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We recently moved into a new home with central vac. The vacuum unit is in the garage, as is typically the case, and seems to be in good working condition. I cleaned the "bucket" underneath and made sure the grid inside is free of dirt/lint etc.

It seems to me the suction when actually using the central vac system is not quite as powerful when compared to a regular vacuum. I can understand that the system is much "bigger" i.e lots of air in the pipes and much longer distance for particles to travel.

Is it expected that the suction should not be as strong as regular vac or am I dealing with a blockage or perhaps under spec vac?

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The [hvac] tag is for heating, ventilation and air conditioning. I don't know if that includes central vacuum systems. –  Dennis Williamson Aug 1 '10 at 4:25
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up vote 5 down vote accepted

I'm going to assume that the vaccuum was sized to the house, so it's not under-spec, although poor maintenance might mean that it's underperforming.

I'd suspect one of three things -- a blockage, a poorly performing pump, or a leak in the system.

If it's a blockage, unless it's right near the pumps, you'd have some areas with good pressure, and others past the blockage with poor pressure. (and the pump would be straining to keep up). You might be able to map out where a blockage might be by determining which ports have good suction, and which ones don't.

If it's a poorly performing pump, it's difficult to diagnose, but you might try listening for sounds of a straining motor and/or any odd smells. (I'm not so good in this field, so can't really say much more, a bad seal could cause just as bad as a problem, and I don't know if there's a good way to test for that.).

If it's a leak somewhere, the whole system won't be able to come pressure, so you'll have poor pressure everywhere. There might be additional dropoff at the leak if you were to try to map out which ports have worse suction than others, but as the suction is poor to start with, and some dropoff is standard for a pressuried system, it might be difficult to identify.

You might be able to better pinpoint a leak by intentionally clogging up the line, if it's run as a line with multiple ports off of it, rather than them all branching from one point. You'll need a two-way radio, baby monitor, or something similar. Put the transmitting end near the pump, and carry the receiving end with you. Open up the port, and intentionally block the tube on the side heading towards the pump. If there's no leak in that section, you should hear the pump straining.

Luckily, leaks are unlikely (unless perhaps if you've had an earthquake in that area), because I have no clue how you'd go about actually repairing it without tearing out the walls.

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I'm answering my own question here - maybe and admin can move this as a comment to my original question:

I did some more research on how to detect and clear blockage in central vac system. I disconnected the vac bucket from the unit and then used a regular vacuum at each outlet. At one of them, a huge amount of debris came out, including a "fabric softener" sheet and some other bits of dirt. This must have clogged the system enough to drastically reduce suction.

The change in power is unbelievable. Certainly more powerful suction now than my regular vacuum.

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It looks like you have two accounts (Pieter & Pieter Venter). Would you like me to merge them together? –  Eric Petroelje Aug 17 '10 at 11:03
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Check all the cover plates to make sure they seal correctly when the vacuum is running.

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The central vacs I've used have been more or less the same strength. If there's a remarkable difference, if it's really under-powered, then there's something wrong - either a blockage or too-small vac. But if it's nearly the same strength, just a little weak, there's probably nothing wrong.

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