Cleaning with TSP isn’t as common as it once was, but it’s great for cleaning surfaces before painting. This powerful cleaner is great for removing oil, grease, and stains and it can be used for both the interior and exterior of your house. Getting rid of oil and grease before painting matters more than most DIYers think — contamination is the main cause of fisheye problems in paint.
I've seen what happens when that step gets skipped, or done half-heartedly. On one job, kitchen walls hadn't been washed enough before painting — there was more grease built up than anyone realized. The new paint went on looking fine, but it didn't stay that way. It started curling off the wall, almost like water beading and sliding off a freshly waxed car. The paint just couldn't grip the surface underneath. That's the whole reason this step exists: paint needs something to hold onto, and a film of kitchen grease is exactly what stops it from doing that.
But there is a reason TSP itself isn't used as much these days, and the reason is in its name. Read on to learn more about TSP and how to safely use it.
What is TSP?
Trisodium Phosphate (TSP) is a white granular powder that is commonly used as a cleaner and detergent. It works by creating an alkaline solution when it’s mixed with water, which effectively breaks down dirt and grime on painted and other surfaces.
TSP contains between 75-80% trisodium phosphate and 20-25% Sodium Carbonate. This makes it very versatile for cleaning different surfaces, such as decks or walls, both indoors and outdoors.
The use of TSP has declined since it contains phosphate, which is a nutrient for algae and can cause environmental problems and affect aquatic life. This has resulted in stricter regulations on the use of TSP by many states and cities.
Although it’s an effective cleaner and stain remover, TSP should be used with caution since it can be harmful to you if not used right.
TSP Mixing Ratios
The right concentration depends on the job. Here's what to mix for each situation:
| Job | Mixing ratio |
|---|---|
| General cleaning | ¼ cup TSP per gallon of warm water |
| Heavy grease / pre-paint prep | ½ cup TSP per gallon of warm water |
| Mildew and mold (exterior) | 1 cup TSP + 3 quarts warm water + 1 quart bleach |
Start with the general ratio if you're not sure how dirty the surface is — you can always mix a stronger batch if the lighter one isn't cutting through the grime.
Is TSP Safe To Use?
As long as you wear proper gloves and safety glasses, TSP is safe to use. Use gloves such as nitrile gloves or similar.
When you mix TSP with water then don’t inhale the dust and wear a dust mask if needed.
If you get it in your eye it can cause severe irritation, redness, tearing, and blurred vision and may cause transient injury to the cornea.
If that would happen then flood with plenty of water with eyelids held open for at least 15 minutes and get medical attention promptly.
If you inhale the dust it can cause nasal and respiratory irritation. If symptoms develop then seek immediate medical attention.
Prolonged or repeated contact might dry the skin and other symptoms might be redness, burning, cracking of the skin, and skin burns.
Wash your hands after use with soap and water and launder your clothes before you use them again if they have been in contact with TSP.
Surfaces You Should Never Use TSP On
TSP is strong, and that strength can damage certain surfaces:
- Glass — it etches the surface if left on too long or not rinsed properly.
- Aluminum — TSP's alkalinity can corrode bare aluminum.
- Varnished or lacquered wood — it will strip the finish right off.
If you're not sure what a surface is made of, test TSP on a small, hidden spot first.
How Should TSP be Prepared and Applied?
Mix your TSP using the ratios above in a bucket of warm water. For most walls, the heavy-grease ratio (½ cup per gallon) is the one I reach for — better to cut through grease properly the first time than to find out halfway through that the wall isn't actually clean.
Here's the process I use:
- Protect the floor with a drop cloth — TSP solution drips, and it's not something you want soaking into carpet or hardwood.
- Apply the solution. A sponge works fine for most walls; for bigger areas I'll sometimes switch to a large brush to cover ground faster. Either way, work the solution into the surface rather than just wiping it on.
- Rinse with a clean, damp sponge as you go, before the solution dries on the wall. Change your rinse water once it gets dirty — you're not accomplishing much if you're rinsing grease back onto the wall with dirty water.
- Let it dry completely before you paint. A damp wall traps moisture under the new paint film, which causes its own problems down the line.
If you're using it to clean surfaces with mildew and mold, which is common on the exterior of your house or outdoor furniture, use the mildew ratio from the table above. Repeat the procedure if necessary and rinse the area well.
This is the advantage this concentrated product has compared to pre-mixed detergents in bottles. It’s great for larger surfaces such as walls, both indoors and outdoors.
It’s also available as a concentrate in liquid form which is preferable since you don’t need to worry about inhaling the dust when mixing.
Are There Alternatives to TSP?
Two products that are excellent alternatives to TSP.
Honestly, on most jobs these days I reach for a premade solution rather than mixing powder myself. It's more practical — apply, then rinse, no measuring or mixing required, and no dust to worry about inhaling.
| Product | Rinse required? | Notes |
|---|---|---|
| Dirtex | No | Same maker as TSP, gentler on skin, still etches glass |
| TSP-PF (phosphate-free) | Yes | Same cleaning power as TSP, without the environmental concerns |
| Krud Kutter Prepaint Cleaner | No | Widely available, marketed as a direct TSP substitute |
| Simple Green All-Purpose/Heavy Duty | Yes | Good general degreaser, less aggressive than TSP |
| Mr. Clean / Pine-Sol / Lysol / Formula 409 / Clorox / Mean Green Multi-Surface | Varies by product | Fine for light cleaning; less effective on heavy grease than a dedicated pre-paint cleaner |
Dirtex, from Savogran (the same manufacturer that makes TSP), is the one I use most — no rinsing needed and it's gentler on your skin. But as with TSP, don't leave any Dirtex on glass surfaces, since it can etch it too.
Where can I find TSP?
You can find TSP at most hardware stores, home improvement stores, and supermarkets, alternatively, you can order it online from retailers like Amazon or Walmart.
It’s usually sold in the form of a white powder but it can also be bought in a concentrated liquid form.
Can I use TSP for regular cleaning?
Yes, TSP can be used for regular household cleaning. It can be used to clean and degrease surfaces such as painted surfaces, walls, floors, doors, trim and appliances. It is especially effective in removing greasy or oily residues from surfaces.
It’s important to dilute TSP with water before use according to the instructions and it’s important to rinse off all surfaces with clean water to prevent any residue from being left behind.
Also, TSP shouldn’t be used on glass surfaces. When it has been applied on glass and not been rinsed off properly it can cause etching.
Should you wash walls with TSP before painting?
It depends on what condition the walls are in, if it’s walls in your kitchen or bathroom then I would recommend cleaning them.
If the walls are exposed to grease, moisture, or smoke then you should definitely clean them with TSP before painting.
That being said, if the walls don’t have anything like that on them and they’re in good condition then you shouldn’t need to clean them before painting.
Areas that hands usually touch should be cleaned since your hands leave behind oils and dirt. But other areas that don’t get touched very often you probably don’t need to clean before painting.
If you’re unsure then use your hand over the wall and see if it gets dirty, or use a rug/cloth with some detergent on it and wipe a small area and see if it gets dirty.
Can TSP go down the drain?
Diluted TSP in small quantities can be disposed of in the sink. Large amounts must be disposed of in accordance with local state and federal regulations.
Phosphate is bad to pour down the drain in large amounts because it can cause eutrophication.
Eutrophication is an unnatural increase in the level of nutrients in a body of water, which can lead to an overgrowth of algae and other aquatic plants, resulting in a decrease in water quality and oxygen levels, leading to fish and other aquatic life death.
TSP FAQ
Do you need to rinse after cleaning with TSP? Yes, always rinse regular TSP with clean water. Leftover residue can interfere with paint adhesion and, on some surfaces, cause etching or discoloration. (Rinse-free alternatives like Dirtex are the exception — check the product label.)
Is TSP the same as borax? No. Borax is a mild, naturally occurring mineral cleaner, while TSP is a much stronger alkaline degreaser. They're both used in cleaning, but TSP is the one you reach for on heavy grease and grime — borax won't cut through that the same way.
Can you mix TSP and bleach? Yes, and it's actually a standard combination for mildew — see the mildew ratio above. Just never mix TSP (or bleach) with ammonia-based cleaners; the combination produces toxic fumes.
Why is TSP restricted in some states? The phosphate in TSP is a nutrient for algae. When it washes into waterways in large quantities, it contributes to algae overgrowth and oxygen loss in lakes and rivers — see the disposal section above. A number of states restrict or ban traditional TSP for this reason, which is part of why phosphate-free alternatives like TSP-PF exist.
How long should you wait to paint after washing with TSP? Let the surface dry completely — this usually just means overnight, though it depends on humidity and airflow. Painting over a damp wall traps moisture under the new film and can cause adhesion problems down the line.
Conclusion
In conclusion, TSP is a powerful cleaning solution and stain remover great for prepping surfaces before painting and other cleaning jobs as well.
Although, it needs to be used with caution and proper safety equipment, such as gloves and safety glasses while you’re working with it.
Remember to not use it on glass or leave it on for longer periods of time since it can etch the surface.
Alternatives to TSP, such as Krud Kutter or Dirtex, can also be used for prepping surfaces — and honestly, a premade solution is what I reach for on most jobs these days simply because it's more practical: apply, rinse, done. It's also better for the environment since these products don't carry the phosphate concerns that come with traditional TSP.
