Hiring a Contractor to Build Your Hot Tub: How to Avoid Costly Mistakes

Last updated: September 2026

Getting a general contractor (or a local builder) to build your hot tub makes a lot of sense for many people. We don’t all have the time or the skills to do it ourselves. Most of the contractor-built tubs I’ve been involved with are superb: great quality, and they work well. But sometimes things go wrong, and when they do, it’s usually for the same few reasons. This guide is about avoiding them.

Why I wrote this: a real customer’s story

This post came about because a customer (who will remain nameless) had a total shocker with the general contractor (GC) who built their hot tub.

When I got the first pictures back, it looked absolutely beautiful. A really good job, I thought. They’d totally nailed it! But when the client went to fill it and switch it on, it was a different story. First, the control room flooded. That can happen to anyone (even those of us who help others build hot tubs), so I wasn’t too concerned at that point. I gave the client some advice on drying out the kit properly and then looking for the leak, which he found.

Then came the bigger problems. The plumbing wasn’t right. The GC hadn’t followed the plumbing diagrams I’d provided and had made a fundamental error: they’d mixed up the inward (suction) and outward (return) plumbing. There was also a random non-return valve on the skimmer line. Yes, the skimmer, not the blower line where it should have been.

When the client removed the non-return valve, water flowed in through the skimmer! Not the jets, the skimmer. The GC had connected the outward and inward water together, and because water takes the easiest route, it ignored the jets and just flowed back through the skimmer.

It wasn’t a total disaster, and it could be fixed. I worked with the client on what needed changing. But the client had already paid the GC in full before the kit had even been turned on, and the GC wasn’t returning his calls. With a few simple checks, most of this could have been avoided. Here’s how.

The clue is in the name

A “general contractor” is, by definition, not a specialist hot tub builder. Quite the opposite. GCs have a broad skill set that covers most jobs on your property. They’re good at a bit of everything, which is why they’re called general contractors and not plasterers or bricklayers.

They’re skilled tradespeople. In my experience they’re also incredibly helpful, and they never like to say no to a job. But the chances of your GC having built a hot tub before are slim. To date, I haven’t dealt with one who had. That’s not a problem. Just don’t assume they know everything.

Who should build it?

Option	Pros	Watch out for
General contractor or builder	Cheaper than a pool specialist. Great at groundwork, concrete and blockwork.	Little or no hot tub plumbing experience. Needs plans and checking.
Pool or spa specialist	Knows the plumbing, waterproofing and kit	Usually costs more. Some only fit their own designs.
Split it: builder for the structure, you (or a specialist) for the plumbing	Plays to everyone’s strengths	You coordinate the trades, and the interfaces need to be clear

Whatever you choose, the electrics are always a job for a qualified electrician. In the UK, a new hot tub circuit is notifiable under Part P and needs a registered electrician who can certify it. In the USA, it usually needs a permit and inspection under NEC Article 680. See Hot tub wiring explained.

Inform yourself

Just because you don’t have the skills to build the hot tub yourself doesn’t mean you can’t read up and understand the process. The last thing you want is to assume your GC knows everything and be totally hands off.

There’s no hardship in learning how the system works: the principles behind it, what goes on the suction side and the return side, and why parts like non-return valves go where they do. Arm yourself with that knowledge and you can check up on your GC. (Do it after they’ve gone for the day. Believe me, they won’t want you looking over their shoulder all day!) My guides on how hot tub plumbing works and planning the jets, pipes, drains and skimmer are a good place to start.

The structure is rarely the problem

GCs build things for a living. Laying a concrete base and four or five courses of block won’t trouble most of them, and they’ll do a great job. Where you need to take a real interest is the plumbing. It’s a little different from house plumbing, and that’s where things go wrong.

A few things that often catch builders out:

• Suction and return mixed up, as in the story above. The skimmer and main drains feed the pump’s suction. The jets are on the return.
• Check valves in the wrong place. The check valve goes on the blower’s air line (with the line looped above the water line), not on the skimmer. See my top tip for installing an air blower.
• Pumps above the water line. Standard hot tub pumps won’t prime. See where to put the control room.
• Poorly made joints. Every one should be primed and solvent welded, not forced into place. See the perfect PVC solvent weld joint.
• No hydrostatic relief valve in the floor of an in-ground tub. See why you need one.
• Waterproofing skipped or done to the wrong spec. See my waterproofing, grout and tile adhesive guide.

Make sure you have the right parts

In general, your GC won’t have trade accounts with pool and hot tub suppliers. You usually have to be registered in the trade to get one. So don’t rely on your GC to source the kit. If you’re not buying from me, get it from a reputable pool and hot tub supplier. It’s well worth sourcing the products yourself, so you know you’ve got the right kit, even if you aren’t putting it together. In the UK that’s parts4tubs.co.uk, and in the USA parts4tubs.com.

Get it in writing

A handshake and a verbal price aren’t enough for a job like this. Before any work starts, get a written quote and a written contract. It doesn’t need legal language. It just needs to set out what’s been agreed.

• The scope, with your plans attached and a line saying the work will be built to them.
• Who supplies what: materials, the hot tub kit, skips and so on.
• Start and finish dates, and what happens if they slip.
• The price and the payment schedule (see below). Make sure it’s a quote, not an estimate. Citizens Advice explains that “a quote is a promise from the trader to do the work at an agreed price”. An estimate is only a rough guess.
• Who gets the permits and the electrical certification.
• Clean-up, the use of subcontractors, and how changes (“variations”) will be priced.
• What “finished” means: filled, heated, running, and no leaks.

Structure your payments

I’d always agree a clear stage payment plan and pay against milestones. I’d certainly never pay for it all up front. Citizens Advice suggests avoiding large up-front payments, keeping any deposit to 25% or less, and paying in stages as the work progresses. Here’s how I’d tie the stages to a hot tub build:

Milestone	Check before you pay
Deposit (small)	Signed contract, plans agreed, start date booked
Dig, base and slab	Depth and size match the plans. Main drain, hydrostatic relief valve and sleeves in before the pour.
Walls and plumbing rough-in	Jets, skimmer and drains at the right heights. Suction and return traced against the plans. Pressure test the pipework before it’s buried.
Waterproofing	The specified membrane, two coats, and a flood test passed before tiling
Tiling, coping and control room	Pool-grade adhesive and grout. Kit fitted, joints properly made, pipes supported.
Final payment	Filled, heated and run for about a week with no leaks. Electrical certificate or inspection passed. Lien waivers collected (USA).

The most important stage is the sign-off. GCs are busy people with lots of projects, and once you sign off your tub, they won’t be back any time soon. I’d want to run the tub for a week and actually use it before signing off and making the final payment. Check for leaks and anything that isn’t right first.

Have the GC fill it and run all the kit so they can see the tub working for themselves. Their job is only done when there are no leaks, the water is heating up, and the blower and jets work perfectly. My guide on how to fill a hot tub the correct way is a good checklist for that first fill.

Inspect the build and check it against the plans

I can’t stress this one enough. Every evening, or at least every couple of days, look at the build yourself and check it against the plans. Trace the plumbing to make sure the right parts are connected, and understand what’s been put where and why it’s there.

In the case above, the client wasn’t around to inspect anything during the build. He left it all to the GC. If you can’t be there, arrange for someone who knows what they’re looking at to check it for you, especially before anything is concreted in or buried. Take photos of all the plumbing before it disappears. They’re invaluable later if you ever need to track down a leak.

In the UK: TrustMark, contracts and your rights

• Finding someone. TrustMark is the government-endorsed quality scheme for work in and around the home. Its registered businesses are vetted, and it has a complaints process. Check that they’re registered for the specific trade you need. Citizens Advice also suggests getting at least three written quotes, asking for recent references you can contact, and being wary of anyone with only a mobile number.
• Insurance. Check they have public liability insurance (and employers’ liability if they have staff), and check your own home insurance too.
• Your legal rights. Under section 49 of the Consumer Rights Act 2015, every service contract includes a term that the trader must perform the service “with reasonable care and skill”. If they don’t, Citizens Advice explains you can ask them to put it right within a reasonable time, or in some cases get money back. Put your complaint in writing, with photos.
• Cooling-off period. If you agreed the job away from the trader’s premises (at your home, by phone or online), you usually have 14 days to cancel. The clock starts the day after you give the go-ahead. If you ask them to start within that period, you’ll have to pay for the work done.
• Permissions. You, the homeowner, are responsible for planning and Building Regulations. A garden hot tub rarely needs planning permission, but the electrics must meet Part P. See Do I need a permit for my hot tub?

In the USA: licenses, permits and lien waivers

• Check the license. Most states license contractors, and the rules vary by state. Look them up on your state board’s website before you sign. For example, California’s CSLB has a license check that shows status and complaint disclosures. Washington’s L&I advises that you verify the license, make sure they’re bonded and insured, get at least three written bids and a written contract, and consider a performance bond on larger jobs.
• Permits. Many cities and counties need a permit for an in-ground spa, plus electrical permits and inspections under NEC Article 680. Make it clear in the contract who pulls the permits. An unpermitted tub can cause problems when you sell or insure the house.
• Mechanic’s liens and lien waivers. This one catches people out. Subcontractors and suppliers can have lien rights over your property even though they were hired by your GC, not you. So if your GC doesn’t pay them, you could face a lien even though you’ve paid in full. Protect yourself by collecting lien waivers or releases from the GC, and from the main subs and suppliers, as you make each payment, and a final waiver before the last payment. Lien law is state-specific, so check your state’s forms and rules.

I can help

This is one of the areas where I can really help, both you and your GC:

• Plans. My DIY hot tub plans include CAD drawings, full plumbing diagrams, a parts list, the build guide and videos, plus lifetime email support. They tell your GC exactly what to build, and they give you enough understanding to check it and ask intelligent questions.
• Custom designs. For something bespoke, design it in Tub & Pool Designer Pro, and I’ll turn it into architectural CAD and a 3D plumbing design your contractor can build from and you can use for permits. Here’s how the custom design process works.
• Plumbing consultancy. If you want me involved in the plumbing side of the build itself, there’s a hot tub plumbing consultancy option.
• Parts. The right kit from parts4tubs.co.uk or parts4tubs.com, so you start with everything you need.

The builds that turn out best are the ones where the GC isn’t afraid to ask a question before they glue a joint. There’s nothing wrong with asking for help.

For more on what goes wrong on builds generally, see Avoid these 7 DIY hot tub mistakes.

FAQs

Can a general contractor build an in-ground hot tub?

Yes. Most GCs will do a great job of the structure. Give them detailed plans, supply the right parts, and check the plumbing yourself, because that’s where inexperienced builders go wrong.

How should I pay a contractor for a hot tub build?

In stages against milestones, with a small deposit (Citizens Advice suggests 25% or less) and the final payment only after the tub has been filled, heated and run without leaks.

What should a hot tub building contract include?

The scope with the plans attached, who supplies what, dates, the fixed price and payment schedule, who handles permits and electrics, how changes are priced, and a clear definition of “finished”.

What is a lien waiver and do I need one?

In the USA, a lien waiver is a signed document in which a contractor, subcontractor or supplier gives up its right to put a lien on your property for the work paid for. Collect them with each payment so an unpaid sub can’t come after your home.

What are my rights if a builder does a bad job in the UK?

The Consumer Rights Act 2015 requires services to be carried out with reasonable care and skill. If they aren’t, you can ask the trader to put it right, or in some cases get a price reduction or refund. Citizens Advice can help with next steps.

Using a contractor for your build, or had a good (or bad) experience? Tell me in the comments below. I read them all.

Cheers,
Andi

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Thanks - Andi

 

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