I have used several of those and decided not to buy any more parts for them to keep them working. Slowly they have all been getting emptied into cheap calibrated 1 quart sprayers and when emptied rinsed and recycled. If you are concerned about a lot of the fertilizer draining out at application you might want to recycle it by using any thing for a tray under the pots and dumping it back into the watering can or storage container. Just a thought for when it stops working. My fertilizer expense doubled over the last year with an eighth of the plants and that was the best thing I thought of to help a bit.
Grimmy