Suction Lift

What it is: the pump sits above the water level, so the pump has to pull water up to its inlet. This is a harder configuration to get right and it is unforgiving of mistakes. We use it only where flooded suction is not possible. A suction lift of less than 3m a standard flooded suction pump will be okay.

When this applies: suction lift less than 7m (the vertical elevation from the surface of the water source to the suction inlet on the pump)pump in a shed above a creek or dam, pump pulling from a shallow well or borehole, or any setup where the water surface is below the pump inlet.

If you have the option to drop the pump below the water source, take it. Flooded suction is more reliable, easier to commission, and less likely to fail and require re priming.

What Pumps: Davey XJ70T, Grundfos JP 5-48

Quick Guide
  • Maximum practical lift is 6 to 7 meters
  • Self priming pump or jet pump only
  • Suction line: 32 mm minimum
  • Every suction joint must be airtight
  • Foot valve at the bottom, brass or stainless, kept submerged
  • Priming tee at the pump
  • Commissioning includes a 10 minute hold test

General

Before you start

These pumps cannot lift more than 7m from the surface of the water source.
A submersible pump or bore pump may be required for greater than 7m lift.

  • Jet pumps are the noisiest house pump
  • Read the manufacturer manual
  • Isolate electrical at the switchboard or unplug everything
  • Turn off valves (taps)
  • Put together a list of parts you are going to require, not a hardware-store-detour list
  • Measure twice, cut once
Electrical
Surge protection

Voltage spikes are a common cause of dead controllers on pumps. Some pump systems also include delicate electronics so although not required by warranty, its cheap insurance for your brand new piece of kit. We sell surge protectors in our online store but your local bunnings or mitre10 will stock these cheap pieces of kit.

Water and electricity don't mix

Most pumps designed for at least a little moisture. To extend the life of your new piece of equipment, it is always best practice to have the system well protected by a pump cover or installed out of the elements. Pumps that are exposed to the elements will more regularly have motor and controller issues and often need replacement motor bearings more regularly than those that are well protected.

Most of the products we sell are plug and play, any electrical changes you need to make should be carried out by your local electrician

Plumbing
Use thread tape or thread sealant on every threaded join

Thread tape (PTFE) or a liquid thread sealant (sometimes we use both) is required on every threaded join to stop leaks. The easiest way to remember how to apply thread tape is to hold the fitting in your left hand and wrap the tape around the thread by rolling it away from you, six to seven revolutions. Try not to get tape on the first couple of threads that slot into the female fitting, or you will end up cross threading or fighting alignment.

No dry running

Prime the pump before first start. What does that mean? Fill the suction line and the wet end of the pump with water. There are a few ways to do this depending on the install and they are outlined in the sections below. Most pumps (even the ones that claim they are self priming) need water in the wet end to run safely. Dry running for any amount of time damages seals, melts internal components, causes leaks, and shortens the life of the pump. Damage from dry running is not covered under warranty.

When to use Loctite 5331 instead of tape

Thread tape has weaknesses compared to a liquid sealant. If you tighten a thread too far and have to back off, the tape often leaks and you have to redo the join. For plastic and PVC connections we often use a liquid sealant like Loctite 5331 instead. Two benefits. You can adjust the thread as you fit the pump without losing the seal. And 5331 sets firm, which holds the thread together far better over time, especially when there is movement or water hammer in the system.

The exception: O-rings and gaskets

There is one place you do not use thread tape or sealant: when the fitting has an O-ring or gasket to seal it. Things like unions where the pressure controller meets the pump sometimes have an O-ring doing the seal. These connections do not want tape or sealant. Adding it usually causes a leak.

Quick rule of thumb. O-ring or gasket? No thread tape. Thread to thread? Always use thread tape or sealant. 

Short video example here.

Support the pipework and the pump

The pump should be securely bolted or screwed to whatever it is sitting on. That stops the pump walking under vibration, and it stops vibration travelling out through the pipework. The pump weight should never hang off the plumbing. The plumbing itself should be supported with brackets or clips so the suction and discharge lines are carrying their own weight, not pulling on the pump body.

Avoid air locks

On the delivery side, the line from the pump to the highest fixture should rise consistently. No traps. House pumps rarely run into air lock issues on the delivery side.

On the suction side, air locks cause real problems. Avoid any section of pipe where air can collect. A steady, constant gradient beats sharp turns or pipe runs that rise then drop sharply.

Pressure
Pressure tanks

Most modern pump setups do not need an extra pressure tank. The variable speed pumps we sell, like the Davey EvoDrive and the DAB Esybox, have pressure tanks built in. And when you use a smart pressure controller like the Torrium or the PM Start, the controller itself prevents the rapid cycling that a pressure tank would otherwise smooth out.

That said, a pressure tank has real benefits and can be added to any pressure system. It can save up to 30% on pump energy use. The pump turns on less often, because around 20% of the pressure tank's volume is used before the pump needs to kick in again. And it reduces water hammer and vibration through the plumbing, because there is an air bubble in the tank to expand and contract as pressure shifts.

We recommend installing an 18L Davey Supercell on any pressure system that uses a pressure switch or controller. Bigger is better.

Pressure settings

Most house pumps are set up so they will not deliver dangerous pressure into the house, and most houses already have a pressure limiting valve fitted somewhere. As a rule, do not run pressure above 500 kPa (72 psi) into the house without a pressure limiting valve in place. 300 to 400 kPa is great pressure for most households.

Some pressure controllers, and all smart variable speed pumps, let you adjust the setpoint. We recommend using a pressure controller with a built-in pressure gauge like the PM Plus, or fitting a separate pressure gauge in the system so you can see what the pump is doing.

Pressure limiting valve where the supply needs it

Separate from your downstream pressure setting: if the incoming supply itself can exceed the rating of any component (the pump, the filtration housings, the downstream pipework), fit a pressure limiting valve upstream of those components. For filtration housings specifically, anything above 500 kPa upstream needs a PLV.

Suction lIft

Before you commit
Before you commit
Check the lift limit

For most house pumps the practical limit at is 6 to 7 meters of vertical lift, and that assumes a short, well sized, leak free suction line.

Above about 300 meters altitude, subtract roughly 1 meters of lift for every 300 meters of elevation.

Choose the right pump for the job

A standard house pump generally cannot suction lift. It can stay primed if you fill it before start, but lose prime once and it will not pull itself back. Any situation where lift is greater than 3m we suggest a jet pump.

The pumps we sell that suit suction lift work are the self priming Davey XJ and Grundfos JP ranges. Jet pumps are the right call when you need real lift (3 to 7 metres or more) because their design allows them to lift better and handle more air.

Work out your vertical lift

Measure the vertical distance from the lowest expected water level (not the current water level) to the pump centreline. If your suction lift is less than 3m any house pump in our range will work but we always would recommend a jet pump like an Davey xj70t or a Grundfos JP 5-48

If the measured lift plus friction headroom is at or above 7m you have the wrong setup.

Drop the pump, change the pump, or set up a submersible.

Service clearance and ventilation

Leave some clear space above the pump for service access, and 200 mm at the rear for airflow. Do not install in a sealed cupboard with no airflow as pump motors generate heat and needs to be vented.

Pump placement
As close to the water source as the layout allows

Every metre of suction line adds friction loss and eats into available lift. Place the pump as close to the water source as the install allows, and as low as the layout allows. A pump three metres above water with a five metre suction run is far healthier than the same pump with a fifteen metre suction run.

Stable, level base

A concrete pad is best but a couple of large pavers works well. Bare ground does not. The base must be level so the pump body sits true and so the priming port (if there is one) does not leak air on the high side.

Under cover

You've made a big investment in your new pump so install it in a pump shed, lean-to, or weatherproof enclosure.

Although most pumps are reasonably weather proof, they do not like rain or sun. The controller especially. Direct UV degrades plastics, and rain ingress over time will reach the electronics no matter what the IP rating claims. If installing outdoors purchase one of our Davey pump covers.

Service clearance and ventilation

Leave some clear space above the pump for service access, and 200 mm at the rear for airflow. Do not install in a sealed cupboard with no airflow as pump motors generate heat and needs to be vented.

Suction line (from water to pump)
Suction line (from water to pump)
Sized to spec

Suction lift wants a bigger bore than flooded suction. 32mm is the minimum on most house pumps. Smaller suction line costs you flow and pushes the pump into cavitation.

Going up a size is always safer than going down.

Short and direct

Every meter of pipe adds friction on the suction side. Keep the run as short as the layout allows.

Continuously rising to the pump, no high points

The suction line should rise consistently from the water source up to the pump inlet. No high points (air traps). A steady, continuous gradient is what you want. Sag in the line that lets air collect at the top will stop the pump on the next start.

Every joint must be airtight

Even a tiny pinhole leak can result in allowing air into the suction line and losing prime over time leading to frustrating continuous re priming.

On the suction side the line is under vacuum, not pressure. A joint that holds water under pressure can still suck air under vacuum and lose prime. Use solvent welded PVC, or threaded joins with Loctite 5331 rather than thread tape alone. Tape works on pressure joints. On vacuum joints, a liquid sealant gives you a much better seal.

Foot valve at the bottom, mandatory

A foot valve sits at the submerged end of the suction line. It is a non-return valve that holds the prime in the suction line when the pump stops, so the pump does not have to repull water from the source on every start. Without a foot valve, a suction lift install loses prime every time the pump stops and you are repriming manually on every restart. Use a brass or stainless foot valve, not a cheap plastic one.

Strainer below the foot valve

A mesh strainer sits below the foot valve, submerged. It keeps leaves, sticks, and debris off the foot valve seat (debris on the seat means the foot valve will not hold prime) and off the pump impeller. Some foot valves come with an integrated strainer. If yours does not, fit a separate one.

Keep the foot valve submerged below the lowest water level

The foot valve must stay below the water surface at the lowest level you ever expect. If the dam, well, or tank can drop to a level that exposes the foot valve, the pump will draw air, lose prime, and stop. Measure your worst case water level before you size the suction line length.

Priming port or tee

This is a nice and will make your life easier in the future as you can fill the suction line from the priming port on the pump. A priming tee (with a ball valve and a funnel) at the high point near the pump inlet is the easiest way to do this.

Discharge line (from pump to house)
Pressure switch or controller

Electronic pressure controllers and variable speed pumps (Davey EvoDrive,DAB Esybox, and similar) include the pressure logic built in and will protect your pump from running dry rapid cycling etc. You do not require a pressure tank, however, a pressure tank is always beneficial.

Discharge side valve

A valve (tap) on the discharge side so the house can be isolated from the pump without draining the system for servicing but also for helping diagnose issues like identifying where leaks are in the system.

Priming the pump
Why priming matters

A suction lift pump cannot start dry. The pump needs water inside the body and inside the suction line before you energise it, because the pump creates flow by spinning water, not by sucking air.

If the pump starts dry, it dry runs (damaging seals, melting components, voiding warranty), and it will not pull water up the suction line on its own.

Repriming

If the pump loses prime (suction line drains while pump is off, foot valve fails, water source drops too low), you have to reprime. Same process as first prime: pour water in at the priming port until the system fills. This is why a priming tee is non negotiable on a suction lift install. Without it, you are taking the pump apart to reprime.

Self priming pumps still need an initial prime

A common misconception is that self priming pumps are fully self priming. This is just not the case, all the pumps we sell need water to create suction.

Self priming pumps can rebuild prime on their own provided there is a good amount of water in the suction line and wetend of the pump.

They cannot prime themselves from completely empty. First time you commission, fill the pump body and suction line manually before energising.

Commissioning

Step 1: Confirm the foot valve is submerged

Visually confirm the foot valve and strainer are below the water surface at the source. If the source can be drawn down during the test, account for that.

Step 2: Prime the pump

Open the priming port. Pour clean water in until the pump body and the suction line are full and water spills out the top. Close the priming port.

The priming port is the bolt on the wetend of the pump.

In some circumstances, you may be able to open the priming port and move the suction line up and down repeatedly to prime the pump.

Step 3: Open the discharge and flush downstream

Open the discharge valve. Open a tap at the house to allow air and new water travel through the system.

Step 4: Energise the pump

Power on the pump. The pump should start and start pumping water through the system to the open tap at the house.

Step 6: Watch the pressure cycle

Close the valve on the outlet of the pump. Pressure should rise to the cut-out setting. The pump should stop within a 30 seconds of reaching its max pressure. Open the valve again. Pressure will fall and the pump should restart again.

Step 7: Leak check

Turn the tap off at the house, if no water is being used the pump should pump up to pressure and turn off. Spend some time to go over every new connection point and piece of pipework to ensure there are no leaks. Even a small leak will lead to the pump cycling on and off and early wear.

Step 8: Hold test for prime retention

Turn the pump off. Leave it for 10 minutes. Energise it again. If it starts and pressurises immediately, the foot valve and suction line are holding prime correctly. If it has to repull water (slow start, rough sound, slow pressure rise), the foot valve is leaking or there is a leak on the suction side.

Stuck mid-install?

Call 07 863 8064 weekdays 8am to 5pm. A real person answers the phone.

A photo and a question to contact@pumpstuff.co.nz works too.