Hello Matthew,
Many thanks for the confirmation.
So, the amount that is posted on the vendor summary account is then the net amount and you want to post the gross amount as expense on the water rates account.
Right?
Just tested this in the DEMF contoso environment from MS and the following could work.
Please check and confirm:
1. Open a GL journal in DEMF and disable the 'include sales tax' parameter
2. Enter a vendor invoice for example for 800 EUR.
3. Select an expense account and the item sales tax group FULL.
4. Select the tax group AP-EU
5. Post the invoice.
What you will get is something that looks as follows:

What you have to make sure is that your 'use tax receivable' account points to an expense account; the one that you use for water rates.
In other words, the account 130750 needs to be replaced with an expense account.
Then you can have the gross amount expensed.
The credit side is also ok.
The only things that might be a bit strange is the sales tax posting type that would be used for posting the additional expense on the water rates account but I don't think that this should be an issue.
Would be great if you could double check/replicate and let us know if this fixes your issue.
Best regards,
Ludwig