Vertical Sump Pumps- Suction Extensions

[MJCronin]

To all,

I have a question from a client who wants to re-use a vertical sump pump, but has had operation problems in the past. ( this type of pump is also sometimes called a "vertical cantilever&quot

The pump is used in a sump where an "extension pipe" is attached to the suction to enable the pump to draw down deeper to the bottom. The extension pipe is about three feet long. The client wants to use the pump in a sump that is about 18 inches deeper.

I have checked the manufacturer's catalogs and the HI standards and there is no guideance on these pipes. They are not typically offered as options ( although i found one website with a plastic pump where they were offered)

See this site for a picture:

http://www.haywardgordon.com/case_studies/CP1_VC_Ap4.html

My questions are:

- Anybody have experience/recommendations or cautions about these pipes ?

- Why dont the pump vendor's offer these ?

- What experience does anyone have with these ?

Thank You in Advance.....


MJC

 

[Lovison]

Suction pipes (often called tailpipes) can be and most do have various lengths. I would need to know your flow and head conditions to be a little more specific. A general rule of thumb I use is that for every 10' of vertical lift you should be able to pull 1' of tailpipe.

Of course this is at an ambient condition. The pump will continue to pumping down the tailpipe once priming has begun. Priming means that the liquid must get over the top of the casing to initiate a prime. After that the pump will pull down below the casing on the tailpipe.

In some case's when the liquid level reaches a certain level or depth in the sump the pump may just quite pumping. The only way to make it pump more would be to increase the pump speed.

Prime may break prematurely if there are suction leaks on the suction piping. Prime may break if the pump suction picks up a vortex. Air-entrainment will drop pressure and volumn and could also break priming prematurely.

Remember that while your liquid level is dropping in the sump so will your head pressure. Eventually the pump will break prime (where I can't be that specific) but when it does it will not prime again until the liquid level rises flooding of the casing.

Note there are devices called priming inductors which can be used to re-prime vertical pumps below their casings. These are like small booster pumps. These are connected to the suction pipe and an external water source is required under a predetermined pressure which ejects this water up into the tailpipe allowing a prime to take place.

Some even use this inductor once the pump has primed to give additional boost to increase discharge line velocities when heavy ash or solids are being displaced.

If I knew how to attach a drawing to this item I would so you could see what I'm talking about. Contact me and I will e-mail you a copy.

Wayne E. Lovison
service-parts@naglepumps.com