump. But there was enough air to make it lose prime. Eventually, whatever water you have in the pump will turn to steam. It's happened to me twice where the PVC fitting on the discharge side melted. I eventually installed a pressure switch with a low pressure cutoff AND a temperature relief valve (TRV). If the temperature gets too high, the TRV will open, the pressure will drop below 20psi, and the cutoff will stop the pump. A manual reset is then required.

A better solution would be a run-dry sensor like Valveman suggests, but it only runs on 240V, which I don't have yet.

 

[Chucky_ott]

. It still drains backwards after stopping the cycle.

If you shut of power to the pump after it reaches your 35psi (or whatever the cutoff is), does it eventually go down to zero ? If it does, you have a leak somewhere. Without isolation valves (just regular ball valves), it might be hard to figure out where. Post a picture of your setup if you can.

For testing, I have a ball valve just downstream of the pressure tank (i.e. between tank and house). Closing that valve will tell me if I have a leak anywhere in the intake pipe.

 

[saltyOldDog]

If you shut of power to the pump after it reaches your 35psi (or whatever the cutoff is), does it eventually go down to zero ? If it does, you have a leak somewhere. Without isolation valves (just regular ball valves), it might be hard to figure out where. Post a picture of your setup if you can.

For testing, I have a ball valve just downstream of the pressure tank (i.e. between tank and house). Closing that valve will tell me if I have a leak anywhere in the intake pipe.

Most of this is intended as a temporary solution until I can replace the old stuff. The check valve is no longer there and it doesn't make the same sound as it did before. There's still a noise when it starts up but that quiets down pretty quick. It struggles to break 37psi, but that's enough to run the faucets. The rodi and shower are the most sluggish. There's a sand filter and 2.5x10 5micron filter downstream. I'm replacing that with a 50micron spindown and a 4.5x20 5micron. If the sand filter is problematic then that might come out too. I need to figure out if I can put pressure gauges after each filter. Apart from when it starts running, you can't see any air coming up the braided line. There's a bubble that hangs out in the top of the loop which gets pushed down into the bottom part of the loop while it's running at low pressure and eventually returns to the top when the flow slows at higher pressure. After it hits cutoff, you can see the reverse flow pushing the bubble back toward the pump. Not enough to take it away from the top part of the loop, but enough to see a consistent flow that agitates the water in there. I'm going to shorten the discharge hose when the new tank goes in, but for right now it handles the change in direction and helps with priming. My plan for the reverse flow is to use that air line that connects to the drain valve in between the two tanks to hook up an air compressor at a safe target pressure and run it continuously while the system is closed, then go for a swim and verify if there's bubbles coming out the intake line. If nothing shows, then that guarantees the reverse flow is disappearing into the lawn somehow... If I have to redo the intake line, I'm going to step it up to 1.25" or larger to minimize friction losses. Also after leaving the plastic wrap and shaving foam on the intake fittings long enough, I suspect it might be moving slightly at the fitting where the check valve used to be, so next chance, I'm going to depressurize everything, snug up those fittings, and add a second hose clamp.. I have plenty of worm gear clamps but they aren't the best. None of the stores around here carry the t-bolt clamps.

 

[Chucky_ott]

Not the best picture. Not sure where in Ontario you are but Princess Auto sells the t-bolt clamps.

You didn't answer this question: "If you shut of power to the pump after it reaches your 35psi (or whatever the cutoff is), does it eventually go down to zero ?". And how quickly?

 

[Reach4]

Not sure where in Ontario you are but Princess Auto sells the t-bolt clamps.

Interesting... I had not looked into t-bolt clamps.

https://www.amsperformance.com/wp-content/uploads/2016/08/Worm_Gear_Clamp.pdf claims worm-gear is better, at least for some applications. Worm gear clamps can be put on without having access to an end to slide the clamp in place.

People generally agree that T-bolt can give a stronger squeeze.

 

[Reach4]

My plan for the reverse flow is to use that air line that connects to the drain valve in between the two tanks to hook up an air compressor at a safe target pressure and run it continuously while the system is closed, then go for a swim and verify if there's bubbles coming out the intake line.

For this test, having the air precharge higher than the test air pressure would seem to be a good safety measure. That way there would be no huge blast of air in the case of a sudden leak failure.

 

[Chucky_ott]

People generally agree that T-bolt can give a stronger squeeze.

The ones I've seen have a SS band but the bolt is zinc-coated steel. Unless I find one fully SS, I'd still use the worm-gear type