Goods must be fit for the purpose, of satisfactory quality and as described, under the SGA, sections 14 and 15.
If you purchased the bath only recently, you have the right to reject it and get a full refund.
If you have had for a while (undefined, sadly) you are entitled to a replacement or repair.
However, within the first six months there is a presumption that the goods are inherently faulty and you should get a refund or replacement (your choice). Do not accept a repair at this early stage.
Remember - your contract is with the company you bought the bath off - not the manufacturer. Do not be fobbed off.
You may need to look at the Supply of Goods and Services Act 1982 if the problem is caused either wholly or in part by shoddy workmanship during the installation.
Don't be frightened of pursuing this - it is important to keep all receipts, guarantees and a written diary of events. Include date of purchase, date of delivery, date of installation, and most importantly a record of contact detailing all phone calls and contact with the vendor. You may need to show you have acted fairly and reasonably, and the vendor has not.
Should you need to go to court it can be done through the Small Claims' Court for little cost, and can be initiated online.
Here is the Sale of Goods Act - print out the relevant sections if you want to:
http://www.netlawman.co.uk/acts/sale-of-goods- act-1979.php?pageContentID=15590
And here is sound advice and contact numbers:
http://www.dti.gov.uk/consumers/fact-sheets/pa ge38311.html