Yes, you normally can, and as a tenant, it is your responsibility to do so.
REGULAR MAINTENANCE (Tenants' Responsibilities):
In Hertfordshire, the water is very hard. This means that for the normal everyday running of your drains you will regularly need to use domestic drain cleaning products that you can purchase at the supermarket. It is your responsibility as a tenant to unblock the drains. If you are unsure or unable to do this yourself, then you will need to ask a friend or family member to help you, or you will need to hire a contractor at your own expense.
When there is a bad drain blockage and your domestic drain unblocking solution does not work, then it's possible that the drain under the manhole in the garden (or on the road) is not draining, the issue is most likely with the main sewage drain in that case, which is the responsibility of the council/local water supplier.
As the first port of call in those circumstances, please contact https://www.thameswater.co.uk/help-and-advice/drains-and-sewers/blockages and ask them to visit to "unblock the communal manhole".
If the issue has not been resolved once they have been, then please fill in a repair request on our website (Let Me Properties), clearly stating that you have followed the steps above to no avail, and we will then seek permission from your landlord to send in a contractor to clear the manhole (as long as it is definitely on the rented property and is not a communal drain).
Remember, if you report an issue to us and it turns out to be something that you should have done yourself or it is something that is caused by your (or your visitors) actions or failure to act, then you will be liable for the contractor charges.
For more information on the suggested steps above, you can search online to find articles that might be helpful. Our advice is provided in good faith, without any liability accepted by us. You should follow any suggestions with care and attention and if you do not have the skills or know-how required to carry out your tenant-like responsibilities then you ask a competent friend or hire someone to help you.