Pump Won't Prime--Help!!

[Ray]

We live on the banks of a river, and use the river water, during the summers, to water the lawns and veggie garden. I've been doing it for 35 years. So, a couple of days ago, I hauled the pump and pipes down the river bank once again, then hooked everything up as usual. But, when I tried to get it all going, I discovered that I can't get it to prime. Now, two days later, I'm out of ideas. The foot valve is new, and seems to be working fine; at least I know that it moves freely & easily, without leaking any water. And, after filling the whole system with water, then looking into the end of the output pipe, the water just sits at the top, so I know the footvalve isn't leaking at all.

There are two splices in the pipe, between the pump and the river, but those seem to be tight. There is no water leaking from either one, even when I fill the pipe, then twist and bend it this way & that.

The pump hums along fine, when the switch is thrown, so I know the motor and pump, itself, are spinning freely.

I filled everything with water, using a hose that is connected to the house's water supply. All of the hoses (both input/suction-side and output/garden-lawn side) are full of water and feel heavy, when hefted.

Thinking there must be an air bubble somewhere, I lifted the suction/input hose high in the air, starting from the pump and working back toward the river, hoping to move the bubble up to the pump, itself.

When I fill the system with water from the house garden hose, then switch the pump on, there is an initial surge of water that comes out, but it only last for a couple of seconds, before dying out. Then the pump just hums away, with no real pumping action.

I'm now out of ideas. It's the same equipment that has worked for me all along, so it's not a matter of poor design or anything like that.

Any ideas as to what I should try next? I'm stuck and can't think of anything else to try.

One thing that I was considering: even though I don't have any water leaking out, maybe I really do have a suction leak in the suction/input hose splices between the pump and the river, but just can't tell. I was thinking of trying to seal the joints with hot glue. Would that work, or is it a crazy idea?

 

[lemuzz]

You say you get an initial spurge of water after filling the pump and line with water. This suggests the impellor is turning with the shaft. You either have a vacuum leak on the suction side or a blockage in the suction line (assuming it's an impellor type pump) If a piston type it maybe a valve or a blockage or vacuum leak. Check all joints above waterline and and if you can't find anything replace all washers etc. where air can get in. And check that there no object lodged in the suction line or weeds etc. covering the strainer. Pump problems are mostly because of air entry in the suction line

 

[speedbump]

I agree, the impellers turning and it's probably an air leak. You didn't mention what the suction line is. Is it poly, pvc or something else? What kind of fittings are there between the pump and footvalve? What kind and brand of pump? Is it also 35 years old?

 

[lemuzz]

I have seen the vanes on a impellor type pump nearly worn away, due to stones being picked up but if it was being used before being stored this is unlikely. Try the gland where the shaft enters the pump casing and repack if necessary or maybe just tighten if there is sufficient packing to allow this.

 

[Ray]

Thanks for the response, guys. Well, let's see if I can answer your questions. No, the foot valve screen isn't plugged. I pulled the foot valve back out of the river, to check it. and it's nice & clean.

I'm using the black, flexible, polyethylene pipe which has been slid over a plastic, barbed coupler, at each joint, then tightened with those silver pipe clamps that tighten up with a small "worm-gear" screw (don't know how to describe it). The pump is a Gould jet pump (impeller type).

 

[speedbump]

If you didn't warm the Poly Pipe before putting it on the barb fitting, you should. It seals much better when it's soft. I would also use a metal barb fitting, not the plastic ones. Use two clamps on each one.

Another rather strange thing I have seen happen with jet pumps that are used in lakes. Snails can get into the pump's impeller volutes. Grow to the point that they are stuck in the volutes. This takes away from the vacuum and pressure capabilities of the pump.

 

[Ray]

Well, the problem's solved! But don't ask me how, because I didn't do anything more to it. Yesterday, I went out there with the intention of pulling the foot valve out of the river, unhooking everything, checking the hoses for blockage, tearing the pump apart to inspect it, etc. I was pretty discouraged, facing all of that after two or three days of no progress. Then, before starting, I thought I'd just try priming it one more time. Then the negative thought crossed my mind, "Why try yet again? I haven't done anything different, so if it wasn't working last night, it sure as heck won't be working this morning." Then the thought, "But then you never know..." occurred, so I filled it yet again with water, switched it on, and it fired right up, gushing water out like a true champion! Too weird. The only thing I can think of was what you said, Speedbump, when you mentioned heating the poly pipe. It got pretty warm, yesterday, so the pipe joints had lots of time, sitting in the sun, down along the river. Maybe they softened enough to form a good seal, allowing it to prime; however, I didn't tighten any of those clamps, so I'm a little skeptical about that idea. Dunno. Whatever it was that finally worked, I'm not arguing. It was great to be able to be able to turn the water on and just let'er run, with no expense involved. Thanks for all your help. You guys are great.