The Group's aim is to identify, survey, protect and promote geological and geomorphological sites in the former County of Avon - the modern unitary authorities of Bath and North East Somerset, Bristol, North Somerset and South Gloucestershire. RIGS are selected for their educational, research, historical and aesthetic value.

Monday 25 February 2013

The Hot Well, Bristol

The Hot Well spring, Bristol
From rags to riches and back again - 
the story of the Hotwells spa
The old Hotwell House on the banks of the Avon. Built in 1696, it held a pump rooms and lodgings for visitors. After the terminal decline of the Hot Wells spa, it was demolished in 1822 and no remnants of its former glories remain, the site being adjacent to The Portway.


The King’s Spring in Bath has been exploited by humans since 836BC, most famously by the Romans who built the first baths, and then later during the spa age of the 18th century. Less renowned is the eponymous spring of Hotwells in Bristol. At its peak in the Georgian era, the “Hot Well” served a fully functioning pump room and hot baths, and provided the catalyst for much of the development in Clifton. Today, the spring has diminished in flow and is only visible at low tide as a trickle emanating from the banks of the River Avon.

The modern-day resurgence of the Hot Well from the banks of the Avon as visible at low tide. All photo credits: Charly Stamper


The spring was first mentioned in 15th century historical records, and by the 1630s it was being regularly visited by society. The thermal water emerged on both sides of the Avon, roughly opposite the intersection the The Portway and Bridge Valley Road. It was contemporarily described as being "milky white" and was thought to have restorative properties, particularly for "hot livers, feeble brains and red pimply faces". During the 17th century the spring was relatively inaccessible, for there was no formal path and a descent from Clifton involved “200 slippery steps”.

As the popularity of spas increased in the Georgian era, so did the number of visitors to Lower Clifton. Initially, development focused on the area adjacent to the natural resurgence, with the building of a spa (old Hotwell House), entertainment complexes (Jacob Wells theatre) and genteel housing (eg. Dowry Square). In the 18th century the spring’s reputed curing powers extended to venereal disease, tuberculosis and cancer.

Strangers' Burial Ground, Lower Clifton Hill. By the 1750s, the Hot Well acquired a reputation for curing tuberculosis; however, these claims were unfounded and an overflow burial ground was instated to cater for unfortunate commoners who came from outside of the parish.

The main dent in the Hot Well's popularity remained the distance and difficulty of access down the steep sides of the Avon Gorge, and in the mid 1780s Thomas Morgan embarked on an ambitious engineering project to bring the waters to the heart of Clifton. From Sion Row he drilled a shaft some 250ft through the Carboniferous limestone to tap the hot waters, supplying water to a new pump room with hot baths and a reading room, later to become the St Vincent Rocks Hotel (now Avon Gorge Hotel). By 1793, this diversion had become known as the “New Hot Well”.

In the following years, both springs began to cool, almost certainly as result of increased groundwater mixing. This coincided with a nationwide decline in spa popularity in favour of sea bathing, increase in subscription charges and end of the Napoleonic Wars, meaning British people were free to travel abroad. Several revival attempts in the 19th century failed to capture former glories, and the spring is no longer commercially exploited. 

The Colonnade, Hotwells Road. Originally a shopping arcade, it was built in 1786 as an attempt at reviving the failing fortunes of the Hot Wells spa.

Modern day studies of the hot springs of the Avon area have tried to shed some light on the source and science behind their existence. In 1993, the yield of the Hot Well was measured at 0.41 x 10^6 litres a day, about a third of the present-day flow recorded at the King’s Spring in Bath and enough to fill an Olympic-sized swimming pool in a week. Compositionally, the two springs are very similar, being rich in calcium and sulphates, though 25% of the Hot Well volume is cold groundwater, reflected in the relatively low average temperature of 24ºC.

The source of the two springs is thought to be rainfall in the Mendip Hills, some 15km to the south-west.  Measured carbon isotopes (∂13C) are consistent with storage in Carboniferous Limestone, and hydrogen and oxygen isotopes provide evidence that most of the water is meteoric in origin. The head at this elevated topography is high enough to force the water down beneath the Coal Measures to a depth of around 2.7km in the Bristol-Bath basin and heat the groundwater; silica geothermometers indicate the thermal component of the springs reaches a maximum temperature of 72ºC. 

Cross section showing flow of groundwater through Carboniferous Limestone from source in the Mendip Hills to resurgence in Bath and Hotwells (Andrews et al., 1982).
The overlying stratum of the Coal Measures is a proven aquiclude, so no upward migration can take place. The area north of the Mendips is heavily faulted and folded from both Mesozoic and Tertiary tectonics, so the water migration is unlikely to be direct. Tritium (3H) was produced by thermonuclear weapons testing in the 1950s and is used to identify any modern-day recharge in groundwater. Low tritium levels in the Hot Wells indicate only minor amount of mixing with of ‘recent’ waters, and the majority is likely to be up to 10,000 years old. At the end of its journey, the Hot Well resurges directly from Carboniferous Limestone into the channel of the Avon river.


Although the Hot Well spring has had its heyday, the King’s Spring at Bath remains at the heart of the city’s tourist trade. In 2011, two companies (Eden Energy and UK Methane Ltd) were given licenses by Mendip district council to begin a feasibility study for the controversial practice known as “fracking”. Concerns were immediately raised by councilors in Bath and led to a subsequent uproar in the local (and further afield) media. A specially commissioned British Geological Survey report concluded that the risk to the Bath springs was no higher than any other part of the UK, although critics point out that relatively little is still known about the subterranean flow of the groundwater. The energy companies are a long way off obtaining the planning permission needed to begin exploratory drilling, but the authorities would to well to bear in mind the role that human intervention had in the decline of the Hot Well spring.

Charly Stamper


Andrews JN, Burgess WG, Edmunds WM, Kay RLF & Lee DJ (1982) The thermal springs of Bath. Nature 298: 339-343.

Atkinson TC & Davison RM (2002) Is the water still hot? Sustainability and the thermal springs at Bath, England. Geological Society, London, Special Publications, 193: 15-40.

Clifton and Hotwells Conservation Area Character Appraisal (2010) Bristol City Council http://www.bristol.gov.uk/sites/default/files/assets/documents/clifton-and-hotwells-character-appraisal.pdf

Gallois RW (2007) The formation of the hot springs at Bath Spa, U.K. Geol. Mag. Vol. 144, 741-747

Jones, D (1992) History of Clifton. Phillimore.

Kellaway, GA (1993) The hot springs of Bristol and Bath. Proceedings of the Ussher Society, 8, 83-88.

Mowl, T (1991) To Build the Second City: Architects and Craftsmen of Georgian Bristol. Redcliffe Press Ltd.

Smith NJP & Darling WG (2012) Potential problems within the Bath and North East Somerset Council and surrounding area with respect to hydrocarbon and other exploration and production. British Geological Survey Commissioned Report CR/12/055, 26 pp.


  1. Very interesting. I have a particular interest in spas and my undergraduate dissertation incorporated some minor ones found in Shropshire.

  2. Richard Ashley 13 February 2013
    Some years ago when working for Kingswood BC I heared stories of a warm spring emptying into the Warmley Brook. There is a road called Hot Water Lane off Station Road. My investigations in the area faild to fid a warm spring but the course of the Warmley Brook had been realigned and it is possible that the spring could have been diverted. Does any one else have any information on this?