Suction Lift Install Guide
A suction lift install is any pump that sits above its water source and has to pull the water up to itself. The practical ceiling is 6 to 7 metres of vertical lift, and it only works with a self priming or jet pump, a 32 mm minimum suction line with every joint airtight, and a foot valve at the bottom that stays submerged.
Get any one of those wrong and the pump loses prime. This guide walks the whole install, from working out your lift through to the commissioning hold test.
The short answer
Measure from the lowest expected water level to the pump centreline. 6 to 7 metres is the ceiling, less at altitude.
Self priming or jet pump only. Over 3 metres of lift we recommend a jet pump. Over 7 metres, go submersible.
32 mm minimum, short, continuously rising, airtight, with a foot valve and strainer submerged at the bottom.
Quick guide
- Maximum practical lift is 6 to 7 metres
- 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
Before you start
Read this first
These pumps will not lift reliably beyond 7 m from the surface of the water source. A submersible pump or bore pump is required for greater than 7 m lift.
Jet pumps are among the noisiest house pumps. Think about where you put it before you plumb it in.
- Read the manufacturer manual
- Isolate electrical at the switchboard, or unplug everything
- Turn off valves (taps)
- Put together a full list of the parts you are going to need, so you are not making three trips to the hardware store
- Measure twice, cut once
How high can a pump actually suck water up?
For most house pumps the practical limit is 6 to 7 metres of vertical lift, and that assumes a short, well sized, leak free suction line.
Altitude eats into that, because suction lift runs on atmospheric pressure and there is less of it the higher you go. Subtract roughly 1 metre of available lift for every 1000 metres of elevation. On most New Zealand house sites that barely moves the number, but it is worth knowing on a high country block.
Work out your vertical lift
Measure the vertical distance from the lowest expected water level, not the current water level, up to the pump centreline. If the measured lift plus friction headroom is at or above 7 m, you have the wrong setup.
Drop the pump, change the pump, or set up a submersible.
Which pump do I need for the lift I have?
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. The pumps we sell that suit suction lift work are the self priming Davey Dynajet and Grundfos JP ranges.
| Vertical lift | What to use |
|---|---|
| Under 3 m | Use a self priming or jet pump. Plenty of pumps in our house pump range are flooded suction multistage units built to sit below the water, not above it. They will hold a prime you give them, but they will not pull it back once it is lost, so we do not recommend them for lift of any depth |
| 3 to 7 m | Jet pump. Their design allows them to lift better and handle more air, so this is the right call whenever you need real lift |
| 7 m and above | Wrong setup. Drop the pump, change the pump, or go to a submersible or bore pump |
Where should the pump sit?
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 have made a big investment in your new pump, so install it in a pump shed, lean to, or weatherproof enclosure.
Most pumps are reasonably weatherproof, but they do not like rain or sun. The controller especially. Direct UV degrades plastics, and driven rain works its way in over time whatever the IP rating on the box says. If you are installing outdoors, fit one of our Davey pump covers.
Service clearance and ventilation
Leave 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. Pump motors generate heat and need to be vented.
How do I set up the suction line?
Sized to spec
Suction lift wants a bigger bore than flooded suction. 32 mm is the minimum on most house pumps. Smaller suction line costs you flow, adds friction loss and pushes the pump towards cavitation. Going up a size is safer than going down.
Short and direct
Every metre 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, because a high point is an air trap. 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 let air into the suction line, so the pump loses prime over time and you are stuck repriming it constantly.
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. On drinking water lines, check that the solvent cement and the sealant you use are rated for potable water.
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, because debris on the seat means the foot valve will not hold prime, and it keeps that same rubbish 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
A priming tee will make your life much easier later on, because it lets you fill the suction line without pulling anything apart. A priming tee with a ball valve and a funnel, at the high point near the pump inlet, is the easiest way to do it.
What goes on the discharge side?
Pressure switch or controller
Electronic pressure controllers and variable speed pumps have the pressure logic built in, and most include dry run protection that shuts the pump down when it loses flow. Treat that as a backstop, not a substitute for priming the pump properly. Check the pump before you buy, because most variable speed pumps are flooded suction units and will not lift at all. The DAB Esybox is self priming, so it is the one from that group that suits a suction lift install. You do not need a separate pressure tank with a variable speed pump, though a pressure tank is still beneficial.
Discharge side valve
Fit a valve (tap) on the discharge side so the house can be isolated from the pump without draining the system. It makes servicing easy, and it is the fastest way to work out where a leak is when the pump starts cycling for no obvious reason.
Do I need a pressure tank?
Most modern pump setups do not need an extra pressure tank. Some of the variable speed pumps we sell, like the DAB Esybox and the Davey DynaDrive, have a small pressure vessel built in. Others, including the Davey EvoDrive, do not, so check the spec of the pump in front of you. And when you use a smart pressure controller like the Torrium or the PM Start, the controller cuts out most of the rapid cycling a pressure tank would otherwise absorb. It does not remove it entirely. A dripping tap or a small leak will still cycle the pump.
That said, a pressure tank has real benefits and can be added to any pressure system:
- It cuts pump energy use, because the pump starts less often and stops running up for every small draw
- The pump turns on less often, because the tank holds a drawdown volume that covers small draws first. On an 18L Davey Supercell that drawdown is about 6.7 litres, so roughly a third of the tank, and it shifts with the precharge and your cut in pressure
- It reduces water hammer and vibration through the plumbing, because the air charge behind the tank diaphragm expands and contracts as pressure shifts
We recommend installing an 18L Davey Supercell on any pressure system that uses a pressure switch or controller. Bigger is better.
What pressure should the pump be set to?
Most house pumps are set up so they will not deliver dangerous pressure into the house. Plenty of town supply houses have a pressure limiting valve fitted somewhere, but do not assume yours has one, especially on a private pump supply. Find it or fit it before you set the pump pressure. 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 most 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, whether that is the pump, the filtration housings or the downstream pipework, fit a pressure limiting valve upstream of those components. For filtration housings specifically, anything above 500 kPa upstream needs a PLV.
Plumbing rules that apply to the whole install
Use thread tape or thread sealant on threaded joins, but never on O ring or washer sealed joins
Thread tape (PTFE) or a liquid thread sealant, and sometimes both, goes on any threaded join. The exception is joins that seal on an O ring or a flat washer, like union nuts and camlocks, which get nothing at all, because tape there stops the seal seating and causes the leak it was meant to prevent. Hose tails are their own case: they take thread tape on one side only. 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. The wrap has to run the same way the fitting screws in, so tightening pulls the tape down onto the thread instead of unwinding it. 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.
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 cures firm, so the join stays sealed better over time, especially when there is movement or water hammer in the system.
O-ring or gasket? No tape
There is one place you do not use thread tape or sealant: when the fitting has an O-ring or gasket doing the sealing. Unions where the pressure controller meets the pump often work this way.
These connections do not want tape or sealant. Adding it usually causes a leak.
Thread to thread? Always tape
Every metal or plastic thread that seals against another thread gets tape or liquid sealant, no exceptions.
No dry running
Prime the pump before first start. That means filling 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 covered below. Every pump, including the ones sold as self priming, needs 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.
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 carry their own weight instead of 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.
Electrical
Surge protection
Voltage spikes are a common cause of dead controllers on pumps. Some pump systems also include delicate electronics, so although it is not required by warranty, it is cheap insurance for a brand new piece of kit. We sell surge protectors in our online store, and your local Bunnings or Mitre 10 will stock these cheap pieces of kit too.
Water and electricity do not mix
Most pumps are designed for at least a little moisture. To extend the life of your new equipment, it is always best practice to have the system well protected by a pump cover or installed out of the elements. Pumps exposed to the weather have motor and controller issues more often, and need replacement motor bearings more often, than those that are well protected.
Most of the products we sell are plug and play. Anything beyond plugging it in is an electrician's job. That means any hardwiring, any change to the pump circuit or the switchboard, and anything that involves opening the pump or controller electrical enclosure. Do not do that work yourself and do not work on a circuit that is still live. The pump circuit should also be RCD protected, so get your electrician to confirm that before you commission the pump.
How do I prime a suction lift 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 and voiding warranty, and it still will not pull water up the suction line on its own.
Self priming pumps still need an initial prime
A common misconception is that self priming pumps are fully self priming. That 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 the wet end of the pump. They cannot prime themselves from completely empty. The first time you commission, fill the pump body and suction line manually before energising.
Repriming
If the pump loses prime, whether the suction line drained while the pump was off, the foot valve failed, or the water source dropped too low, you have to reprime. Same process as the 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.
Commissioning: starting it for the first time
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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.
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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 wet end 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.
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Open the discharge and flush downstream
Open the discharge valve. Open a tap at the house so air and new water can travel through the system.
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Energise the pump
Power on the pump. It should start and push water through the system to the open tap at the house.
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Watch the pressure cycle
Close the valve on the outlet of the pump. Pressure should rise to the cut out setting and the pump should stop. Do not leave a pump running against a closed valve. If it has not stopped within about 30 seconds of reaching its maximum pressure, open the valve straight away and find out why before you go further, because a deadheaded pump heats the water inside it fast and will cook its own seals. Once it has cut out, open the valve again. Pressure will fall and the pump should restart.
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Leak check
Turn the tap off at the house. With no water being used, the pump should pump up to pressure and turn off. Spend some time going over every new connection point and every piece of pipework to make sure there are no leaks. Even a small leak will have the pump cycling on and off, and that means early wear.
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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, which shows up as a slow start, a rough sound, or a slow pressure rise, the foot valve is leaking or there is a leak on the suction side.
Talk to us
Stuck mid install? Call and a real person answers the phone. A photo and a question by email works just as well.
Or come and see us: 65 Kenny Street, Waihi, Monday to Friday 8 to 5. 74 Kopu Road, Kopu, Thames, Monday to Friday 8 to 3.
