The water inlet node on a borehole
The whole node, as a live schematic
The schematic is built in our editor from catalogue parts and passes the same compatibility checks the app runs — turn it, switch to 3D, open the parts list. On the left is the column down the borehole, then the service entry, and on the right the automation, the filtration and the manifold.
The column is deliberately drawn separate from the well head: the head's collet clamps the very pipe that comes up from the pump; the head has no second hydraulic outlet (the second port is for the cable only), and drawing a joint between them would mean inventing a connection that does not exist.
The order, and the reason for each part
Read it as a chain: the reason column answers why the part is there at all. Anything that cannot name its reason comes out of the node — it is money, resistance and one more thing to fail.
| # | Part | Why it is there |
|---|---|---|
| 1 | Submersible pump | With the water table deeper than 8 m a surface pump cannot lift the water — that is the suction limit. Output must not exceed the borehole yield, or it runs dry |
| 2 | Check valve at the pump | Holds the column of water when the pump stops. Many borehole pumps have one built into the discharge port — check the data sheet: if it is built in, no second one; if not, fit one right at the pump outlet |
| 3 | Well head | Carries the pump on its rope, seals the mouth, passes the cable. The number after the slash is the HDPE pipe size, not inches |
| 4 | HDPE run into the house | Below the frost line and in a sleeve. Laid higher, it gets replaced after the first winter |
| 5 | Main valve | Shuts the house off — without it nothing downstream can be removed |
| 6 | Pressure vessel | Smooths the starts: without it the pump fires up for every glass of water and dies of cycling. Air in the empty vessel — 0.2–0.3 bar below the cut-in pressure |
| 7 | Pressure switch and gauge | Start and stop by pressure; the gauge is what the switch is set by |
| 8 | Dry-run protection | The yield is limited: without it the pump goes on the first drop in level. Some pumps have it built in (check the data sheet); otherwise a dry-run switch on the same five-way fitting or a level sensor down the borehole. No catalogue part for it |
| 9 | Relief valve | The second line: if the switch contacts weld shut, pressure climbs until something bursts. Set it above the cut-out pressure and below the rating of the weakest part, with a visible discharge to a drain |
| 10 | Strainer and BB20 housing | Sand from the borehole. Water treatment, if the analysis calls for it, goes after them |
| 11 | Manifold with valves | Each branch isolates on its own and no fixture starves when another one runs |
No expansion vessel here: there is no trapped volume being heated. That arrives with the water heater and its safety group.
The mistake this schematic exists for
The pressure switch must sit ahead of the filters. Put a filter before the switch and, as it clogs, the switch stops seeing the pressure behind the filter: the pump keeps running, the pressure downstream never rises, and the cut-out never comes. That is a cooked pump and a burst housing — from a filter that was merely dirty.
Half the diagrams online show it the other way round. On the schematic above the switch sits on the five-way fitting, right at the vessel, and the strainer and housing come after.
Winter and draining down
Anything above the frost line freezes in winter — and splits the pipe, rather than merely stopping the water. So the entry runs in a sleeve below the frost line, and any stretch in an unheated space is either insulated with trace heating or made drainable.
A drain cock at the low point belongs in every node — without it you cannot change the vessel's diaphragm or take the housing off. A seasonal house adds falls towards it, built in at installation: a system laid flat cannot be drained when the frost arrives.
Common questions
What is in a borehole water inlet?
A submersible pump with a check valve, the well head, an HDPE run into the house below the frost line, a main valve, a pressure vessel with a switch and gauge, dry-run protection, a relief valve, a strainer and a mechanical filter, and then a manifold with a valve on every branch.
In what order do the vessel, the switch and the filters go?
Vessel and switch right after the entry, filters after them. With a filter ahead of the switch, a clogged filter means the switch never sees the pressure rise and never stops the pump. The gauge sits by the switch — it is what you set it by.
What size pressure vessel do I need?
For a house with several fixtures, 50–100 l is the usual range: the bigger the vessel, the fewer starts and the longer the pump lives. The exact figure comes from the pump's output and the starts-per-hour limit in its data sheet: some models allow 20 starts an hour, others up to 100, and they need different vessels.
Do I need a check valve if the pump already has one?
For a typical borehole, no: a second valve adds only resistance and one more place to fail silently. Two exceptions: the pump has none per its data sheet — then one goes at the pump outlet — and a very deep installation, where the manufacturer itself asks for an extra valve against water hammer when the pump stops.
Does borehole water need treatment?
The water analysis decides that, not the type of source. Iron and hardness are common, but choosing an iron filter or a softener without an analysis is guesswork. Their place in the node is after the mechanical filtration and before the heater and drinking points.