What I’d Change If I Built My DIY Hot Tub Again

Last updated: September 2026

Around eight years ago, I built my own DIY hot tub. You’ve probably seen it in the background of half my videos.

Fast forward to today and I’ve helped over 1,500 people build their own, and thousands more with spare parts for fixing their existing tubs. So I like to think I know a thing or two about what works, and what doesn’t.

With that in mind, I thought it’d be worth putting together an honest post about what I’d actually do differently if I started from scratch. Because believe me, I made plenty of mistakes first time round.

I’d use ICF instead of cinder block

My hot tub is built from cinder block. It’s a perfectly usable material (softer than a standard CMU block and widely available), but if I was doing it again, I’d go with ICF (insulated concrete form) without hesitation.

If you’ve spent any time on this blog or my YouTube channel, you’ll know I talk about ICF a lot. I always describe it as Lego for adults, and that’s genuinely the best way to put it. It’s lightweight, incredibly easy to cut (it’s just polystyrene), and simple to work with when it comes to routing your plumbing through it.

The big win though is what happens once it’s filled with concrete. You end up with something that’s both seriously strong and properly insulated. For a hot tub, that insulation matters a lot. It’s the obvious choice and I wish I’d used it from day one. If you’re weighing it up, read my guide to the best ICF blocks for building a hot tub, or see how it compares in my cinder block hot tub guide.

I’d start with a dual pump system

This is actually something I’ve already corrected on my own tub during a remodel a couple of years back when I added an air source heat pump. But I had to make it work with a single pump setup, which wasn’t exactly straightforward.

With a single pump system, you’ve got one pump doing everything: low speed for heating and filtration, high speed for your jets. A dual pump setup gives you a dedicated pump for each job, and the flexibility that comes with that is well worth the extra cost upfront. If you ever want to upgrade or add equipment down the line, you’ll be really glad you planned for it. My guide on how many pumps you need explains the options.

I’d make the control room bigger

This one I talk about constantly, and for good reason, because I got it badly wrong myself.

I measured up all the kit, then squeezed it into the smallest space I could get away with. Don’t do this. I’ve since had to go back and resize my own control room, so I’m speaking from painful experience (see my control room remodel).

Make it as big as the space allows. Bigger than you think you need. Trust me, when you’re trying to get in there to service or swap out a component, you will thank yourself for every centimetre of extra room. Have a look at hot tub control room design considerations before you fix the size.

I’d use mosaic pool tiles instead of large tiles

The last change I’d make is to the finish. I went with large tiles because I thought they’d be quicker and easier to lay. And they were, to a degree. But over the years, I’ve seen so many customer builds finished with beautiful mosaic pool tiles, and honestly? That look is in a different league.

Yes, they cost more. Yes, they take longer. Yes, they can be fiddly. But the end result is genuinely stunning, and I think it’s worth every extra penny and hour of effort. If I did it again, I’d skip the local hardware store tiles and invest properly in the finish. More on choosing them in hot tub tiles.

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So there you have it: four things I’d do differently. ICF over cinder block, dual pump from the start, a generously sized control room, and mosaic pool tiles for the finish. If you’re in the planning stages of your own build, hopefully this saves you from making the same mistakes I did. For more pitfalls, read Avoid these 7 DIY hot tub mistakes.

Planning your own build?

Getting the design right on paper is the cheapest way to avoid my mistakes. My hot tub plans give you dimensions, plumbing and a parts list, and if your space is unusual I can produce architectural CAD and a 3D plumbing design for you.

FAQs

Is ICF better than cinder block for a hot tub?

In my opinion, yes. ICF is lighter, easier to cut and plumb through, and once filled with concrete it’s both strong and insulated. Cinder block works, and mine is still going, but I’d choose ICF if I started again.

Do I need two pumps for a DIY hot tub?

You don’t strictly need them, but a dual pump setup gives you a dedicated pump for heating and filtration and another for the jets. It makes adding equipment like a heat pump much easier later.

How big should a hot tub control room be?

As big as the space allows, and bigger than you think you need. You’ll want room to reach every valve, pump and component for servicing.

Are mosaic tiles worth the extra cost?

I think so. They take longer and cost more, but they conform to curves and give a much better finish than large tiles.

Got questions about your project? Drop them in the comments or get in touch via the site. I’d love to help.

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