Bayliss Autovents logo

01335 342981

Opening Hours

Monday- Thursday: 8:00-17:00
Friday: 7:00 – 13:00

Worldwide Delivery

Bayliss Autovents logo

01335 342981

Bayliss Autovents and Autovent Spares can be purchased online, worldwide.

Prices are shown without VAT, which will be added at checkout to UK and EU customers.


Lysander Works, Blenheim Road,
Airfield Industrial Estate, Ashbourne,
Derbyshire DE6 1HA United Kingdom

Phone: 01335 342981
Fax: 01335 343860



The Mk 7 unit has been made since the late 1980s. The present tube will fit all of the different types of Mk 7 – the Mk 7 Standard, Mk 7 Triple Spring, Mk 7 Hydraulicheck and Mk 7 Epoxy Powder Coated models.

The standard tube is filled with a wax that enables the window to be set to start opening between around 12°C (55°F) and 75°C (24°F). We also manufacture a tube that can be set to start opening the window at about 70°C. This is called a Mk 7 Orchid Wax tube and is available at a slight extra cost to the standard Mk 7 tube. Please contact us for details if you require this option.

See all autovent replacement tubes and spares

Mk 7 tubes open the greenhouse window a maximum of 30cms (12 inches) and will lift a total vent weight of approx 12 kgs (a load of approx 6 kgs).

MK 7 Power Tube

MK7 Autovent Power Tube

Alternative Shaped Plug on MK 7

Alternative Plug Mk7 Autovent

We use two types of plug on the end of the power tube and have illustrated them both. However, the type of plug does not affect the functioning of the tube and occurs because we manufacture the plugs on different machines. We illustrate them for information purposes only.

When you take the old tube out of the unit, you will have to damage the retainer washer that keeps the pin in place through the plug end of the tube. We always send out a new retainer washer with your new tube.

To illustrate the position of the washers and pin through the plug.

When you have inserted the new tube into the unit, follow the Mk 7 fitting instructions from Page 1, number 2… Place the Autovent in a cool place for half an hour…

When refitting your Mk 7 to the vent, make sure the straight links lie parallel to the glass in the vent i.e. the difference between the straight links and the glass in the window remains the same at both ends of the autovent even when the vent is close.

The Mk 7 unit, showing correct fitting to the vent

The photo shows the Mk 7 operating the vent when the window is semi-open. When the vent is completely shut, it is VERY IMPORTANT that the gap between the straight links and the glass in the vent is the SAME at BOTH ENDS.

This is very important because if the straight links do not lie parallel to the glass in the vent, part of the lifting force is wasted trying to push the vent against the hinge. This can result in severely overloading the unit and reducing its effectiveness and life. It also invalidates the guarantee.

All Mk 7 tubes are date stamped to show the month and year of manufacture.

Spares available for Mk 7 unit sold separately (contact us for price details)

Triple Spring Conversion Kit to enable a Mk 7 standard unit to be changed into a triple spring

Long Rivet, Short Rivet, Short Spacer, Long Spacer, Retainer Washer, Plastic Washer

Hydraulicheck Tube