An alternative Hot Tub

I’ve thus far been considering a Dutch Tub hot tub:

  • I think they look cool
  • Their water volume is “only” about 650 litres, so not too much to heat up and keep walm. Also not too much weight.

BUT their size does mean while they are super comfy for 2 people, as soon as you go over that, it gets a bit of a squeeze. (the bottom of the Dutch Tub tubs domes up).
Look at these 2 pic’s of 1 and 2 people in a Dutch Tub (there is only one size). Click on either pic and you’ll get the full size version where yu can see toes at the other side of the tub and arm spans etc.

dutchtub-2_people    dutchtub-1_person

I’ve just found Cashen Hot Tubs. Their tubs are 100% made from timber from local (Cornish) forests. Mostly from Dutchy controlled forests less than 6 miles from their sawmill.

They come with a wood burner heating option that looks the same as the hot tubs I was in at last years (2012) Nova Festival:

Wood fuelled hot tub at Nova Festival 2012


The 1.7m diameter Cashen hot tub is down as suitable for 4-5 people. It’s about 400 kg empty, so add the 1,800 litres of water, the burning fire and a few people and you rapidly get to 2,500 kg or a bit more.

  • The inside depth of the tub is 920mm, outside height is 1090mm. They have said they can make a shallower tub to make the most of your sea view. But will that mean cold shoulders ?
  • They can also add a filtration system to the wood fired hot tubs.

Below are some photos and other info from the  Cashen Hot Tub Website and some emails from them (so accurate early 2013):

Wood Burner Hot Tubs (Elec heated a bit more £)
1.5m (4.5ft) dia. 1,600 litres seats 3-4 people £3,125
1.7m (5ft) dia. 1,800 litres seats 4-5 people £3,475
1.9m (6ft) dia. 2,500 litres seats 5-6 people £3,725

The tubs have an “inside depth of the tub is 920 mm, outside height is 1090 mm. If you were interested in a shallower tub to make the most of your sea view, this could be accommodated.”

Prices include our eco-friendly underwater wood-burning heater and integral seating as standard.

The stove is made from marine grade aluminium. They can be replaced at £800.

Hot Tub Optional Extras
Wooden Steps (I assume external to get in and out !) £195
Lift off wooden cover £265
Lift off custom made insulated cover £350
Pipe work screening
– which it looks like the Nova Festival tubs had. The Cashen photos below show tubs without a cover over the pipe work.
Filtration system £515
Stainless steel finish for chimney £180

Water Temp & Stove Size

Reading elsewhere, hot tubs tend to run around 36° degrees. The stove needs to be sized to not over or under heat the size of the tub.

Hot Tub Placement & Maintenance

The more they are not left the better.

“Use it and wash it regularly, another important thing is to make sure the is adequate air circulation underneath the tub. There is no problems using sea water in the tub as the stove is a manufactured of marine aluminium, the actual barrel itself works better with salt water as it keeps the moisture better and it slows down the dry out process.”

Photos from the Cashen Hot Tub Website:









From another Website:

wood fired hot tub - schematic

Hot water heat recovery

What device(s) to put where to recapture as much of the heat from waste / grey water needs a decision.

The solutions from are clearly all very efficient and appear to be the same or similar to those that are well used in the US, where a lot of properties have their heating systems in the basement.

They are based on an “instant” transfer of the waste water heat to the mixer in the shower and also to the cold water feed to the water heating system.

BUT, the planned house will have clothes washing machines, a dishwasher and 2 showers on the ground floor. Being on the ground floor they wouldn’t work with all the recoupenergy solutions. Also a washing machine, dishwasher, bath (or hot tub) generates the waste water, some time after the hot water tank has been re-filled with mains cold water.

So in those circumstances, the Heat Squirrel (scroll to the bottom) could be better and could provide a single (so a lot cheaper) whole house solution for all waste / grey hot water heat recovery. They are about £399 (not installed). The heat squirrel has a 120 litre capacity.

A key consideration / idea will be:

Can the waste water input be regulated so that only waste water that is warmer than the water in the heat squirrel is let in to it?

It seems that for a shower, the recoupenergy solutions will be the most efficient, but for the whole house, and the total cost, a single heat squirrel could be better than a heat squirrel and one or more recoupenergy solutions.

Heat Squirrel Schematic

Heat Squirrel - schematic
Heat Squirrel - installed

New “Dutchtub Wood”

The DutchTub team have created a version of their “tea cup” hot tub that is encircled by wood, which might look better for Silver Spray.

I asked and “Indeed, the Dutchtub wood has the same inner shape as the Dutchtub Original.”

The original Dutch Tub can weigh 1400 kg / 3000 lbs when full of water and 4 people. They suggest a small platform under the tub can spread the total weight on more square meters than just the four legs of the tub. ”


  • Length: 170 cm/67 inch
  • Width: 234 cm/92 inch
  • Height: 82 cm/32 inch
  • Weight: 85 kg/187 Ibs
  • Capacity: 650 liter/171 gallon
  • Material: 
    • Glassfibre polyester (RAL 7003, single color option)
    • Stainless steel
    • Preserved wood
  • Additional: This design is developed in collaboration with Feather Down Farm Days®
  • Delivery: The Dutchtub Wood will be delivered with a fire basket for the spiral, a special wok, a fire shield, a turbo connection for fast heating and a fiberglass cover
  • Check out the accesories.