Water Pressure Drop

[Siegfried]

Hi, newbie on the Forum, looks very informative.

I hope you can help me. Here is the problem.

In our cottage we are using a 1/2HP pump to suck water through a 1 ½” (I.D.) pipe from the lake. There is hardly any rise to the line.
The intake hose runs about 100' with a 90 elbow to a rigid 3' pipe then to a another elbow to the foot valve in the lake.

This pump has a pressure gauge switch that cuts in at 40 psi and cuts off at 60 psi. I checked the pressure tank pressure back in May and it was very low.
So with the system emptied of water, I pumped the tank back up to 38 psi. It seems to be holding this pressure.

The pump was replaced last year by a plumber. I can not find on the pump any detail regarding flow rate. Which is puzzling.

Now we have very low water pressure intermittently. Sometimes there is no water at all. This is when the pump keeps going for 10 minutes or more.

When the pump does come on during normal usage of taps or toilets it seems to take quite a bit of time to get the pressure back up.

The pump runs for 5- 10 minutes before reaching cut-off. This seems long.

I checked our foot valve and this seems okay too.

I was thinking of digging up the intake hose and inspect it for leaks but it is buried under 2 feet of dirt for about 20 feet before it goes into the lake.

So then I thought I would replace it with a new hose and foot valve and thought that I could use a different size hose. Say 1” or something.

So what do think the problem could be?

Can I change the intake hose to a smaller diameter hose if this is the problem?

Thank you for any help you can provide,

Siegfried

[speedbump]

Smaller pipe will make it worse. If you have an air leak, you would have air in the house. Is the footvalve the only kind of filter you have on this pump?

I have seen small snails in a lake get pumped into a water system then grow up while living in the impeller to the point where they couldn't get out. Not the pump won't make much pressure. It also couldn't pump much water. This happens where the pump sits for quite some time without being used.

I would be getting a lake strainer. I have one on my website you might be interested in.
You can see it HERE

bob...

[Siegfried]

there is a sediment filter after the pressure tank.
I took the impeller section on the pump apart awhile ago and checked for clogs/debris.Everything looked good.
When the pump is going and I open the valve that is just before the filter, I get lots of water coming through.
Refering to your air in the house comment, I should explain the intake line.
The intake slopes down about 2 feet right outside the house. The water level of the lake is almost at gound level, due to rain. When I dug down to the pipe to make a 4' long trench, the water from the surrounding grass and the ground gradually filled it up. So this line is below the water table, so I might not get any air sucked in. Or not much anyway.
since this area is almost always wet, it is difficult for me to determine if there might be a leak in it because I would have a wet area around a leak.

I thought I might just try a bypass intake line to help diagnose the problem. That's why I thought about a 1" line as not many stores in my area had a 1 1/2" line in stock.

[ecpgroup]

a 1" line might make the pump cavatate its good practice to go one size bigger then the pump inlet for longer runs or larger if possible. now you have put some air in the p/v the pump has to overcome this pressure b4 it starts to put water into the tank. if the pump is worn ie neck rings gone,impeller worn,or cracked vulute then the pump will be well down on its cuve. 1/2hp is a small pump. is it a jet pump, turbine, screw type or single impeller as these all have diffrent pros and cons. you say some times no water! do you mean the pump is running but not delivering? gauge readings are what when this is happening. i find it hard that you have a air leak in the suction as this would be seen by the pressure droping on the gauge unless you have another check valve on the inlet or just after the pump.

you could try dipping a hose off the pressure side of the pump in to a bucket of water and see if the pump is pumping any air as this would casue it to not reach cut out pressure untill air is cleared.

all the best max

[jadnashua]

Have you checked your sediment filter? Is it plumbed so you can bypass it? You said you had plenty of volume before the filter. Sounds like the filter is clogged if I understand what you said.

[speedbump]

Define the pump for us.

bob...

[Siegfried]

Thanks for the replies,
It looks like a Jet pump that I saw a picture of here.
http://www.rittenhouse.ca/asp/product.asp?PG=1225
The pump is less then a year old. I was not present when it was decided
that the old pump was faulty and needed replacement. The previous pump was the same size. But the fault of loosing pressure started before that.

I will replace the filter and also try the bypass as it is plumbed with a filter bypass. This is going to have to wait until the weekend as this is at a cottage.
The pressure gauge on the pump will drop below its cut-in setting, almost to zero. The pump comes on immediately and water is being pumped.
It just takes quite a bit of time for it to come back up to cut-off.
This is resulting in very low pressure at the taps.

Of course, I'm dealing with "It wasn't like this before" phrase. So I'm trying everything I can think of.

[speedbump]

WOW do they have some high prices.

That is a shallow well jet pump. And if it's only that old, it should be pumping more water. I would have to think your screen in the well is getting badly plugged and needs changing.

bob...

[Siegfried]

Finally some success!
I ended up bypassing the main intake from the lake with a new piece of hose and voila! Good pressure all the time now.
I decided that the problem had to be in the intake side of things. Pressure tank was at 38PSI (empty), pump was new, no slow leaks in the house.
So instead of digging two feet down for 20 feet to check the existing intake line, I mearly cut the hose at the pump (this was due to the fact that the previous plumber had used a special glue on the fittings at the pump so I couldn't undo it), attached my new 1 1/2" hose, ran hose to a different location, so I wouldn't have to dig a new trench, hooked it up to another extension that goes into the lake, cleaned up and checked the operation of the Foot Valve.
Then, using my trusty Wet Shop Vac, sucked water in to prime the line (this works very well) and presto! Everything working as it should. Pump fills up the tank in less then 2 minutes.

Then 2 hours later, the renters arrived for the week. Glad I got it working!

The old intake line had a Heater cable in it, so I think this may have been the cause of the problem. Probably all filled up and clogged with debris, thus restricking flow.
Everybody thinks I was a plumber in a past life. LOL.

thanks for your help and suggestions,

Siegfried