DIY Silt Vac - How to Build Your Own

Used for vacuuming silt out of the pond.


  • Small size fits head size rocks very well.
  • Can get into tight places.
  • Brush lossens algae and muck on bottom.
  • Small size means strong vacuum. Very much like using a shop vac without the disadvantages.
  • Fish seem less likely to dive under brush to hide and aren't vacuumed up.
  • Cheap.


  • Doesn't cover alot of ground.
  • Small size means more likely to clog, but we've been impressed how it hasn't clogged as much as expected.

What's silt?

Silt is composed of very decomposed organic matter and clay. These particles are very small, in the 2 micron range. They can be filtered out but the amount present even in "clean" ponds would require the filter be cleaned far more often than any ponder would consider useful. The best method of removal is to pump water out of the pond drawing it from the bottom so silt is carried away too.

Water loss from vacuuming.

Since water is pumped out of the pond expect about a 10% loss in a typical 3' deep pond. The more shallow the pond the higher percentage of loss.

The waste water can be reclaimed and put back into the after sitting in a holding tank for 24 hours. The silt will settle to the bottom of the holding tank and the top 90% of water can be pumped back into the pond. But this requires a fairly large holding tank, about 10% of the pond's total volume. Most ponders will prefer to pump the waste water into the garden and replace the water loss in the pond. This also does a 10% water change which many ponder routinely perform anyway.

Remove large matter first.

Because waste is being drawn into and through the pump it's likely clogs will occur. The main problem comes from string algae and leaves. The Silt Vac does have a leaf catcher that will stop leaves and large chunks of string algae from getting into the pump. But if the pond has large amounts of leaves or large chunks of string algae clogs are still likely in the vac head. Ponds with these conditions should be vacuumed first with a Muck Mop or other device. This will make vacuuming silt go much smoother and faster which means less water loss.

The leaf trap on the Silt Vac can be used to remove large matter. It totally depends on you and your pond. Some people may have no string algae and just fine silt. Some people may not think emptying the leaf trap every few minutes is a problem, other people would be very unhappy. The larger the pond though the more useful it is to remove large matter first. In smaller ponds just using the Silt Vac may be fine.

What pump to use?

It is possible to vacuum silt using you existing pond pump. You'll need a fitting on the intake which isn't available on most pumps. We use sump or utility pumps. Available in most hardware stores and fairly inexpensive, most less than $100. They're portable and designed to pass waste water. Problem again is most, if not all, of these do not have intake fittings. Our Pump Intake solves this problem for at least one pump, the 1/6 HP FloTec Tempest II Pump, model FPOS1250X.

Requried Equipment

1/6 HP FloTec Tempest II Pump, FPOS1250X. No other pump will work without modifying the plans.

A swimming pool extension pole. If only a short handle is needed, say less than 6', a piece of 1-1/4 PVC Sch40 pipe can be used. We use a 4' piece of PVC in our small pond which has very tight quarters and it works great. We use a 16' swimming pool pole in our largest pond.

A hose with 1-1/4" slip fittings on each end connects the pump/leaf trap to the brush. A 1-1/4" swimming pool vacuum hose will work pretty well. Cut the ends off and screw on 1-1/4" PVC Female Adapters (slip x female thread) on each end. A little silicone caulk helps seal the hose/fitting connection and also lubricates the threads because it's a very tight fit.

There's 2 basic parts that need to be built.

The leaf trap bolts onto the bottom of the pump.

Build Instructions

We've found this brush vacuum head the most fish safe choice.

Build Instructions