Pump and tank advice, please, borehole supply in the UK

Users who are viewing this thread

Reach4

Well-Known Member
Messages
38,798
Reaction score
4,412
Points
113
Location
IL
I am not able to use the pellets myself, because my steel casing is 4 inches ID and my pump is 3.7 to 3.75 OD. If I have the pump pulled in the future, I would look to get pellets dropped before the pump. With your pump and casing sizes, you could easily clear pellets even with the pump in place.

I suggest this search engine search as a starting point: well sanitizer hypochlorite pellets shock
which will turn up pellets made for the purpose, or replace the z to see if you get more local hits.

The pellets made for the purpose seem to be about 5/16 to 3/8 inch diameter (~ 9 mm). There is some question about whether pool pellets would contain something not suitable for potable water. Plus, at least some of the chlorine pellets for pools are meant to dissolve very slowly -- a week or more. I guess you could experiment with the dissolve time.
 

Jeremy Harris

Member
Messages
47
Reaction score
10
Points
8
Location
United Kingdom
Thanks that's very useful, as I've checked the big tablets I have and they are exactly as you describe. They are intended to dissolve very, very slowly over many days and they can leave chloramines behind in the water. I'd hunted around and found a place locally that sells the pellets you describe, so will use some of them before I drop the pump back in, just to be dead sure they get to the bottom. Now the well is nice and clean I want to try and keep it that way!

The good news is that the drilling company boss has been on the phone as soon as he had my email with the video link and is coming over to see me. I get the feeling that he isn't doubting anything I've said or done and is keen to come to an amicable arrangement about me having paid him for a 70m well when he's delivered a 53m well! With luck we'll reach an agreement and will both have learned something in the process, even if his learning may well hit him hard in his pocket....................
 

Jeremy Harris

Member
Messages
47
Reaction score
10
Points
8
Location
United Kingdom
One of the consequences of pumping sand seems to have been that the Grundfos SQ1-65 pump no longer wants to pump above about 5 bar (~72 psi). I was operating this system with a turn off pressure of 5 bar and a turn on pressure of 4 bar (~58 psi) with two 300 litre bladder-type pressure tanks pre-charged to 2.5 bar (~36 psi). This combination worked really well to give me enough flow rate and volume to backwash the iron filter despite me having a flow restrictor valve fitted in the pump line to keep the pump flow rate down below 10 litres/minute (~2.6 US gallons/minute). It also gave a good back up of stored water should the pump go off line, as it has been during the recent work (luckily I'm still building the house so the water is only for the toilet, hand washing and making cups of tea).

There's going to be a dispute over the warranty repair of the Grundfos pump, I know, but the drilling company that supplied it told me, in writing, to run it continuously to waste for two weeks to clear the sand from the well. My view is that I shouldn't pay for the repairs, as it seems likely that they are due to wear caused by pumping all that sand that I finally got out last week, but in the meantime I need a pump to run the house for a while until the Grindfos gets fixed, just a cheap back up pump that I can keep as a spare.

There's a Polish company I've bought other stuff from who are really good value here, and the products look to be well-engineered (I worked with some Southern Polish engineers years ago and found they were damned good, so I tend to trust Polish made stuff).

I was amazed to find that this Polish company (Dambat) manufactured a couple of 3" diameter stainless steel borehole pumps (they even make a 2" diameter pump) What was more amazing was the price. I don't know the price of pumps in the USA, but here we pay the equivalent of at least $500 for a cheap, no-name (probably Chinese-made) pump, up to way over the equivalent of $1000 for a decent brand name pump (the Grundfos I have was around $1000).

The Polish pumps were amazingly cheap, they do a small 20 litre/minute (~5.2 US gal/min) 7.5 bar 3" pump for just about $105 (delivered) or a more powerful (1hp) 11 bar, 40l/min pump for around $170 delivered.

As a spare pump for emergency use that I could use whilst the Grundfos was being fixed, and to keep as an emergency spare the larger of the two looked to be a really terrific bargain. I trust the company, having bought a nicely made pressure set surface pump and pressure tank from them (which were also very good value) so I didn't feel it was taking a big risk to buy one of their well pumps as a spare.

I've looked at the pump curve and spec and it seems fine, at 10 litres/min the bigger of the two 3" pumps they sell can still deliver 8.8 bar (~127 psi), so even allowing for my resting water level in the well (standing head effectively) and the pipe losses from the pump to the pump shed, I should still be able to get around 7.5 bar or more at the pump shed. There is some limited info on these pumps, with curves, on their web site, here: http://www.dambat.com/sqibo-deep-well-pump.html

My question is this. Having looked at the pump, I've found it uses a screw displacement pumping method, rather than staged impellers (usefully they sell the screws and stators as spares pretty cheaply, as in a bit over $50 delivered: http://www.ebay.co.uk/itm/spare-hydraulic-kit-for-IBO-3-SQIBO-0-75-borehole-pump-/171820480373 ). Now I know nothing about positive displacement pumps like this, except what I've ready on this Wikipedia entry: https://en.wikipedia.org/wiki/Progressive_cavity_pump

So, how is a pump like this going to behave when fitted with the flow restrictor I'm pretty sure I still need? My first thoughts are that, from the pump curve, the pump side pressure will rise to around 8.8 bar with the restrictor in place, and that there must be some leakage back past the rubber stator moulding in the pump that means the pump isn't a "true" displacement pump, but has a progressive leak back past the screw as the pressure increases. My second thought is that it probably needs a check valve at the well head (no problem to fit) as the top of the rotor shaft and the stator opening can be seen just below the 1" BSP pipe connection and this type of pump probably doesn't have, or need, a foot valve. The down side on it being Polish is that the instructions are not exactly clear!

If anyone has any knowledge of positive displacement screw-type pumps and could confirm or deny what I've assumed above I would, as ever, be very grateful.

(BTW, they sell these pumps in the UK from their UK warehouse in London, via Ebay of all places. Their Ebay store is stores.ebay.co.uk/division303pump in the UK, if anyone is interested at looking at their stuff. I hope mentioning this isn't breaking forum rules - I just thought it might be of interest to see what's available from other parts of the world).
 
Last edited:

Texas Wellman

In the Trades
Messages
1,035
Reaction score
59
Points
48
Location
SE Texas-Coastal
Eh....progressive cavity pumps are normally used for very special purposes. Make sure you have a relief valve installed-it will build high head.

For the money it might be worth a shot.
 

Reach4

Well-Known Member
Messages
38,798
Reaction score
4,412
Points
113
Location
IL
The Polish pumps were amazingly cheap, they do a small 20 litre/minute (~5.2 US gal/min) 7.5 bar 3" pump for just about $105 (delivered) or a more powerful (1hp) 11 bar, 40l/min pump for around $170 delivered.

As a spare pump for emergency use that I could use whilst the Grundfos was being fixed, and to keep as an emergency spare the larger of the two looked to be a really terrific bargain. I trust the company, having bought a nicely made pressure set surface pump and pressure tank from them (which were also very good value) so I didn't feel it was taking a big risk to buy one of their well pumps as a spare.
Why would you not opt for the smaller pump? Getting the bigger pump with a flow restrictor does not seem right.

Your static water level is high -- about 11 ft. I wonder if it would make sense to set your pump higher so that it is not going to suck sand.
 
Last edited:

Jeremy Harris

Member
Messages
47
Reaction score
10
Points
8
Location
United Kingdom
Very good questions!. I guess I went for the higher rate pump on the basis that "bigger is better", even though I know that's not a good argument. Also, at the time I bought this pump I didn't notice the fact that both these 3" pumps were positive displacement "progressive cavity pumps". TBH, I'd never ever heard of a "progressive cavity pump" so assumed these things were multi-stage centrifugal pumps, like the majority of similar looking stainless well pumps. It was only when the pump arrived and I went to fit the 1" top fitting that I saw the odd looking offset outlet hole and the tip of the pump screw shaft and if made me wonder. Ten minutes of internet investigation showed exactly what I'd bought. I've still no idea how they make these so cheaply, especially as the quality looks good - far better than a lot of the Chinese made crap around. Originally the drillers set the pump at 45m (around 148ft) down, but when I had really bad sand problems and found that when pumping continuously at around 30 litres/min (around 7.8 US gals/min) for days on end the rest water level would pull down to around 13m (around 43 feet) I lifted the pump to 25 metres (around 82 feet) which is where I've had it since. It may be I could lift it a bit more, I just wanted to make sure it had a pretty good margin below the lowest water level I'd seen.

At 25m the pump is still 28m off the bottom of the well, a fair old distance. The problem is the very fine sand has a very long settling time (several hours) so once it's being pulled in through the slotted liner section it's going to get sucked into the pump, even if the pump is as high as it can go. I expect this to get better as the sand packs up around the glass media pack around the well liner, giving better filtration, but for now this is pretty much what I have to live with

I reckon the very cheap, smaller pump, would have been a better match, but I do still have an 8 bar pressure relief valve, so I can fit that to stop the bigger pump from putting more than a 3 bar differential across my home-made venturi/air/ozone injector. In many ways, having a higher pressure differential across the venturi is a good thing, as it means I'll get more consistent suction and won't need so much pressure at the air inlet port. I'll still need air/ozone pressure under some conditions, and having seen how very effective ozone injection is at getting iron and manganese out of the water, and helping to drive out the hydrogen sulphide, I'm keen to make this as effective as possible by blowing ozone/air in there if the pressure differential isn't enough to allow it to suck at atmospheric pressure.

The flow limiter valve is a low rate, 10 litres/minute, or around 2.6 US gals/min, and is set that low to limit very fine sand being picked up. It may well be that now I've cleaned the well out, and proved it to be clean, I can increase the rate, but I'd like to do this in stages, so if there is a problem I have a reasonable chance of finding where the problem came from.

Part of me likes that getting all this stuff to work is like a big lab experiment, where you learn loads of things when things go wrong, but the bottom line is I need to have a reliable water supply for our new home and cannot play around with it as some giant experiment for ever.

Thanks as always for the help and encouragement, it is very much appreciated. You guys know so much more than the few UK firms doing this that it's just amazing to have your help here,
 
Last edited:

Jeremy Harris

Member
Messages
47
Reaction score
10
Points
8
Location
United Kingdom
Just to say I resolved the potential dispute with the drillers amicably, and was compensated for the shorter depth drilled than paid for (with a good explanation as to how the error happened), the Grundfos pump is getting fixed by the drilling company, no matter what Grundfos have to say about the warranty and sand, and as a stop-gap I lowered the Polish pump down the hole yesterday.

I can say for sure that the spec curves for this Polish pump were VERY conservative! They understate the head it will pump to at a given flow rate by a fair margin, and when I first tried it with a 8 litre/minute flow restrictor I drove the needle on my 12 bar pump-side gauge right around the the wrong side of the zero stop, so probably around 14 bar! I switched off as soon as this happened, and swapped out the flow restrictor for a 12 litres/minute one (about the max I can draw without drawing in very fine sand).

This worked fine. I have a pretty constant 10.5 bar on the pump side all the time the pump is running and up to 5.2 bar on the house side. This is still way over the pump spec, as the curve for the 750W SQ IBO pump shows that the pump should deliver about 8.5 bar at 12/litres/minute), but the system is working OK. I have my air/ozone injector temporarily hooked up and should get that properly installed today (if the rain eases off) and the new well head with it's stainless flange and decent seals I've installed looks a lot neater than the old arrangement with the loose cover.

I have a pressure relief valve I think I may just fit on the pump side, as the pressure is a bit on the high side, but the pipe is all certified for 16 bar minimum so 10.5 bar shouldn't be a problem.

When I get the Grundfos pump back I'll just swap it over and keep the cheap Polish pump as a spare, just in case we get another problem. For now it looks like my well problems are resolved, thanks in part to some of the helpful advice and reassurance I've had from members of this forum.

From a few thousand miles away, I'd like to thank you all for your help and advice.

Jeremy
 

Valveman

Cary Austin
Staff member
Messages
14,599
Reaction score
1,296
Points
113
Location
Lubbock, Texas
Website
cyclestopvalves.com
Yeah those Polish pumps look like they are positive displacement. That means they don't like to be restricted with any kind of valve. The more they are restricted, the higher the pressure and the higher the amperage will go. I thought I was mistaken about this when I looked at the pump curves you supplied. But after hearing the pressure gets much higher when restricted, I see the curves are wrong.
 

Jeremy Harris

Member
Messages
47
Reaction score
10
Points
8
Location
United Kingdom
I can tell you I ran pretty fast from the well pit to the pump house to turn the pump off when I first saw the 12 bar pump-side gauge bouncing off the back side of the zero pressure stop, when I had the 8 litre/minute restrictor fitted. It was like one of those Scotty moments from Star Trek, the ones when Scotty always says something like "she's going blow any second, Captain!!!".

It seems happy enough delivering at 12 litre/minute and 10.5 bar though, so I reckon it'll survive the few weeks until I get the Grundfos back in service.

The curves are obviously way wrong at the low flow rate end, where the pressure rise a heck of a lot more than the curves show. I reckon deadheading this pump would probably burst the 16 bar rated pipe I have.......................
 
Last edited:

Valveman

Cary Austin
Staff member
Messages
14,599
Reaction score
1,296
Points
113
Location
Lubbock, Texas
Website
cyclestopvalves.com
Most curves for positive displacement pumps just keep climbing until the motor overloads. If the motor is strong enough to keep spinning the pump, the pressure just keeps going up. Turn it off quick or you will be saying, "she's coming apart at the seams Captain".
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks