Sudden very slow pressure tank filling

[HMonk]

I collect rain water which I treat and then store in a 550 gallon tank. From the tank there is a 1-1/4-inch 5-foot riser and then a 20-foot straight run to my pump house (houses filters, UV, pump/pressure tank). The pump is a Sears 1/2HP shallow-well pump that has operated flawlessly for four years mounted on a 39 gallon pressure tank at 40psi with a 40/60 in/out switch. On average, the pump cycles once every 3 days.

Notwithstanding insulation (R-19), the recent record cold temps in the SW, for the first time, caused the insulated tank-to-pump line to freeze and fracture the couplings/elbows/valves, i.e.., the more rigid components (the pump house is heated so no issues there). I replaced all of the cracked components, pressurized the line to r/o hidden fractures/leaks, verified the tank charge/pump prime and restarted the system. It took the pump <10 seconds to run the pressure from 0-40psi. However, at 40psi, the pump continued to run but the pressure did not increase.

I disassembled the pump and a quick inspection revealed no obvious defects. I reassembled the pump and, as before, it quickly pressurized to 40psi, stalled, for a minute or so then slowly rose to 60psi over about 5 minutes.

Maybe I missed something? I again disassembled the pump and noticed that in separating the pump head halves there was a rather weak frictional fit between the venturi o-ring and the walls of the diffuser port – as if the o-ring had lost its resiliency (to look at it the o-ring is in perfect condition). This time I very carefully inspected all of the components: jet, venturi, diffuser plate, housing, pressure gauge, check valve: all seemed to be in perfect condition. I intended to replace the venturi o-ring but it’s an odd size so I had to special order it.

Referring to the attached JPEG: the venturi (12) has an o-ring (11) at its end. This is inserted into the diffuser plate (8) which feeds water to the impeller (7). So what I am wondering is: if the o-ring does not furnish a tight seal, would the pressurized water blow back by the ring and somehow compromise the water flow to the impeller - thus causing the tank to pressurize more slowly?

Grasping at straws and while waiting for the new o-ring to be delivered, I made a few Teflon tape windings in the o-ring retention groove on the venturi thinking I could effectively increase the diameter of the o-ring and increase its pressure against the diffuser plate. I reassembled the pump, re-verified the tank pressure, primed the pump and turned it on. As before, the pump quickly pressurized to 40psi but continued to pressurize to 60 psi over the next 3 minutes, i.e., there appeared to be some improvement. As of now, it continues as above: on at 40psi, off at 60psi taking about 3 minutes to get there. This pump delivers about 8gpm and, attached to my 39 gallon pressure tank, it usually cycles after approximately 12 gallons have been drawn from the tank, taking a minute or less to repressurize. It now takes 3 times as long.

Since the pump house is heated, I have to conclude that the cold weather did nothing to compromise the pump. There is no air in the water so I have to conclude that there are no leaks in the supply line. As a further check, I removed the tank shrader valve thinking that, if there was water in the tank due to a punctured bladder, I might observe water/mist being expressed from the tank. Nothing.

While I am very experienced in plumbing installations and operations, I have never had the occasion to TS well pumps so much of my conclusions are intuitive, in part based on what I am able to discern from researching the issue.

So, I have two questions:

1. apart from the o-ring, if we assume that pump components (jet, venturi, diffuser, impeller) are not in any way defective, regardless of my findings, does anyone have a notion of what might be some of the possibilities to explain the pump’s suddenly taking so long to pressurize the tank, i.e., the most likely cause is this, the next most likely cause is that, etc.?

2. if we were to assume that the o-ring could contribute to the issue, while I am waiting for the new o-ring to be delivered, does anyone know of a “trick” that can be employed to temporarily effect increased o-ring pressure, perhaps by partially filling the o-ring retention groove as I have or by some other means?

Thanks, Monk

 

[speedbump]

The fact that the pump jumps to 40 psi so fast is because you have 40 psi in the tank. There is nowhere for the water to go unless you have a valve open. Once the pump gets over 40, the tank will start taking in water.

As much as I dislike those plastic pumps, it should still produce more water than what your getting.

You might take a peek at part #14. If your pump ran dry for any period of time, I have seen that plastic piece that aims the nozzle at the venturi tube warp from heat. This will affect your top pressure and the pumps volume if the nozzle isn't hitting the venturi dead center.

I doubt that the O-ring has anything to do with your problem.

 

[HMonk]

Thanks Speedbump: your explanation of the 0-40psi jump is common sense that eluded this old man!

The last time I disassembled the pump, I removed everything from within the pump head and very carefully inspected it. The jet (#14 on the parts list) is a simple enough 5/8-inch plastic nut that is funneled down to an approximate 3/8-inch opening; overall it extends approximately 1/2-inch from its seat. I am able to say that, at least to the naked eye, it is flawless: not cracked, chipped, warped or deformed in any way; so too the venturi, diffuser, and impeller. This is not to say it is not the source of the issue; I simply cannot detect any defects. When I look at the jet from the end of the 4-inch venturi, at least to my eye, it appears to be a straight shot.

According to the install manual, given a 1-1/4-inch inlet and a 1-inch outlet (which is what I have), at 40psi, and a 5-foot pumping depth, this 1/2hp pump should deliver 8.2gpm. Nothing has changed about my installation which has a 5-foot riser adjacent to the tank which is about 4-feet high (so the riser is full to a point of 3-4 feet as I continually top off the tank) which then leads to an essentially horizontal, 20-foot run to the pump. Given these dimensions, I figure that the water has an unimpeded flow to the pump.

Given my limited experience with well pumps, intuitively/logically, it seems to me that water is either not being delivered to the impeller in an adequate quantity/rate - or - water from the tank to the pump is being impeded. When I replaced the cracked pipeline components, I used a typical pvc pipe cutter which caused the pipe to shatter in a couple of instances. While not likely, I am now wondering if a chunk of pipe flew into the pipe and is now lodged in such a fashion as to impede water flow. I doubt this because when I replaced the crack fixtures, the supply line contained a 1-1/4-inch diameter, 20-foot long icicle, i.e., no place for a chuck of pvc to go.

When the weather warms a bit more, I intend to reroute the supply line under my house where the temps did not get below 35 degrees during the extreme cold snap (Given the presence of insulated but otherwise exposed water lines, I monitor the crawl-space temps). Rather than salvage the existing line, I plan to run an entirely new line which, of course, will answer the question of supply line blockage.

Given my lack of experience with TSing well pumps, I am stuck in an intuitive/logical mode which, on the surface, seems to have ruled out the usual suspects.

Finally, I have read a number of articles that generally condemn plastic pump heads; oddly, few offer their reasons for doing so, so my knowledge in this area is lacking.

I will post back after I replace the o-ring (next week) and reroute the supply line (probably late March).

Thanks for your interest,

Monk

 

[speedbump]

If your flow chart says 8gpm @ 40psi, then it's working like it should. I just thought a 1/2hp pump should do a bit more.

The main reason I don't like plastic pumps is the noise they make. They sound like they are worn out fresh out of the box. They are just too darned noisy. The second thing is their chinsie backpressure control on the deep well models. They could have left it off for all the good it does. Thirdly, they don't like heat.