I want to pump water between two containers using a pump and solenoid valves.
Unfortunately I have only able to find 6/12/24v solenoid valves that are one-way. With a bi-directional pump and solenoid valve I could pump the fluid in either direction easily by simply reversing direction of the pump.
Are there two-way solenoid valves, or is there a way to modify 1-way ones? By taking out the gasket?
Prefer to be able to do 50ml/s
Yes, there are two-way valves. They tend to be expensive. Why not use two one-way valves?
I thought about that too, but I would prefer two-way valves if it makes things a bit less complicated and requires less parts and also less points of failure and leakage.
Could you link some two-way valves?
Actually found some cheap ones. This is for pneumatics, but I have found that pneumatic valves can work for liquids as long as it's compatible with the seal.
With the right type of pump, that may be possible with 4 check (non return) valves. Is the pump higher than the tanks?
Some examples.
Also bear in mind some of the better ones can have the solenoid block swapped to cater for different voltages.
The fluid to be pumped can make a major difference to the type you need to select as the main unit.
Especially where flammable or corrosive elements are concerned.
Your pump flow rate might also play a large part in the selection too !
Thanks everyone, glad to see there are options out there.
What I want to make is an automatic still film developing machine that pumps rinse water and developing chemicals to and from the developing tank and also agitates.
I think my for purposes a simple 2-way valve will work, rather an arrangement of them. I still need to work out the routing of the valves, pumps, splitters, tubing and tanks. The pump can be placed below, level or above the source tanks but the developing tank is probably going to be above the pump.
I do not think those chemicals are corrosive, as daylight developing tanks can be bought in both plastic and RVS materials.
As for flowrate, aim is to be able to empty a 750ml developing tank within 10-15 seconds. If the developer and fixer take too long to pump out the pictures will get uneven development. The liquids will basically have the consistency of plain water.
Not familiar with development liquids so will take your word.
750 mL is not a lot so would suspect you will have plenty of choice in the valve at reasonable prices.
Flow rate of the pump will I suspect be the major contributor to any timing periods and they can be adjusted easily in your program.
Consider a small "over run " for the pump before it stops to allow for two things.
Any small increase in the amount of fluid.
Running dry can affect some pumps so use of a "self" priming or "peristatic" type pump.
Welcome! They make motor driven ball valves that will allow flow in either direction. What are the size of the tanks and flow rates? What are the pressures involved? How much time is the transfer? Are you using a peristaltic pump, also commonly known as a roller pump? If you are it will automatically turn off the flow when stopped. Show us what you have accomplished so far. Is this a school project? What other parts are involved? Can you post a sketch of what you expect?
We are not a free design house or a parts shopping source.
LOL Often we are without knowing it. 
There are some two-way solenoid valves available in the market, but they can be expensive and may not be able to handle a flow rate of 50ml/s. However, you can modify a one-way solenoid valve to make it bi-directional by removing the gasket as you mentioned, but this may not be a reliable or safe solution.
Another option is to use two one-way solenoid valves and two pumps, one for each direction of flow. You can control the direction of flow by opening the corresponding solenoid valve and turning on the pump. This solution would require more components, but it would be safer and more reliable than modifying a single solenoid valve.
With two 1 way solenoid valves you will probably need a check valve as they tend to open when the pressure if reversed. Post links to technical information on the hardware devices you are using.
I understand you're looking to move water between containers using a pump and solenoid valves. However, you've encountered a challenge – the 6/12/24v solenoid valves you found are one-way only. For bi-directional flow, you'd need a bi-directional pump and two-way solenoid valves. Modifying one-way valves by removing gaskets could be an option, but it's complex and not guaranteed to work.
Your flow rate goal is 50ml/s, which is substantial. Finding components that match your needs precisely is crucial. While two-way solenoid valves exist, their compatibility with your setup should be carefully assessed. Considering specialised suppliers or seeking expert advice could help you navigate this effectively, i had a similar issue with locating a bi-directional pump and found BM Engineering Supplies was really helpful with helping me find a solution.
Best of luck!
I use API for all my pneumatics and values. They have a variety of solenoid valves available, hope this helps!
What is the purpose in making a simple project so difficult. Automatic film processing has been done for many decades by moving the FILM film tank to tank, not the fluid.
Besides you have provided no way to stop contamination for one liquid with another.
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