Patch a hole in top of plastic oil tank?

Temple83

Recently I added a Kingspan Watchman sensor to the top of my plastic oil tank, but after week or so it stopped picking up changes in the oil level.
I'm fairly sure i've put the sensor in the wrong location and want to move it, however the cap that originally covered the hole also took the tread with it when I took the cap off so I cant just screw it or a replacement cap back on.

Does anyone know of any solutions for being able to patch a hole in the top a plastic oil tank?
There are no issues with the rest of the tank so seems a bit extreme to replace the entire tank if I can get away with not.

tacpot12

The tank is likely to be polyethene, which id difficult to get things to stick to. 

I'd suggest that you try to find out what the tank is made of for sure, and then try to get a peice of compatible material to cover the  home, and use the right glue to stick a patch over the hole. If it is polyethene, this link migh thelp: Don't glue Polyethylene, BOND Polyethylene | tbbonding - The Adhesive Solutions Site

Rodders53

Kingspan might do a 32 mm diameter hole cover replacement / seal ? 
https://www.fueltankshop.co.uk/32mm-gauge-hole-plug-for-harlequin-oil-tank/p4937 is one for Harlequin tanks and might even be suitable for the job?

The Energy... Heating Oil.. sub forum may have people with more experience of alternative ways ?
https://forums.moneysavingexpert.com/categories/lpg-heating-oil-solid-other-fuels

They may also be able to advise if there's a fix for the lack of signal (distance, loss of pairing, battery general interference) on the Watchman.  I assume you've read the manual, section 10 especially?

Watchman in the wrong place on the tank is more likely to give a no echo fault code readout, I'd expect?

Mistral001

If you feel confident enough, you could try welding another piece of polythene of the same thickness as tank material over the hole.    You need a fairly low wattage soldering iron.  The welds would have to be formed around the perimeter of the piece you are welding to the tank.  I have done this a few times with plastic buckets and the like.  Make a few practice welds on scrap pieces of plastic before attempting it on your tank. Do not attempt if you are not confident as you could easily make a bigger hole in your tank.

Here is a video:Delboy's Garage, Simple skills # Plastic welding - YouTube