Hot Tub Control Room Position: Where to Put It and Why It Matters

Last updated: September 2026

When you’re planning a DIY hot tub, where you put the control room matters more than most people think. It decides how hard your pumps work, whether they’ll prime at all, how easy the tub is to maintain, and how noisy it is on a quiet evening. I’ve rebuilt my own control room since the first build, so I’ve learned some of this the hard way.

This post is about position and location. If you want the detail on sizing and laying out what goes inside, read it alongside Hot tub control room design considerations.

Where can the control room go? The options

Most DIY builds end up with one of these four layouts:

Position	Pros	Cons
Right next to the tub, sunk below the water line (under a deck, step or bench)	Shortest pipe runs, pumps stay primed, standard hot tub pumps, easy to hide	Needs drainage, and access can be cramped if you skimp on size
A sunken pit or vault a short distance away	Keeps noise and kit away from the seating area. Still below the water line	Longer pipes, more digging, and it still needs drainage
In a shed, garage or garden room at the same level	Dry, easy access, room to work	Often too far away, and often not low enough. Check the water line
Above the water line (e.g. uphill from the tub, or an above-ground tub with a raised plant room)	Sometimes the only option on a sloping site	Needs self-priming pumps or a priming circuit, with less flow and more cost

My own control room is below ground, right next to the tub. It’s the layout I’d recommend for most people. The mistake I made was making it too small. I’ve since widened it and rebuilt the plumbing, which I wrote about in My hot tub control room remodel.

Distance from the hot tub

In a perfect world, I always advise keeping the control room as close to the tub as possible. I know that sometimes it just isn’t possible, or it doesn’t look right. Either way, you’ll have a run of pipe to the tub and back, and that run has a cost.

What “head” actually means

Head is the resistance the pump has to push against, measured in feet (or metres) of water. The more head, the less flow comes out of the jets for the same pump.

In a hot tub, most of that head is friction. Every length of pipe, every bend, tee, valve, filter and heater adds some. Add it all up and you get the total dynamic head (TDH). Put a pump on a system with more TDH than it’s designed for, and the flow drops. The jets feel weak however big the pump’s label says it is.

What about height? You might expect any rise in height to add to the head. In a hot tub, the water goes out and comes back into the same tub, so the uphill and downhill parts of the loop largely cancel each other out. Where height really matters is priming, which I’ll come to below. For head, it’s the length of the run, the number of fittings and the pipe size that count. The one thing to watch is a loop that rises above the water line on its way, because air collects at the high point.

How to beat friction loss

There are four things you can do at the design stage:

1. Use a bigger pump. More power, more flow, so it can cope with a longer run. Simple, but it costs more to buy and run. How to correctly size a hot tub pump shows you how to work it out.
2. Add pumps. Run two pumps in parallel, on separate sets of jets or side by side, to get more flow. Pumps in series add pressure rather than flow, so parallel is usually what you want for jets. See How many pumps do you need?
3. Separate the jets from the circulation. The filter and heater add a lot of head. Put them on a small, dedicated circulation pump and let the jet pumps run straight to the jets and back. How to add a circulation pump explains how.
4. Upsize the pipe on long runs. Bigger pipe means much less friction. This is usually the cheapest fix of the lot.

How much difference does pipe size make?

Here are some realistic figures from my own pump sizing guide. They show the total dynamic head over 100ft of pipe at 100 GPM, which is roughly a 10-jet tub at 10 GPM per jet:

Pipe size	Head over 100ft (30m) at 100 GPM
1.5in	about 76ft
2in	about 27ft
2.5in	about 14ft
3in	about 8ft

That’s a huge difference just from changing the pipe diameter. If your control room is 30ft (10m) from the tub, you’ve got at least 60ft of pipe there and back before you count any fittings. On a run like that, going up a size or two on the long legs makes a real difference.

My mini conclusion: get the flow calculations right before you start. It’s much harder to fix once the pipes are buried and the concrete’s poured. For more on the plumbing side, see How does hot tub plumbing work?

Above or below the water line?

Ideally, below

Look at any plastic shell hot tub and you’ll find the pumps in the base. I’m stating the obvious here, but there’s a good reason for it.

Hot tub pumps are centrifugal pumps. They’re designed to force water out through the jets at high pressure, but they’re really bad at sucking air. A hot tub jet pump only works if it’s already full of water. So you need to feed water into the pump, and the easy way to do that is gravity.

Water finds its own level. Ignoring airlocks, the water in the whole system sits at the same height as the water in the tub. So if the pump is below the water line, gravity fills it, and it never has to suck water from the tub. That’s what you want with a standard hot tub pump.

You’ll hear the term “priming the pump”. That just means getting the air out so the pump and pipes are completely full of water. Because hot tub pumps are so bad at moving air, they won’t prime if they’re above the water line. Water won’t flow uphill into the pump, the pump can’t pull it up, and the system fails, however big the pump is.

The rule is simple: if you’re using a standard hot tub jet pump or circulation pump, it must sit below the water line of the tub.

The quick test

Not sure? Ask yourself this. If I filled the tub with water and there was no pump connected, would water flow into the control room on its own? If the answer’s no, you need to change the layout. Hot tub control room design considerations describes a simple test with temporary pipe before you commit. If you’re getting airlocks after filling, see How to deal with a hot tub air lock.

If it has to be above the water line

If there’s no way to get the pumps below the water line, don’t worry. There are solutions. You just need a different approach.

• Self-priming pumps. These are normally used on in-ground swimming pools, and they’re designed to suck (in a good way). They can draw water up into themselves without relying on gravity. The downside is lower flow. They’re built to move a lot of water slowly, not to drive jets. Unlike hot tub pumps, where a 3HP from one maker performs much like a 3HP from another, pool pumps vary enormously, so check the flow curve. You’ll also pay what I call the “swimming pool tax”. Anything with “pool” on it costs more, sometimes up to twice as much for the same output. Big single-speed self-priming pumps are also getting harder to find as manufacturers move to variable speed. My post What are the self-priming hot tub pump options? covers your choices, including splitting the jets across two smaller pumps.
• A priming circuit. A small self-priming pump and a few valves prime a standard centrifugal jet pump that sits above the water. It works, but it’s more complicated, and I see it as a last resort. I’ve shown how in Using a priming circuit above ground on a centrifugal hot tub pump.

Other things that decide the position

Distance and height are the big two. But I’ve seen plenty of builds where the control room works hydraulically and is still in the wrong place for another reason.

Drainage and flooding

A control room below the water line is, by definition, a hole in the ground below your tub. Sooner or later it’ll get water in it: a weeping union, rain through the lid, or you draining the tub. Give it a gravel base or a floor drain to a soakaway, or a sump with a small submersible pump. Keep the spa pack and electrics up off the floor. In my own remodel, I moved the blower onto a shelf with the air lines running up above the water line, and I fitted an IP55 box for the electrics. If your ground is heavy clay or you have a high water table, plan for a sump from day one.

Access for maintenance

You’ll be in there more than you think: changing filters, bleeding air, and one day swapping a pump or heater. Make sure you can:

• open the lid or hatch fully and climb in or reach everything,
• lift a filter cartridge straight out (a tall filter needs headroom above it; mine didn’t have enough first time round),
• reach every union and valve, and get a pump out without cutting pipe.

Don’t bury it under a deck you can’t lift or a patio you’ll never move. The size of the space itself is covered in the design considerations post, and Ultimate guide to hot tub pump wet ends shows why good access to the pump helps when it’s time for repairs.

Electrics and distance from the water

The control room is where the supply ends, so its position sets your cable route and where the isolator or disconnect goes. In the UK, the local isolator is typically at least 2m from the water and within sight of the tub. In the USA, the NEC wants the maintenance disconnect at least 5ft (1.5m) from the inside wall of the tub and within sight of it. A control room tucked right against the tub can still work. Just put the isolator where these rules are met, not on the control room lid. There’s more in Hot tub wiring explained, and the supply itself must be installed by a qualified electrician.

Noise

Pumps hum, blowers roar and heat pumps whirr. A control room under the seating area or next to a neighbour’s fence can be annoying at 10pm. A solid lid, a bit of acoustic lining and anti-vibration mounts all help, and so does not putting it under someone’s bedroom window. See Noisy hot tub pump? for fixes.

Ventilation and the heat pump

Pumps and spa packs give off heat, and a sealed underground box gets damp. A little ventilation keeps the electrics happier. If you’re heating with an air source heat pump, it needs open air around it, so it goes outside the control room. Put it close by, though, to keep the pipe runs short. 5 considerations before you install an air source heat pump covers placement.

Heat loss and frost

Long pipe runs lose heat, and in cold climates (much of the USA and Canada especially) exposed pipes can freeze. Another reason to keep the control room close. Insulate any pipe that isn’t buried or inside the insulated structure.

Common mistakes

• Putting the control room in the shed at the bottom of the garden, then wondering why the jets are weak.
• Putting a standard hot tub pump above the water line.
• Using the same small pipe on a long run as you would on a short one.
• No drainage in a sunken control room.
• Building it too small to change a filter or replace a pump (my mistake).
• Forgetting the cable route and isolator position until the patio’s down.
• Running pipes up over obstacles above the water line and creating air traps.

Planning your own build?

Planning, planning and more planning. That’s what makes a control room work. The Ultimate Hot Tub Control Room Guide takes you through laying out the pumps, filter, heater and spa pack (there’s also a stock tank version). My DIY hot tub plans include the plumbing layout and parts list for the standard sizes.

If your site is awkward, such as a sloping garden, a long run or a control room that has to go above the water line, I can work out the pipe sizes and pumps for you as part of a custom plumbing design or full architectural CAD and 3D plumbing design.

FAQs

How far can a hot tub control room be from the tub?

As close as possible. I’d aim for within about 15–20ft (4.5–6m). Further away can work, but you’ll need bigger pipes, and possibly bigger or more pumps, to keep the jets strong.

Does the hot tub pump have to be below the water line?

A standard hot tub (centrifugal) pump does, because it can’t suck water uphill to prime itself. If it must sit above the water line, use a self-priming pump or a priming circuit.

Can I put my hot tub equipment in a shed?

Yes, if the shed is close enough and the pumps sit below the tub’s water line. Many sheds are too far away or too high, so check both before you commit.

Does a below-ground control room need drainage?

Yes. Leaks, rain and draining the tub will all put water in it. Give it a gravel base or drain to a soakaway, or a sump pump, and keep the electrics raised.

Why are my jets weak when the control room is far away?

Long pipe runs and lots of fittings add friction (head), which cuts the pump’s flow. Bigger pipe on the long legs, separating circulation from the jets, or adding a second pump in parallel all help.

Got a question about where to put your control room? Drop it in the comments below. I read them all.

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