Note: Solve the problem upstairs first ... the down stairs bathroom has a few more options. I would strongly suggest that you put a bathtub and shower unit or tile unit w/ shower upstairs even if the tube is smaller ... it still counts as a tub... making a full bathroom home . Plus expanding the vanity and larger mirror is a big plus (women need that viewing area) Placing a full bathroom down stairs is not a good selling point but a nice half bath with shower and storage area down stairs is a nice selling point.
http://www.dimensionsguide.com/bathtub-dimensions/
http://www.lowes.com/pd_89243-95384-0133.017.020_4294857181_4294937087_?productId=3073499&Ns=p_product_prd_lis_ord_nbr|0||p_product_quantity_sold|1&pl=1¤tURL=%2Fpl_Tubs_4294857181_4294937087_%3FNs%3Dp_product_prd_lis_ord_nbr%7C0%7C%7Cp_product_quantity_sold%7C1
Small Space Bath Tub
Are you afraid that your bathroom is too small to fit a bath tub? Worry not, because there are a lot of big ‘Lilliputian’ solutions that would enable you to still have the luxury of a bath tub even if your bathroom is less than 50 square feet. A lot of bathroom fixture manufacturers now sell (off the shelf) undersized bath tubs. There are also a number of companies willing to design a tub especially for your bathroom’s dimensions. You can even design your own bath tub and have it professionally made and installed.
Planning for and buying a small space bath tub, however, may not be as easy as it sounds. There are a number of functional and safety considerations to keep in mind. Here is a complete guide to buying (or designing) a small space bath tub.
Go small
The standard bath tub size is about five feet long and about 32 (sometimes 30) inches wide. It might be difficult to find smaller versions in non-specialty stores, but it is certainly not impossible. If you do not see any regular rectangular bath tub to fit your room’s dimensions, consider a corner tub – most of them are less than five feet in length. For example, the economy McKenzie bath tub (manufactured by American Standard) is only four feet long. Made of enameled steel, you can get it for a very low price from Home Depot and other major bathroom fixture retailers. There is also the popular Kohler Mayflower corner bath, also designed for tight rooms. It is a little pricier, but it comes in colored finishes.
Personalize a tub for your bathroom’s dimensions
Do you want your small space bath tub to have specific dimensions? Then have one custom-made to fit your bathroom’s specific dimensions. Contact bathroom contractors in your area and have the space surveyed. Most companies offer free estimates – be sure to call around first before signing up with a contractor, or you may be passing up great savings.
With some planning, you can even have a custom tub and shower combo built for your space to imitate units that can be bought ready made (they usually measure 29 5/8” x 31 ¾”

. These space saving units may cost a little more, but they sure do go a long way. Have shelves, soap dishes, and perhaps even a seat built into the unit to get the most out of the space.
Note: You can remove the floor and redirect the plumbing drain to the toilet and also add the flexible plastic water line (
http://www.ppfahome.org/pex/faqpex.html)
You should redo the flooring anyway for additional support ( I see the toilet is placed on a re-supported section of the floor) and better seal of flooring tile.
This tells me at one time something happen to the toilet drain system (should be looked into… could be a problem waiting to happen)
I used this to redo all the plumbing in my century old home (with turn off value at every junction works great and easy to install)
Chicago Architect daughter agrees...