Ground Bonding a Hot Tub or Plunge Pool: What It Is and Do You Need It?

Last updated: September 2026

“Ground bonding” is one of those phrases that gets thrown around on forums as if everyone knows what it means. Most people don’t, and plenty of the advice out there mixes up three different things: earthing (grounding), RCD or GFCI protection, and equipotential bonding. On a DIY hot tub or plunge pool, you need to know the difference, because part of the bonding has to go in before you pour the concrete, long before the electrician turns up to wire the spa pack.

This post explains what bonding is, what the rules say in the USA (NEC 680.26) and the UK (BS 7671), and what you need to do as a DIYer. What it isn’t is a wiring guide. Bonding is electrical safety work, so the design, connections and testing belong to a qualified electrician, and in most places they need to be inspected or certified.

Grounding, RCDs and bonding: three different jobs

I used to lump grounding and bonding together as one thing, but they do different jobs, and getting that wrong leads to some bad DIY decisions (like hammering in a ground rod and thinking the job’s done).

What it is	What it does	UK name / USA name
Earthing / grounding	A protective conductor in the circuit connects the metal case of the spa pack, pump or heater back to the supply’s earth. If a live wire touches the case, the fault current flows and the protective device trips.	Circuit protective conductor (CPC) / equipment grounding conductor (EGC)
Residual current protection	Detects a small leakage current (30mA in the UK, around 5mA for a US GFCI) and cuts the power fast enough to protect a person.	RCD or RCBO / GFCI
Equipotential bonding	Connects all the metal in and around the water (rebar, metal fittings, pump motors, handrails) so it’s all at the same voltage. If a fault or stray voltage appears, there’s no difference between the things you can touch at once, so no current flows through you.	Supplementary (equipotential) bonding / equipotential bonding

A hot tub needs all three. Your RCD or GFCI is the one that saves your life in most faults, and the protective conductor lets it do its job. Bonding covers the situations those can’t: small voltages that won’t trip anything but are still dangerous when you’re wet, barefoot and sitting in conductive water. As the NEC puts it, equipotential bonding is there “to reduce voltage gradients in the pool area”.

USA: NEC 680.26 equipotential bonding

In the USA, pools, spas and hot tubs are covered by NEC Article 680. Bonding is in 680.26. Your city or county adopts a particular edition of the NEC, sometimes with local amendments, so check which one applies with your inspector. The quotes below are from the 2017 and 2023 editions.

Does it apply to a hot tub?

For an outdoor spa or hot tub, 680.42 says it must also comply with Part II of Article 680, which includes the 680.26 bonding rules. There’s an exception for perimeter bonding, but only for a spa that is listed as a self-contained spa for aboveground use, installed on or above grade, with its top rim at least 28in (710mm) above all perimeter surfaces within 30in (760mm). That describes a shop-bought acrylic hot tub on a pad.

A DIY concrete, block or ICF tub isn’t a listed self-contained spa, and an in-ground one obviously doesn’t have its rim 28in above the ground around it. So plan on the full 680.26 bonding for a DIY in-ground or built-in tub or plunge pool. Indoor spas fall under 680.43, which has its own bonding list covering fittings, circulation equipment and metal surfaces, raceways and piping within 5ft of the inside walls. Its perimeter exemption is only for a listed self-contained spa installed above an indoor finished floor, so a DIY tub sunk into a basement floor still needs a proper conversation with your inspector. Indoor builds are covered in Build a hot tub in your basement.

What gets bonded

Under 680.26(B), the equipotential bonding grid ties together:

1. The shell. For a concrete shell, that’s the unencapsulated (bare) rebar, “bonded together by steel tie wires or the equivalent”. If the shell isn’t reinforced in a way that works, a copper grid of 8 AWG bare solid copper on a 12in by 12in pattern is the alternative.
2. The perimeter surfaces, extending 3ft (0.9m) horizontally out from the inside walls. This can be done with the rebar or wire mesh in the deck, or with a single 8 AWG bare solid copper conductor run around the tub 18–24in from the inside wall and 4–6in below the subgrade, connected to the shell at four evenly spaced points.
3. Metal parts of the structure, such as metal wall panels.
4. Underwater lights: metal forming shells and brackets. See my hot tub lights guide.
5. Metal fittings in or attached to the shell.
6. Electrical equipment on the circulation system, such as pump motors and heaters. Most pumps and spa packs sold for this market have an external bonding lug for exactly this.
7. Fixed metal parts such as handrails, metal fences, pipes and conduit, generally within 5ft horizontally of the inside walls or 12ft above the water.

And the water itself. If none of the bonded parts touch the water, 680.26(C) requires a corrosion-resistant conductive surface of at least 9 square inches in contact with it. Water-bonding fittings are made for this.

What with, and what it connects to

The bonding conductor is solid copper no smaller than 8 AWG, bare or insulated, connected with fittings listed for the job (and for direct burial or concrete encasement where needed). Crucially, the NEC says “equipotential bonding is not required to extend to or be attached to any panelboard, service equipment, or grounding electrode”. It also says the pool structure and rebar aren’t permitted to be used as a grounding electrode. Bonding and grounding are separate systems.

Many inspectors want to see the rebar bonding before the concrete is poured, so find out when your inspections are before you order concrete. There’s more on US permits in Do I need a permit for my hot tub?

UK: supplementary bonding under BS 7671

In the UK, the rules are in BS 7671, the IET Wiring Regulations. Swimming pools are a special location under Section 702, which divides the area into zones: zone 0 is inside the basin, zone 1 extends 2m from the edge of the basin, and zone 2 a further 1.5m beyond that. Section 702 requires supplementary protective equipotential bonding: all extraneous-conductive-parts in zones 0, 1 and 2 are connected to the protective conductors of equipment with exposed-conductive-parts in those zones. Unlike a bathroom, there’s no exemption from supplementary bonding for a pool, and that includes the rebar in a concrete pool, with a connection brought out to an accessible point for testing.

Where hot tubs fit in

This is where people get confused, because BS 7671 doesn’t have a section for hot tubs. NAPIT says BS 7671 doesn’t have specific requirements for residential hot tubs, so the electrician applies the general requirements and their judgement. Section 701 (bathrooms) is the nearest parallel indoors, and Section 702 applies to commercial or permanent ground-built tubs, and can be used as a basis for a safe design where there’s any doubt.

The IET’s own guidance on hot tubs goes further for outdoor tubs. It says the risk is similar to a bathroom, “but with the additional risk of barefoot contact with Earth”, so the designer should apply Section 702 in full outdoors, and Section 701 indoors. It also discourages PME earthing for an outdoor hot tub and suggests a TT system as best practice. That’s a design decision for your electrician, not something to guess at.

So for a DIY in-ground or built-in hot tub or plunge pool in the UK, assume Section 702 applies. That means bonding the rebar and any metalwork, and getting the connection out of the concrete before you pour.

The rest of the UK picture

• Part P: a new hot tub circuit is notifiable work in England and Wales, so use a registered electrician who can certify it.
• RCD: 30mA, at least Type A, or whatever the spa pack maker specifies.
• Isolator: the IET says outside zone 1, 2m from the edge of the basin.
• Lights in the water: only 12V SELV. There’s more in my hot tub lights guide.

The full supply side is in A guide to hot tub electrics and Hot tub wiring explained.

UK and USA side by side

	UK	USA
Rules	BS 7671 Section 702 (pools). For hot tubs, IET guidance: 702 outdoors, 701 indoors	NEC 680.26, applied to outdoor spas by 680.42 (indoor: 680.43)
What’s bonded	Extraneous-conductive-parts in zones 0–2, including rebar, to the protective conductors of equipment	Rebar shell, 3ft perimeter, metal fittings, lights, pump motors and heaters, fixed metal nearby, and the water
Conductor	Copper, sized by the electrician (2.5mm² with mechanical protection, 4mm² without, as a minimum between extraneous parts)	Solid copper, no smaller than 8 AWG
Ground rod?	Not the point of supplementary bonding. A TT earth electrode may be part of the supply design, which is the electrician’s call	Not required. The grid doesn’t need to connect to a grounding electrode
Sign-off	Part P notification and an Electrical Installation Certificate	Permit and inspection in most areas, often including a pre-pour bonding inspection

What you need to do as a DIYer

You’re not wiring anything here. Your job is to make sure the electrician can do theirs, because once the concrete is in, the rebar is gone for good.

1. Get your electrician involved at the planning stage, not when the tub is finished. Ask them how they want the rebar, perimeter and metalwork bonded, and what they need from you before the pour.
2. Tie the rebar properly. In the USA, the NEC method relies on steel tie wires joining the bars. It’s good practice anyway, and there’s more in my rebar guide. Don’t use plastic-coated rebar or plastic clips without asking, because encapsulated steel doesn’t count.
3. Leave the bonding connection where they want it. Typically that’s a bonding conductor, connected to the rebar with a listed clamp (USA) or brought out to an accessible point (UK), running to where the control room and spa pack will be. Your control room position matters here.
4. Don’t forget the deck. In the USA, the 3ft perimeter has to be bonded too, so plan it alongside the tub’s slab and any patio or deck around it.
5. Photograph everything before the concrete goes in, and book the inspection if one’s required.
6. Choose metal parts with bonding in mind. Handrails, metal jet fittings, light niches and a steel stock tank all need bonding. Plastic fittings and SELV lights make life simpler. If you’re building a metal tank, see my stock tank guide.

Myths and bad advice

• “Just drive a ground rod next to the tub.” That’s grounding, not bonding, and a ground rod on its own doesn’t reduce the voltage differences around the water. In the USA the bonding grid doesn’t need one at all. Adding extra rods or earth electrodes isn’t something to do on your own. That’s part of the supply design.
• “Under 25 ohms and you’re fine.” That figure relates to single ground rod electrodes on a building’s grounding system, not to pool bonding. Bonding is tested for continuity by an electrician.
• “Bonding is for lightning and static.” Not in this context. Pool and spa bonding is about stopping shock from voltage gradients around the water.
• “My RCD or GFCI makes bonding pointless.” They do different jobs, and the rules require both.
• “I’ll sort the bonding later.” The rebar can’t be bonded once it’s inside the concrete.

Common mistakes on DIY builds

• Pouring the slab before the electrician or inspector has seen the rebar bonding.
• Only bonding the tub’s shell and forgetting the deck, handrail or a metal fence nearby.
• Using stranded or undersized wire, or ordinary hose clips, for bonding connections.
• Forgetting the pump motor bonding lug in the control room.
• Treating a DIY in-ground tub like a shop-bought portable hot tub when it comes to the rules.
• Ignoring nuisance tingles in the water. If you feel anything, switch off at the isolator, stay out and get an electrician. My guide to why a hot tub trips the breaker covers the other side of electrical faults.

Planning your own build?

Electrics and bonding are much easier when they’re planned from the start, alongside the plumbing and the slab. My DIY hot tub plans give you the dimensions, slab, plumbing layout and a full parts list, so you can sit down with your electrician with a proper drawing. For a plunge pool, start with How to build a DIY plunge pool. If you want a custom design you can take to an electrician, builder or permit office, I can draw it up as architectural CAD with a 3D plumbing design.

FAQs

What is the difference between grounding and bonding a hot tub?

Grounding (earthing) connects the metal cases of the equipment back to the supply earth so a fault trips the protective device. Bonding connects all the metal in and around the water together so it’s all at the same voltage. A hot tub needs both, plus RCD or GFCI protection.

Does a DIY hot tub need to be bonded?

In the USA, a DIY in-ground or built-in tub should be treated as needing full NEC 680.26 bonding, because it isn’t a listed self-contained spa. In the UK, BS 7671 Section 702 requires supplementary bonding for pools, and IET guidance applies it to outdoor hot tubs. Your electrician confirms the details.

Do I need a ground rod for a hot tub?

Not for bonding. In the USA, the equipotential bonding grid doesn’t have to connect to a ground rod, panel or service. In the UK, whether the supply uses an earth electrode (a TT system) is a design decision for your electrician.

What size wire is used for pool and hot tub bonding?

In the USA, solid copper no smaller than 8 AWG. In the UK, supplementary bonding conductors are sized under BS 7671, with a minimum of 2.5mm² copper if mechanically protected or 4mm² if not, between extraneous-conductive-parts. Your electrician sizes it for the installation.

Does the rebar in a hot tub slab need bonding?

For an in-ground or built-in DIY tub, yes, in both the UK and the USA, and it has to be done before the pour. For a pad under a shop-bought tub in the USA, some manufacturers say to attach the mesh to a bond wire, so ask your electrician. See my concrete slab guide.

Can I do the bonding myself?

You can prepare for it, by tying the rebar and leaving access where your electrician wants it. The design, connections and testing should be done by a qualified electrician, and in most places they’ll need to be certified or inspected.

Got a question about bonding on your build? Drop it in the comments below. I read them all, though for anything specific to your installation, your electrician has the final say.

Cheers,
Andi

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Hi, Andi here. I own Buildahottub.com and also write all of the articles and info pages on the site. Some years back now, I built my own hot tub but struggled to find the information I needed. So, once my tub was complete, I started this website to help others in their own pursuit of hot tub and plunge pools DIY building information.

Fast forward to 2025, I've helped over 1400+ DIY customers just like you all over the world build hot tubs and pools. Have a good look around the site, there are lots of resources here. Please do get in touch if I can help you. - Cheers, Andi