Guide

Radon Fans, Manometers and System Maintenance

The manometer is the whole dashboard

Every properly installed system has a U-tube manometer fitted to the riser pipe: a small clear U-shaped tube holding coloured liquid. It is not measuring radon. It is measuring whether the fan is producing suction.

• Columns at different heights: the fan is pulling. Normal
• Columns level with each other: no suction. Either the fan has failed, lost power, or the pipe is blocked
• Reading noticeably different from its usual value: something has changed. A partial blockage, a leak in the pipe, or a fan losing capacity

Photograph the manometer on the day the system is commissioned and keep the photo. The absolute number varies between installations and is not comparable to anyone else's; what matters is the deviation from your own baseline.

What a failure looks like

Radon fans usually do not fail dramatically. They get quieter, then stop. Because nothing about the house changes visibly and radon has no smell, a failed fan can go unnoticed for a very long time, and the house returns to its pre-mitigation levels within hours.

Signs worth acting on:

• Manometer columns level when they used to be uneven
• The fan has gone silent, or has started making a new grinding or rattling noise
• A tripped breaker or a switched-off disconnect near the fan, which is a surprisingly common cause
• Visible damage to the pipe, or a section that has come apart at a joint
• In deep cold, condensate frozen in an exterior pipe run, which blocks it temporarily

Some systems have an audible or visual alarm on the fan circuit. On a system without one, the manometer plus a note in your calendar is the substitute.

PA DEP's retest guidance

DEP's guidance on monitoring a mitigated home is direct: "Periodically look at the U-tube manometer... The second aspect of monitoring your system is performing a radon test, generally in the basement and preferably during the heating season, once every two years."

Two years is the interval, the basement is the location, and the heating season is the timing, because that is when levels run highest and a test is therefore most likely to catch a problem. A short-term kit costs about fifteen dollars, so this is a trivially cheap habit relative to what the system cost.

The realistic maintenance schedule

When	What
At install	Photograph the manometer, file the post-mitigation test report, note the fan model
Every few months	Glance at the manometer. That is it
Every two years	Short-term test in the basement during the heating season, per DEP
Every 5 to 10 years	Expect to replace the fan. Retest after replacement
After any foundation, HVAC or major renovation work	Retest. Changing the building changes its pressures
After a power outage	Check the fan restarted and the manometer looks normal
Before selling	Retest, so you have a current number to hand a buyer

Replacing a fan

Fan replacement on an existing system is usually straightforward, because the pipe, route and termination are already there. Two things are worth insisting on.

The replacement should be matched to the system, not just to the old fan's physical size. Fans differ in how much suction they produce against resistance, and a system designed around a particular curve will underperform on a mismatched unit. And a retest afterwards is not optional, for the same reason it was not optional at install: the number is the deliverable.

In Pennsylvania, work performed for compensation requires DEP certification, which applies to service work as much as to the original install. See choosing a contractor and what a homeowner may legally do.

What it costs to keep running

A radon fan runs continuously and draws power in the range of a household light bulb, so the electricity is a small ongoing line. The system also removes some conditioned air along with the soil gas, which has a modest heating and cooling cost; good sealing at the suction point and around obvious floor openings keeps that small. Fan replacement every five to ten years is the only real recurring expense. Full ranges on what it costs.

Common questions

How do I read the manometer?

It is a U-shaped tube with coloured liquid. When the fan is running and pulling, the two columns sit at different heights. When the fan has stopped or the pipe is blocked, they level out. Note the normal reading when the system is commissioned, because a change from that baseline is the useful signal, not any particular number.

How long does a radon fan last?

Commonly five to ten years of continuous running. They are a wear item, not a permanent fixture. Replacement is a modest cost and is usually a straightforward job on an existing system.

Can I turn the fan off to save electricity?

No. The fan holds the space under the foundation at lower pressure than the house, and that difference disappears within hours of switching it off. The saving is small and the system stops working.