A wet spot under the tank outlet, or a steady drip at the sump fitting after you fill, is usually a gasket that is on the wrong side, a bulkhead that was cranked down until the poly deformed, or a flange clamp that was never seated on its gasket. None of those need a new tank. The trick is knowing which style of fitting you have, because a bulkhead, a bolted tank flange and a manifold flange joint each leak for a different reason.
Drain the tank below the fitting and rinse it before you pull anything, and wear gloves and eye protection; sump fittings hold concentrated product.
1. Find out which joint is leaking
- Drip from between the tank wall and a big poly nut — bulkhead fitting. Gasket is on the wrong side, is cut, or the nut is not snug.
- Weep around a ring of bolt heads on the tank wall — bolted tank flange (Banjo BF or MBF series). Bolts unevenly torqued, gasket shifted, or the tank wall is not flat under the flange.
- Drip at a clamp joint a few inches from the tank — manifold flange connection. Missing or pinched gasket, clamp not centered, or a standard port flange mated to a full port flange.
- Leak at the threads of the fitting screwed into the bulkhead — thread sealant or a cracked poly female thread from a stainless male fitting run in too hard.
- Crack radiating from the fitting through the tank wall — overtightened bulkhead, or a 3" bulkhead carrying the weight of an unsupported pump and plumbing. That one does need a tank repair.
2. Why it fails
Poly tank walls flex when the tank fills, and the fitting has to flex with them. A bulkhead seals with its gasket against the inside wall, under the flanged head of the body; the nut on the outside just holds it there. Put the gasket under the nut instead and the seal is on the wrong side of the wall and will weep as soon as the tank loads up. Overtightening is the other killer. Poly threads strip, the flange head dishes, and the gasket squeezes out instead of staying flat. Tank makers call for hand tight plus about a quarter turn with a wrench, then a check that the gasket has not crept. Bolted flanges fail the same way when one bolt is pulled down ahead of the others. Manifold flange joints are simpler: two matching flanges, one gasket, one clamp. They leak when the gasket is left out, folded over, or when someone tries to mate a 2" standard port (M200, 1-1/2" bore) to a 2" full port (M220, 2" bore). Banjo is explicit that full port only mates with full port.
3. The part for your tank
| Fitting | Use it for | Part |
|---|---|---|
| Bulkhead, 1-1/4" and 2", Ace / Den Hartog tanks | Small sumps, return and agitation ports | Den Hartog 10918 1-1/4" bulkhead (2-1/4" hole), Den Hartog 10508 2" bulkhead (3" hole) |
| Bulkhead, 1/2" to 2", EPDM gasket | General tank ports | Green Leaf TF050, TF075, TF100, TF125, TF150, TF200 |
| Bulkhead, 3" | Main sump outlet | Banjo TF300 (4-1/2" hole); spare gasket TF300G or Green Leaf TF300G |
| Bolted tank flange, 3" FNPT both sides | Big sump outlet on a flat wall | Banjo BF335 3" bolted tank flange, 3-1/2" bolts |
| Bolted manifold tank flange, flange out | Sump straight onto a manifold system | Banjo MBF200 2" standard port, MBF220 2" full port, MBF300 3"; bottom-drain versions MBF220BD, MBF300BD; flange-both-sides MTF220BD, MTF300BD |
| Manifold gasket | Every flange joint | M101G 1", M201G 2" standard port, M221G 2" full port, M301G 3" |
| Manifold clamp | Light duty | FC100 1", HDFC200, HDFC220, HDFC300 |
| Manifold clamp, bolted stainless | Heavy hose or pump hanging on the joint | Banjo FC220B 2" full port, FC300B 3" |
| Flange adapters off the tank | Thread or hose from a flange | M200MPT, M200FPT, M220MPT, M220FPT, M100MPT, M100FPT |
4. Installing it so it stays dry
- Bulkhead: gasket goes on the body, inside the tank, against the wall. Nut goes outside with no gasket. Tape the body threads so the nut turns smoothly. Hand tight, then a quarter turn, and hold the body so it does not spin and drag the gasket.
- Check the hole size before you buy. The Den Hartog 2" bulkhead wants a 3" hole, the 1-1/4" a 2-1/4" hole, and the Banjo TF300 a 4-1/2" hole. A hole that is too big lets the gasket squeeze into the gap.
- Bolted flanges: snug all bolts by hand, then tighten in a star pattern in small steps. Do not pull one bolt down and move on. Stop when the gasket is evenly compressed, not when the wrench stops.
- Manifold joints: wet the gasket, seat it in the groove on one flange, bring the flanges together square, center the clamp over both lips and tighten until the clamp bottoms. A clamp that is cocked to one side will leak on that side.
- Full port and standard port do not mix. If the flange faces are different diameters, you need a reducer flange such as the M220200CPG, not a bigger clamp.
- Use PTFE tape, not pipe dope, on poly threads, and never run a stainless male fitting into a poly bulkhead with a pipe wrench.
- Fill the tank with water and let it sit overnight before the first load of product. Tank makers recommend a 24-hour water test after any fitting work.
- Recheck fittings after the first fill and again after the first week. Poly relaxes.
Not sure which fitting or gasket? Send a photo of the fitting from inside and outside the tank, with a tape across the hole to sales@spraycenter.com or call (509) 838-2209.
Spray Center Electronics stocks Banjo, Green Leaf and Den Hartog bulkheads, bolted tank flanges, manifold flanges, gaskets and clamps in Spokane, WA. Part numbers here come from the manufacturers' parts sheets; if your fitting does not match what is described above, send a photo and we'll match it before you order.