Marine Group

  • Cardiff 02920 343459
  • Aberystwyth 01970 611422
  • Port Dinorwic 01248 671500/01248 670176
  • Burry Port 01554 835 691
  • Watchet 01984 322230

Osmosis Treatment Centre

We are a leading Hot Vac Osmosis Treatment Centre

Osmosis Treatment Centre

We are a leading Hot Vac Osmosis Treatment Centre

We recommend the Hot Vac system as the most successful treatment for Osmosis.

This system provides a complete osmosis treatment package. We have over 25 years experience in treating osmosis.



Osmosis is the physical process by which a liquid from a weaker medium is drawn through a semi-permeable membrane into a stronger liquid medium. For boats this causes degeneration within the glass fibre laminate as a chemical reaction occurs between water and un-reacted substances remaining in the manufactured hull. When water enters the hull through the gelcoat it reacts with the chemical components creating acidic substances, this creates pressure behind the gelcoat causing blisters and eventually cracking. Once the gelcoat is breached in this manner, the underlying laminate absorbs water like a sponge. Osmosis depends on many factors including: the type of water in which the hull is moored, the temperature of the water and most importantly the quality of the original hull construction.


To protect against osmosis it is necessary to seal the surface of the hull over the existing gelcoat. The best time to apply an anti-osmosis system is before the boat has been launched. However, protective systems cannot stop osmosis once it has started, or prevent it from occurring in poorly constructed hulls. If your vessel is dry you can use Gelshield 200 as a preventive measure to help reduce the risk of osmosis. To find out more please visit yachtpaint.


  • We strip off the old gelcoat using a gel plane system
  • The hull is then steam cleaned to remove surface osmotic impurities
  • The hull is then dried using our Hot Vac machine to lower the moisture content to an acceptable level. The Hot Vac machine also gives your hull a post-cure thus strengthening the laminate.
  • The hull is then filled and coated with International Paint Gelshield System
  • Finally the hull is antifouled ready for re-launch
Osmosis Treatment Enquiry

Hot Vac Osmosis Treatment