Submersible pump in cistern mounting/installation

What is the best way to install a submersible pump in the cistern? Vertical, horizontal? How do you support it? Will the torque of start/stop cycle loosen connections if pvc is used to connect to the outlet (which is 1" threaded grey pvc)? do you clamp or mount the motor to something or is it held in place by the pipe it is connected to? Any pics or drawings would be great.
Also, I need to install another inlet into my cistern (concrete). Any recommmendation for technique and equipment.. My existing inlet came from on old spring and is a rusty pipe that I do not trust so I capped it off. Inside it looked like a clogged artery.
Thank you
Kent

If the cistern is large enough mount it vertical. If not, horizontal is fine. Big thing is to not let the pump run dry. If that is a concern, use a float to control the pump when it gets in a low water situation or a Pumptec. No attachments to the tank are required. Just tighten the fittings.

I'm no Mason so I'm not going to be much help on hooking pipes to concrete. I would simply go in the top under the lid somehow.

bob...

I'm about install a submersible pump in a cistern. We've been using centrifugal pumps and they break often due to running dry and getting wet when priming it etc.

I asked around and was told about these submersible pumps. I will pick it up tomorrow but I'm not sure how to install it, does anybody has a picture of a finished installation so I can get an idea?

Valveman
Excellent suggestion about installing a flow inducing shroud over the motor and the intake. A lot of people don't realize that when a submersible pump is installed in a cistern or large tank how easy it is to damage the motor from lack of cooling. This problem is not encountered in a 4-8" well casing, of course.

I just joined this forum and I must say I enjoy reading your posts. You do seem to know your business, sir.

Bob

P.S. It would be very beneficial to these folks if you could draw a diagram or two on how to make a shroud.

I install cisterns for a living, and I would not recommend installing a well pump inside a cistern, or, if you do, I would highly recommend installing it vertically and, as Valveman said, fashion a casing in which to put the pump. If you install a standard well pump horizontally, it will create uneven wear on the motor bearings, and the general rule of thumb is that a horizontal position will cut the life of the pump in half, and every angle between 90 degrees and 0 degrees will decrease the life of the pump proportionally (90 degree mount being the longest life point). They now make pumps that are submersible and specifically designed for cisterns, like the Franklin C1 Cistern pump (stick with the 10GPM model because the 20 GPM models are designed for low head pressure and won't work for household use) or the Grundfos SBA pump. Hope this helps future readers!

Glad to hear from you cityfarmer. There is a lot of reading you can do on this subject here. There are several of us with a lot of pump experience. I wonder if you have had any problems with submersibles installed horizontally, or if like a lot of people you were just told not to do it and haven't tried it?

I have installed many hundreds of submersibles up to 75HP this way, and have never had a problem. I don't see how gravity can have much effect on the impeller stack and rotor when the pump is spinning 3450 RPM? Kind of like holding a gyro, so the bearings don't wear out. I would agree that starting with no head could cause an upthrust condition, but when using a 40/60 switch, that would only happen the first time you turn the pump on. From then on it starts against 40 PSI or 92' of head.

You are right a flow inducer is very important in cisterns, lakes, and large diameter wells.

I am also not having any luck with the new submersibles that have a bottom intake made for cisterns. A smaller diameter motor and bearing are used to be able to pass water along the side. I think this maybe one reason they are short lived. I am getting 2-3 years max, while the regular well submersibles are lasting 15-20 years.

Interesting Valveman -- I'm glad to have the push-back! Have you used Franklin's C1 bottom intake pump? I've put in about 100 of them and have not had a single failure yet, but I admit that they just came on the market 3-4 years ago (at least that's when I became aware of them) so haven't been able to see yet how they stack against a regular well pump. As for the bearing wear, that was told to me by two different technicians -- one who worked for Franklin and the other who worked for Xylem/Goulds. Maybe that's a common misconception, but I took them at their word since they're the ones dealing with testing their pumps, warranty claims, etc. On the other hand, though, I've seen several old cisterns with horizontally-mounted well submersibles that had held up for years (many of which didn't have cooling sleeves/casings around them), so you have a point.

In terms of water quality, I would argue it's best to keep the pump vertical. Too many of the horizontal mounts leave the intake way too low, so low that the pump's sucking from the anaerobic zone at the bottom of the cistern. And yes the Franklin C1 pump has a bottom intake, but it also rests on a 6" base, so the intake is still at least 8" up from the tank bottom, above the anaerobic area. Pumps like Grundfos' SBA have a floating intake, creating the best of both worlds by having a pump that was designed for cisterns (i.e., bottom suction without needing cooling sleeve) and having an intake filter that floats with the water level, drawing from the middle of the tank where the water is the cleanest. Just some more food for thought. Thanks for your quick push-back and reply, and glad to be on the forum!

100 is a pretty good test. If 90+% of them are still running after 10 years, I would start having more faith in them. But I don't think that is going to happen. It might for rain harvest and cistern pumps, as those are usually lightly used systems anyway. I mean how much rain can you collect in a year and how often do you use it? Even pumps in cisterns with low producing wells are lightly used, as it is a low producing well to start with.

Technicians at Franklin and Goulds only know what is on the troubleshooting charts. The head engineer for Goulds several years ago at a trade show told me, "he had no idea the amps would drop that low when restricting with a valve". He came over to argue with me about saying a CSV saves as much energy as a VFD. But I had a working demo at the show and he couldn't argue after seeing it for himself.

I butt heads with those "technicians" everyday. They have been instructed to say that a CSV is hard on a pump and waste energy. So I have to straighten them out on a regular basis. Every few years they get a new batch of technicians, and I have to start all over again. They want so badly for people to not use a CSV, as it is disruptive to their cash flow, as it actually makes pumps last longer and use smaller tanks. They will push the variable speeds and tankless controls as they shorten the life of the pump and fall in line with their planned obsolescence.

I do my testing on heavily used pump systems, usually in the south. Some of these wells are used for multiple applications like for a house, an irrigation system, livestock watering, etc., and sometimes all at the same time. Chicken farms, cattle feed yards, golf courses, and green house operations are very hard on pumps and make a good test case. On these type systems the tankless units and VFD's don't last very long, while the CSV eliminates any cycling and greatly extends the life of the pump. Since the CSV makes the pumps on these heavily used systems last 3-4 times longer than normal, they would probably make a lightly used cistern pump last forever.

Also if you make a cradle out of a couple pieces of PVC pipe, you can hold a horizontally installed sub off the floor any height you want, by using different size cradle pipes. This one is a good example except that the pump needs a shroud.

valveman said:

Also if you make a cradle out of a couple pieces of PVC pipe, you can hold a horizontally installed sub off the floor any height you want, by using different size cradle pipes. This one is a good example except that the pump needs a shroud.

Click to expand...

If somebody makes one of those with the shroud/flow inducer, it would be nice if they posted a good photo of that.

I have a cistern with a horizontal submersible pump (Franklin 3/4 hp 15 gpm). I did use a piece of 4” pvc which I cut a couple of v shaped pieces out longways on one end clamped it down with a hose clamp to the pump to force water over the motor. It sits directly on the bottom of the tank...somewhat, it is an underground tank so it does have ribs that sit lower than the pump but it really doesn’t make much of a difference. It has been in there for 10 years now feeding a family of 5 with no problems.

See Cary's pics here https://terrylove.com/forums/index.php?threads/submersible-pump-in-cistern.71530/#post-528624