A few suggestions and long-winded comments:
1) Ideally, your sump pump is tied into underground tile from a
perimeter drain system. When you get the water level in the sump
very low, then you can do some investigating to determine if this
is true. You should be able to see the circular cutouts in the
plastic sump basin where the tile connect to it. In a corner
installation, you will typically have 2 tie-ins with one tile
entering parallel to each of the two walls forming the corner.
2) If you anticipate heavy spring rains and/or you already have a
problem, then you want to force the pump to evacuate as much water
as possible from the sump. Set the float or override the float if
necessary. If you override the float, then you need to be in the
basement nearby to make certain that you don't run the pump dry.
You can override the float very easily - just get a piece of string
and tie up the float so that it can't lower (temporarily!).
3) The gravel bed under your concrete basement floor functions as a
buffer zone for water. When you evacuate as much water as possible
from this area and from the soil under your house, then you have a
cushion for the next storm. Generally, ground water must fill these
buffer areas before the water can begin to infiltrate your basement.
And with good perimeter drain tile and a properly functioning sump
pump system, you will usually be able to remove water from these
buffer areas fast enough to prevent them from overfilling during and
after a heavy rain. Think of the area under your basement floor as
a huge drywell. Note that this buffering function is dependent upon
how well your sump pump is evacuating water under the entire basement
floor and the surrounding soil. This will depend upon the depth of
the gravel under your basement, the existence and current quality
of the perimeter drain system, soil type, etc.
The more you lower the water level in these buffer areas, the more you
are paying in electricity for the extra cushion of safety that you
achieve. Personally, I feel that having the sump pump run more and
avoiding a basement flood is well worth the extra bit of cost. We
all pay for auto insurance, life insurance and home insurance. Setting
your sump float to the lowest possible setting is just one more form
4) You obviously have had a sump pump & float system which wasn't
functioning optimally. You also may have no drain tile feeding the
sump or a tile system which is clogged. If you have drain tile and
you continue to have problems, then a "Roto Rooter" type of company
may be able to come in and examine your tile system with a miniature
camera. They may also be able to clear some blockages in the drain
tile system, or locate areas of collapsed drain tile and address them
5) For now, you should set you sump pump to the lowest reasonable
water-level setting and see what happens. When the sump pit water
level is low, examine the pit to see if you have drain tile coming
into the pit. You can also hook up your old sump pump to function
as a second pump if there is enough room in the pit. Buy some cheap
flexible corrugated black plastic pipe so that the old pump can pump
water to a safe location outdoors via a basement window, or have it
drain into your basement drain or utility sink if you have city hookup
and not a septic system for your sewer drains. Remove the float from
the old pump and lock the remaining float arm in the "always running"
mode. Using the old sump pump will double your pumping capability
when you need it. This will provide you with valuable information
about how well you can alleviate you water problems via the single
sump pit that you have.
6) If you continue to have problems, then you must:
a) Clear blocked drain tile if that is a problem as discussed above.
b) Address all outside issues if possible. I have a very nice
neighbor who is uphill from me. He had one roof drain which was
dumping directly on the ground and the water was running onto my
property & eventually to my basement. He fixed the problem by
rerouting the water and helped me considerably. As you have
guessed in your situation, it is possible for your water being
dumped 6' from your house to still contribute to your problem.
Then again, maybe not.
The water entering your basement can be coming from far away, but
it can also be coming from roof water that you are dumping
6' from your foundation. The biggest problem about addressing
basement water issues is that we are forced to intelligently guess
about what is happening out-of-sight and underground.
c) You may need to install perimeter drains to dump into the sump pit.
This is expensive. You can cut cost by hiring moonlighters from a
basement company who will work off the books on a weekend. You
can do it yourself if you are ambitious. The cost of materials is
rather modest - this is labor intensive. Professionals will want
to do a "complete system", whereas you can experiment with
partial solutions. Adding drain tile along one or both of the two
walls that would "feed" you sump pump may help tremendously.
You can add drain tile in stages along additional walls as needed.
d) You may need a second sump pit and pump on the opposite side
of the basement. As above, this is a bit expensive to hire out,
but can be done rather cheaply. I intend to install 2 sump pumps
& pits this summer with help from my son. The cost for 2 will be
just a few hundred dollars since I already have perimeter drain
tile but no sump pumps.
e) Use caution when taking the advise of "professionals." Obviously,
it is difficult for those who sell basement waterproofing systems
to be objective when advising you. This is an industry which makes
a living through scare tactics and oversell. It is extremely common
for homeowners to pay $10,000 or more when the actual fix that
was needed could have been done for less than $1000.
Also, remember that a 5 year, 10 year or lifetime warranty may be
totally worthless if the company that did the work goes bankrupt,
changes hands, restructures, etc.
Even if you don't anticipate hiring such companies, it is extremely
worthwhile to observe how they operate when installing systems
for neighbors, friends and relatives. I have learned considerably
by observing in many such cases. The most recent example was
my next-door neighbor who probably paid between $8,000 and
$12,000 for a "total system" whereas he and I could have addressed
95% of his problem with just one half day's labor and $25 in materials.
From my observations, the folks who are "professionals" form
companys with extremely poorly paid "grunts" who do the heavy manual
labor and who are very poor at evaluating situations that they encounter.
Project supervisors aren't much more astute. Even the sales
reps and company bosses are rather obtuse in evaluating situations.
They are experts at following a scipt which involves over-engineering
every situation. Think of the car mechanic who will guarantee his work
when fixing an auto which has an engine which isn't performing optimally.
The mechanic is an expert at replacing spark plug wires, spark plugs,
air filters, pcv valves, etc. He is also an expert at remove fuel
injection systems or carb systems and sending them our for rebuilds.
Of course, when he replaces every replacable component in the fuel
delivery and ignition systems, the car will probably run much better than
before. But you may be paying $1200 for a problem which could have
been fixed for $50. I have seen auto shops which specialize in such
extreme approaches to every situation in which an auto runs poorly.
Sadly, the approach of almost ever "pro" toward basement water
problems is very similar.