Thanks for all the responses so far! Darn, I still haven't made up my mind about whether or not to buy the shop vac. And now the more expensive one has gone on sale. $179 down to $149, on sale till this Thursday. I still have a few more questions... 1) Sounds like it works well to suck out the muck and old leaves at the bottom of the pond. But does it ever clog up from the sediment? Or is the shop vac well suited for this purpose? 2) When most people use it, do they use it for their annual 'full cleanout'? Or do they use it for occasional cleaning while still leaving most of the water in the pond? I prefer not to totally clean and empty out my pond. I was planning to use it for it weekly in the spring for cleanup of muck (sucking out only 15% water at most at a time). Then once most of it is clean, I'd use it only on occasion. 3) Can I leave my fish in the pond while using it? I was planning to leave my goldfish in. Would this be a problem, suction too strong if they happen swim somewhat near where I'm cleaning??? 4) I was going to get a separate pump for doing water changes, but I guess I could just use the shop vac. Is it a hassle to have to set up each week? Maybe throwing in a pump hooked up to a garden hose is easier? Well I guess I'm going to have to decide asap, otherwise once it regular price, my husband will talk me out of it.

I've been working through building my own vac for a couple months, now (bought a house which came with a pond, so am working on upgrading, fixing, and cleaning). Some things have worked ok, some not so well, but maybe this'll help. For a pump, I'm using one of Harbor Freight's clear water pumps (1479-3VGA. 1" I/O), cause it wasn't expensive and it allowed me to do some experimenting without destroying a more expensive pump. Since this is a clear-water pump, it can't handle large solids (silt and mulm pass through without incident), so you'll need to build a filter for the front of it. My first filter consisted of an under-sink 20 micron water filter element (3" diameter, 10 - 12" long), housed in a specially constructed 3" PVC housing (previous owner had left the PVC). For tubing, I used standard 5/8" garden hose (had it laying around) that I modified for the job. This filter setup worked extremely well - especially for a wild stab in the dark - but it clogged way too quickly. Something like this would probably work well for a filter after the pump if the idea was to return the water to the pond and not the lawn/garden. My second filter used Waterbug Design's leaf trap as a guide. I again used 3" PVC (cause I had it), and made a filter element out of 1/4" hardware cloth formed into a cylinder. Since I had a lot of trouble fully sealing the first filter (against water/air leaks), I planned on hooking the filter to the pump with a length of tubing so that the filter could reside in the pond under the water. I also upgraded from the 5/8" hose to 1" tubing on the input side of the pump (still using the 5/8" hose on the pump output). This worked a *lot* better than the first filter, but it can still get clogged extremely easily in my pond - though I am trying to clean out 3 years worth of silt and mulm and leaves and rocks and pebbles and overgrown lilies as time allows (so my environment is probably worse than yours at the moment). One major pain about this "vac" is that the pump is not self-priming, so it was originally a huge ordeal to get the pump primed and keep the system as free of air as possible. So far, the best $10 I've spent was on a 1" check valve that I put on the output side of the pump - this helped out immensely in not having to totally re-prime each time the filter needed to be emptied. I'm in the "considering it" phase of making another attempt at the filter (I'm either going to make another filter, or cave and buy a decent vacuum). This time I'd go with 4" PVC and a larger screen element so that it wouldn't [hopefully] clog as quickly as it does, but my clogging problem is mainly caused by the pebbles getting stuck in the tubing or at the connection points rather than actual leaf/muck debris. My current vacuum configuration: 5' length of 1" PVC, connected to a 10' length of agricultural suction hose (basically a 1" clear hose with brass fittings on the ends), which connects to the filter, then a 6' length of 1" braided vinyl hose from the filter to the pump inlet. On the output side of the pump we've got the 1" check valve, with a reducer and brass hose fitting, connected to a length of old 5/8" garden hose. Even through all this the pump generates significant vacuum/pressure potential - sucking up anything in it's way and generating a pressure at the hose output similar to house pressure. I did initially try a shop vac, but that filled up so fast that it wasn't worth the trouble to me. I also don't want to use a "mop" type of vac cause of all the sediment that would get stirred up - I wouldn't be able to see anything for a week! I've given serious thought to putting the fish and plants in a temporary holder and giving the pond a thorough cleaning, but it's just me doing this and I don't think I could get everything done in a weekend (there are some *big* rocks in that pond).

Well, I thought this problem had solved itself. The thing started well most of last year and until this week. I thought it had a stuck ring or valve, or a little bit of varnish from the modern gasoline. Anyway, I installed two champion CJ8 s, gapped to .025. And it started right off. Changing from NGK BMR4As Lot's of good comments on this thread. It's a little over my head. I'm assuming that if the composite camshaft gear breaks, it's definitely not going to run, correct? And further regarding this thing, is this gear failure always a fairly benign thing? That is nothing else gets bent or damaged when this thing goes? I had the case cover off to repair the inner gasket to prevent water from leaking into the crankcase, actually I don't think it ever went into the crankcase, but it eventually would not hold water even to mow the yard once. I then, wasn't aware of this issue with the composite gear and I'm not totally sure if it has the composite or not. I seem to remember looking at a brown fiber gear-looking thing. But I'm not sure. Thanks for all the comments, and I think it's just the spark plugs causing this problem. Although I'm not sure why long cranking worked to get it to start. Anyway...Cheers!

jencjudd: Your builder's response from the central vac installer clearly indicates improper installation techniques. It sounds like the installers either are not using gradual sweeps in the tubing, or the power unit is undersized. I can't even imagine how in the world a hose gets "hung up" with proper installation. LOL! Are they using an oversized pipe diameter?! There are no sharp turns (not supposed to be anyway) in the piping. Here is the proper translation to their response: "The HAH takes extra time and effort to install and I actually have to use my brain to figure out the configuration for a main trunk line and still have enough piping for hose housing that doesn't interfere with the trunk line. I have a much larger profit margin on Beam CVs.". I'm sure at some point they will also throw in my favorite phrase....."I've been doing this for 30 years....". Can your builder use a different installer? This one wouldn't make me feel very confident. : /