Filling, Venting, Draining
Filling and Make-Up Valves
Filling and make-up fittings close off the top of a coolant reservoir and open it for filling and topping up. The category lists 56 items, mostly plastic filler plugs from the BS, BSF, BSM and BSFM series. Threads run from G 3/8" through G 1/2" and G 3/4" up to G 1", and metrically from M 16x1.5 through M 18x1.5 and M 20x1.5 up to M 22x1.5. Depending on the version, the plug carries an air filter, a dipstick, or both.
The designations describe the fit-out: BS is the plain filler plug without an air filter, BSF adds the filter, BSM the dipstick and BSFM both. The filter keeps dust out of the reservoir when air is drawn in as the level drops, and the dipstick shows the fill level without opening the loop. Plastic keeps copper alloys out of the wetted path and resists water-glycol, so this design creates no material conflict in loops piped in stainless steel or PP.
- 56 items
- 2 manufacturers
- Net prices plus VAT
Buying guide
How to choose Filling and Make-Up Valves
What matters when choosing: properties, comparison and typical applications.
Technical advantages - filling and make-up valves at a glance
System comparison & product overview
The four series compared
| Series | Air filter | Dipstick | Available threads | Material |
|---|---|---|---|---|
| BS | no | no | G 1" | plastic |
| BSF | yes | no | G 3/4", G 1" | plastic |
| BSM | no | yes | G 1/2", M 18x1.5, M 20x1.5, M 22x1.5 | plastic |
| BSFM | yes | yes | G 3/8", G 1/2", G 3/4", M 16x1.5, M 18x1.5, M 20x1.5, M 22x1.5 | plastic |
Typical applications
- Initial fill of a coolant distribution expansion tank with water-glycol mixture
- Topping up after maintenance work or evaporation losses
- Checking the level on the dipstick without opening the closed loop
- Pressure equalisation at the tank through the air filter as the level varies
- Retrofitting existing reservoir lids to a version with filter and dipstick
- Replacing metal plugs with plastic in loops built from mixed materials