Browse Forums Eco Living 1 Aug 08, 2013 12:48 pm I often see water tanks fitted with submersible pumps and my observed two common areas of concern are when... 1. The pump sits directly on the floor of the tank, resulting in the pump vacuuming the tank's floor. 2. The pump sits directly under the tank's top meshed inlet. This generates significant sediment resuspension around the pump when it rains. As per the example in the link below, an owner has had a reasonably new submersible pump replaced and the photos show that the pump sits on the tank's floor and is also sited directly under the infeed pipe. Another photo also indicates with red arrows the pump's very low suction infeed. As per usual, the new pump was fitted exactly the same way as the pump it replaced! http://building-our-first-house.blogspo ... chive.html As an aside, the blog also highlights the lack of information that home owners are given by installers. In this instance, the harvesting system was also fitted with a Rainbank automatic mains water switching device and the owner thought that this was the pump! This is also common. Most home owners are also not advised of their cheaper and neater options in regards to mains water switching devices. My questions are: a. Why are submersible pumps that are used in rainwater tanks designed with very low intakes? Perhaps the fitment of a tall saucer type accessory under the pump would isolate the pump from the sediment layer but do any manufacturers option such an accessory? b. If a submersible pump designed for clean water use is fitted/positioned at the very bottom of a rainwater tank, does it void any of the pump manufacturers warranties? c. Do any manufacturers warn against positioning a submersible pump designed for water tank use directly under the tank's top meshed inlet? d. Are there any ongoing maintenance requirements for water tank submersible pumps and to what degree can a lack of maintenance affect the pump's performance, longevity and warranty? e. What parameters define 'dirty' water and does sediment passing through a pump constitute 'dirty water'? Could any respondents please reference their sources thanks as any verified information may be included in a future magazine article. Any additional relevant information would also be appreciated. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Maintenance Of Water Tank Submersible Pumps 3Aug 23, 2013 1:40 am Hi Bels, I wasn't expecting a reply from a manufacturer but the silence has been poignant. I was nevertheless hoping to hear from people who have battled with the sedimentation problems that tanks present and also from others who have experienced early pump failures, the cause or symptoms and any steps that they may have taken to prevent a re-occurrence. I get a lot of calls from people with all sorts of problems and submersible pumps drawing dirty water is a common area of concern. Strangely enough, only a few have complained of early pump failure. A common theme that I have found is that people are usually sold submersible pumps that are way too powerful (and expensive) for their needs. Out of sight, out of mind I guess. I think that a simple way to isolate a submersible pump from the sediment layer would be to place it in a large saucer type vessel as described in point (a) of my first post but I haven't heard of any installers doing this. Downpipes diverted to an inlet directly above the pump should ideally be extended to a calming inlet and I would be very interested to get feedback from persons who have had this option given to them by an installer/plumber. The calming inlet that I have linked below is on a U.S website. http://www.flxxrainwater.com/products/a ... f_calming/ I am very interested to hear of anyone's experience with early pump failures, their cause, financial impost and if there were any warranty issues. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Maintenance Of Water Tank Submersible Pumps 4Aug 23, 2013 2:15 pm Hi SaveH2O In the water industry I have used 100's of submersible pumps for dirty water applications so I would not expect wear to be a big problem. When I have had to use them to remove cleaner water from a tank where settlement has occured I have used floats to keep the pump at the top of the tank.(sorry no photos) Your idea of a saucer would probably work too. I agree with your idea about calming and the following link shows how to make an effective calming device for less than $20 from components available a local DIY store.:http://www.anewhouse.com.au/2012/11/rainwater-tank-inlet-improvements/ Brian The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Maintenance Of Water Tank Submersible Pumps 5Aug 23, 2013 3:13 pm Hi Brian, Thanks for the feedback. I am wondering as to how a clean water pump is defined. I might send an Email off to a couple of manufacturers. I am surmising that because domestic submersibles are constantly vacuuming their immediate area, any sediment ingestion is in regular small doses, hence the lack of feedback I have had about early failures. Maybe clean water submersibles are made tougher than standard clean water pressure pumps; I don't know. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Maintenance Of Water Tank Submersible Pumps 6Aug 23, 2013 3:39 pm In my experience most submersible pumps are centrifugal pumps with reasonable clearances. The only issues with wear that I have encountered are with cutter pumps used when dealing with water containing fiberous matter. The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Maintenance Of Water Tank Submersible Pumps 7Aug 28, 2013 11:37 am Hi SaveH2O, Wow. There are plenty of details in your post. I will try to give you the best answers from my experience. a) In a tank with fresh rain water there would be very slow increase in sediment over time. Most pumps should be able to cope with this over many years. It is recommended from most installers that a general service on the entire system be done every year to maximise the life of the pump. If it was a dam type situation we always do put the pump inside a plastic container. b) If a service is conducted every year and the pump is not operating in an environment that is causing it to strain there should not be a problem with the warranty. c) I am little confused what you mean. For a submersible pump if you position it at the top of the tank you lose the volume of water in the tank. If you are talking about an externally mounted pump the more suction the pump has to draw the more strain on the pump and it significantly reduces the performance and the life of the pump. d) Please refer to answer b. Basically cleaning out all silt and sediment and test operation of the pump itself. e) Dirty water is basically anything you would not drink. You need to be careful with suspended solids going through the pump as some only have plastic impellers. Some pumps have an open metal impellers which allow for certain size solids to go through. Generally speaking that would not be part of a rain water system. Re: Maintenance Of Water Tank Submersible Pumps 8Aug 31, 2013 2:00 pm Hi 4_Pumps, Greatly appreciate your reply, The article will cover numerous facets of rainwater harvesting best practice and I want to include as much beneficial information as possible as most of the tank installs that I see are sub standard and many have non compliance issues. As I am looking at about 30 sub categories, no one category can use too much space. It will be the first comprehensive article ever done on the subject. I can PM you the pump draft when finished if you are interested. Re my reference to submersibles being placed directly on the floor, if they were placed in a container to isolate them from the sediment layer, the container's thickness might be only 3-4 mm. I have never seen this done though but as you have posted, it is done for other applications. My main observation has been that a tank with a submersible will have less sediment because the way that most submersible pumps are installed ensures that they also vacuum the floor. I have 3 small (designated clean water) submersible pumps that I use for flow testing and each pump has filters. Are you able to post which submersible pumps are the ones most commonly used in urban tanks and whether any have filters? I wouldn't think that cleaning submersible pump filters (if applicable) is something that would be easily done by the homeowner. One thing that I do see a lot is when a submersible pump is fitted directly below the tank's top meshed inlet. I have also seen the resultant dirty water (pumped to a cistern) caused by sediment re-suspension when a tanks fills during heavy rain. My own research has found that the bubbles generated by the volume of falling water that I used didn't travel down more than 200 mm and that sediment re-suspension was caused by toroidal vortices impacting on the sediment layer. I want to do some more tests to replicate bubbles generated by a charged pipe during heavy rain and measure their submergence from different free fall heights. Obviously I don't know what the result of this coming experiment will be but is there a concern when a submersible pump is installed directly under a charged pipe due to a (possible?) potential for air ingress when the tank is at a low level and are you aware of any manufacturers fitting instructions that warn against doing this? I have been unable to find any. Do you have any thoughts about this? Thanks again. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Maintenance Of Water Tank Submersible Pumps 9Sep 01, 2013 1:15 am Hi SaveH2O Just a question to your post, what sort of filter is used on your submersible pump? It is anything like a strainer like used on mechanical services water systems (condensor/chilled/heating)? Re: Maintenance Of Water Tank Submersible Pumps 10Sep 01, 2013 9:07 pm Gunna sound silly but I have never come across a rainwater tank with a submersible pump. Always been external to the tank. Besides noise and getting the last 4 or so inches out of the tank, what's the advantage? Re: Maintenance Of Water Tank Submersible Pumps 11Sep 01, 2013 10:25 pm H20 i will venture a reply as long as you promise that your answer will be one paragraph at most!! Most of these rainwater pumps will handle a degree of sediment, and the simple precaution of an elevated position off the bottom of the tank is essential. @builderforlife Building inspector and passionate about construction When you need an expert to take a look. Re: Maintenance Of Water Tank Submersible Pumps 12Sep 04, 2013 11:10 pm Bels ...what sort of filter is used on your submersible pump? I have 3 small submersibles for flow testing new products, they are not the type you would use in a tank. The one most used is a 90 W PONDMATE fountain pump PM4800FP. There are 3 coarse sponge filters but I took them out as the pump only operates under controlled conditions. From what I have seen, the 'filters' in the larger submersible pumps used in tanks are just perforated metal mesh of varying apertures. E1109 I have never come across a rainwater tank with a submersible pump. Always been external to the tank. Besides noise and getting the last 4 or so inches out of the tank, what's the advantage? The problem is that they do draw the worst quality water when they are just plonked on the floor but an external pressure pump will also do that when the tank's draw valve that supplies the pump is fitted very close to the bottom of the tank. The advantages are noise reduction and less outside area needed for the pump and cover. They should probably be used more often than they are. builderforlife Most of these rainwater pumps will handle a degree of sediment, and the simple precaution of an elevated position off the bottom of the tank is essential. Agree. Davey and Onga are two popular pumps. The following is off their fitting instructions: DAVEY: Pump should always be installed so that it will be clear of settled silt or debris. Don’t pump abrasive materials. Sand and grit in the water being pumped will accelerate wear, causing shortened pump life. Your Davey Two Year Guarantee naturally does not cover.....failure to properly follow the provided installation and operating instructions..... ONGA: TankBuddy is designed to be used with clean water in a residential application. Lower the pump onto a hard level surface that is elevated from the base of the tank. This is to keep the pump inlet above sediments in the bottom of the tank. This product is to be installed and operated in accordance with the instructions provided. This warranty will not apply if it is used in a manner other than in accordance with the instructions. Couldn't fit all the above into one paragraph...sorry! 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Maintenance Of Water Tank Submersible Pumps 13Sep 05, 2013 6:48 am I've had issues with my underground tank - but it seems to work OK. Question - are we talking above ground tanks here - or underground ? Or doesn't this matter ? The pump does seem to go straight down with a cistern like device to tell the gauge how much water is available before the mains cuts in. My house drains all have filters and the water looks good enough to drink - ie you can see the bottom of the tank - even though it is dark (and eerie). As it is yet to get to the "empty" stage I haven't experienced it cutting to mains yet. Is there a way of telling when this happens ? My tank tap appears to actually have the best pressure in the house - leaves the mains water pressure for dead. It was tested etc to ensure no leakage back to the mains water. But looks very good. Re: Maintenance Of Water Tank Submersible Pumps 14Sep 05, 2013 11:04 am Question - are we talking above ground tanks here - or underground ? Or doesn't this matter ? DOESN'T MATTER The pump does seem to go straight down with a cistern like device to tell the gauge how much water is available before the mains cuts in. FAIRLY STANDARD My house drains all have filters and the water looks good enough to drink - ie you can see the bottom of the tank - even though it is dark (and eerie). THE WATER NEARLY ALWAYS LOOK GOOD FROM THE TOP BECAUSE ALL THE SMALL PARTICLES QUICKLY DROP TO THE BOTTOM (see: http://www.anewhouse.com.au/2012/11/und ... r-quality/) THE PROBLEM WITH SUBMERSIBLES AS THEY SIT ON THE BOTTOM IS THEY TEND TO 'HOOVER' THESE PARTICLES DIRECT TO YOUR TAPS. As it is yet to get to the "empty" stage I haven't experienced it cutting to mains yet. Is there a way of telling when this happens ? IN YOUR CASE THE PRESSURE WILL PROBABLY DROP The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Maintenance Of Water Tank Submersible Pumps 15Sep 05, 2013 1:20 pm Hi guys, I hope that this answers your questions: - What type of submersible pumps: When using a pump in a rainwater tank situation you would need to use a pressure pump (http://www.4pumps.com.au/categories/pressure-pumps/). These are available in both an externally mounted or submersible pump options (http://www.4pumps.com.au/categories/submersible-pumps/). This will insure you have great pressure through out a dwelling. - What filter to use on submersible pump: There is no real reason to use filters on submersible pumps if the installation is done correctly. The rainwater should have a rain head (remove leaves), first flush diverter (removes sediment), leaf strainer (removes smaller particles) and mosquito net on the overflow. The water should be clean and free from impurities when it is inside the tank. Obviously there will be some sediment that goes through but it will be largely reduced with a first flush diverter. Also putting a filter on the suction side of a pump can reduce performance and life. - Why use submersible pump: There can be several situations where a submersible pump would be preferred. For example to reduce noise or where there would be a large suction lift on an externally mounted pump. Some of our customers have requested for a "silent" pump if the pump is near their bedroom and keeping them up in night if somebody goes to the bathroom or the tap is leaking. When there is a large suction lift on an externally mounted pump, a submersible pump might be preferred to reduce the strain on pump to increase performance, increase the life of the pump or potentially allowing you to use a smaller pump and reduce the electricity consumption. - Float switch or press controller: In a rainwater tank system you would not use a float switch. If the tank was full the pump will be running all the time even if nobody was using any water. This would use excess electricity as well as eventually burning a pump out. What is recommended is a press controller (http://www.4pumps.com.au/categories/add ... ontroller/). This would sense when water is being used and switch a pump on accordingly. Again when water is no longer needed if would turn the pump off. - Cross connection controlling devices/ water switch (http://www.4pumps.com.au/categories/add ... ontroller/): These devices allow you to use both tank and town water automatically. It senses the level of water in a tank and will use that first. If the tank runs dry it will switch over to town water. There is a new product which is coming out we believe in the next month or so. It will make it easy for people to install themselves and will be much cheaper than current options in the market. We will keep you updated when the Wiwo is available. I have addded some links if you want to see what I am referring to Re: Maintenance Of Water Tank Submersible Pumps 16Sep 05, 2013 2:38 pm What water depth will a common submersible pump usually reduce the tank level to? I realise that this is a 'piece of string' question as the generated vortex is dependent on the rate of suction but I have concerns when I see submersible pumps installed directly under the tank's top meshed inlet. EDIT 6/03/2014 Many pump manufacturers recommend that an external pressure pump maintains a 300 mm head above the tank's outlet valve that supplies the pump. If the water level drops too low and a vortex is formed, the pressure switch will detect a pressure drop and stop the pump. The 'unusable' water can be expressed as a % of the tank's storage capacity. A squat tank therefore has a greater % of water that the pump cannot draw. This is the reason that many tanks are fitted with very low pump draw outlets. The disadvantage is that the outlet then sits near the sediment layer and will draw the worst quality water. Submersible pumps are quiet and efficient but they draw the worst quality water from the bottom of the tank. Many submersibles are also designed to draw water through meshed holes around the bottom of the pump. The meshed holes cover a larger intake area than a tank outlet that supplies an external pump. Multiple small meshed intake holes also act as vortex reducers, allowing more water to be used. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Maintenance Of Water Tank Submersible Pumps 17Sep 05, 2013 2:44 pm No problem at all. Love to help. It depends on the particular submersible pump. I would think most will suck down to 4" inches. Putting the pump under the leaf strainer means that you have an access to it. Otherwise you will need to get into the tank for maintenance. There is a whole bunch of regulations surrounding confined spaces. With all the previsions mentioned above it will not cause any problems. Re: Maintenance Of Water Tank Submersible Pumps 18Sep 05, 2013 2:56 pm Thanks for that. My concern is in regards to the pump's possible ingestion of bubbles generated by falling water if the water level is low and the submersible pump is sitting directly under the tank's top inlet. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Maintenance Of Water Tank Submersible Pumps 19Sep 06, 2013 9:35 am Hi SaveH2O, Realistically this will occur .1 % of the time. That combined with velocity of the water moving through the pump should prevent any damage to the pump. After years of experience we are yet to see this cause and issue. If it worries you just move the pump 300 mm to the side. Cavitation only causes damage to a pump over a long period of time. So these bubbles happening around once a year should be fine. 18 90470 From what I know about water tanks (I've been working with a client on them for a few years now) is this - The concrete can last a lifetime if they don't crack for some… 2 10625 If you can calculate the reasonable charged head from let's say 100mm below the gutter to the top of where the vertical riser's horizontal discharge pipe will be, that… 11 17530 |