hemp on an unvented cylinder

found block of newish flats where the immersion and expansion vessel have been joined using hemp .
I know its not potable water, but is hemp aceptable or should all 50 flats be rejoined ? ( costing £1,000's)

hemp is not acceptable for any domestic water services as it harbours microbiological growth

know its not potable water,

Click to expand...

wot is your question kevplumb ?

err dunno but you cant use hemp on potable water

it aint so ipso facto you can

if that was a question

just seems odd that u r allowed to use a material that allows micobiological growth.
the cylinder supplies a shower which could distribute Leigonella if it grew in the cylinder

now ang on i never said it was allowed

i said you can

can anyone PLEASE give a clear answer.

Why are you so interested in this.

Water Supply (Water Fittings) Regulations 1999


The actual text from the regulations:

Schedule 2: Paragraph 2: Materials and substances in contact with water

2. (1) Subject to sub-paragraph (2) below, no material or substance, either alone or in combination with any other material or substance or with

the contents of any water fitting of which it forms a part, which causes or is likely to cause contamination of water shall be used in the construction, installation, renewal, repair or replacement of any water fitting which conveys or receives, or may convey or receive, water supplied for domestic or food production purposes.

(2) This requirement does not apply to a water fitting downstream of a terminal fitting supplying wholesome water where-

a. the use to which the water downstream is put does not require wholesome water; and
b. a suitable arrangement or device to prevent backflow is installed.




The legal guidance part:

G2.15 Jointing compounds used for sealing screwed water fittings should comply with BS 6956: Part 5.



And the water industry recomendation:

R2.15 Only jointing compounds that comply with G2.15 are to be used for jointing screwed pipes and fittings. Other proprietry compounds and hemp are not acceptable as they may promote microbial growth.


Potable water (correctly known as "wholesome water") is drinking water supplied via the service pipework. It could be argued that hot water from a cylinder is not normally drunk however, the AFAIK although hot water falls into category 2 it is still regarded as wholesome regarding contamination from unsuitable materials.


Therfore HEMP is NOT permitted on wholesome ( ie HOT) water pipework/fittings.


There are suitable alternatives to hemp that comply with BS 6956 Pt5 eg Fernox Fibre tape.