i have been reading renew for a while now and really like how it looks at all aspects of renewable living.
i was reading issue 115, on page 16 don batson has written about how he installed a water tank and had it fitted with a 260lt pressure tank. This was to avoid the pump starting every time a tap was turned on as this provides about 100 to 130lts of water before the pump starts. i feel this is a really good idea to save power and increase pump life.
i was lookig on ebay for pressure tanks to use and found a couple. this got me thinking of what else could be used and i thought of an old beer keg they are around 50lt and meade from stainless so wont rust.
i was just wondering if you need a rubber bladder in them? some pressure tanks have them and others dont?
pressure tank for rainwater pump(49 posts) (21 voices)
hi allPosted Sunday 22 May 2011 @ 2:04:20 am from IP #
I think the complexity of making your own pressure tank might be greater than you imagine. You would need to somehow be sure that the internal bladder worked at the right pressure range and could hold a good water tight seal. A cheap one off ebay would probably be the easiest option.
Renew is a good read.Posted Sunday 22 May 2011 @ 10:21:10 am from IP #
A keg can be used but unfortumately the air will slowly disolve into the water and stop it working (that is the function of the blader to keep the air and water seperate)
I have used a non blader tank before but it needs to be either drained regualy to let air in or a valve on a tee to allow a tyre pump to pump in air.
The bladder sure does make it easier
JoePosted Sunday 22 May 2011 @ 10:43:20 am from IP #
I appreciate the idea of the pressure tank to extend pump life by fewer turn ons of the pump, but how does it save power (or energy really) ? I don't think any turn on surges are significant if the pump runs for 30 sec or so each time, so if the overall effect is to pump the same amount of water to the same pressure, how is energy saved ?Posted Sunday 22 May 2011 @ 1:52:18 pm from IP #
Every pump start uses around 5 to 10 times the run energy for a few seconds.
Every pump start lessons the motor life.
If you can a tank on the hill only running on off peak power would be ideal the gravity all day and top up tank every night on cheap power and a long pump life is the ideal
The other great advantage of a day tank is you have water when the power is off, great for out of town rural supplies which often fail in windy conditions, bush fires etc
JoePosted Monday 23 May 2011 @ 12:33:10 am from IP #
Also, running pumps from solar means that excessive pump starts can cause probs for other appliances, as a starting pump can suck up all available inverter capacity for a second or two, so it makes a lot of sense to have as few pump starts as possible...Posted Monday 23 May 2011 @ 1:50:36 am from IP #
how dose the bladder work? what is it used for?
is it that the air in the bladder compresses more than water? and then as the water pressuer relases its taken up by the expanding air?
cheers andrewPosted Monday 23 May 2011 @ 6:35:56 am from IP #
"so if the overall effect is to pump the same amount of water to the same pressure, how is energy saved "
It might be the same amount of water but it is pumped over a longer period of time (lower flow rate) and a slightly higher pressure (which is dissipated by the flow restricting tap or toilet cistern).
Centrifugal pumps have a point of optimum efficiency for water flow rate vs the pressure (head) of the water. Away from that point the efficiency decreases - a little away from that point the efficiency decreases a little, a lot away the efficiency decrease a lot. So if a pump is operating at a low flow rate (lower than optimum) the efficiency of the pump is also low. A pressure tank (properly matched to the pump) will keep the pump running at closer to it maximum efficiency.
E.g. - http://www.gouldspumps.com/cpf_0009.html - Refer figure 8 at bottom of the page. Bigger pump but same principle. For 13 inch impeller size max efficiency is something over 60% at around 160 ft head and 300 gallons per minute flow rate. At 100 gallons per minute the efficiency drops to something below 40%. Lower the flow rate more and even lower efficiency.Posted Monday 23 May 2011 @ 11:57:27 am from IP #
A pressure tank also 'softens' the feed pressure when connecting a rainwater tank pump to a washing machine. A lot of pumps can cause 'hammer' when directly connected, particularly when feeding through copper pipe.Posted Monday 23 May 2011 @ 3:12:45 pm from IP #
Hi Diver - I find that our system does have a bit of water hammer when the washing machine is using rainwater. I have a pressure controlled grundfos pump - do you know if it is compatible with a pressure tank or do I need to go to a different control system to make it work. I keep getting conflicting answers from retailers and suppliers.Posted Tuesday 24 May 2011 @ 2:54:12 am from IP #
If it has a pressure switch then it can be used with a tank, the switch just keeps the pressure in the system between two points, the pump turn-on and turn-off points. Worst case, you buy a tank and the switch acts screwy and you have to replace the switch, but that's not a prob, there's plenty available at low cost.
I am amazed that any domestic systems are installed without a decent pressure tank, they have many advantages and no disadvantages and are cheap, so why wouldn't you install one?Posted Tuesday 24 May 2011 @ 3:19:13 am from IP #
I guess there is just a lack of knowledge about their purpose and benefits. I consider myself reasonably well informed on domestic environmental projects but am in the dark on this topic.
Also - not a single one of the plumbers I spoke to during the evaluation phase of my rainwater tanks mentioned a pressure tank. I would say they also lack the knowledge to advise people sensibly. I also noticed they generally put very little thought into pump selection and were advising me to go with a pump far larger than I ended up with after consulting with a friendly water engineer. I think they just want a simple one-size fits all fix rather than an optimal, efficient installation.Posted Tuesday 24 May 2011 @ 3:34:46 am from IP #
I think Lance has answered your query.
My understanding of modern washing machines is that they have a fairly high pressure requirement and fast acting solenoids. I also understand that water hammer can also adversely effect the pump whereas the pressure tank's bladder absorbs any hydraulic pressure waves. As to the effect water hammer may have on the washing machine...I don't know. With less pump wear and tear, lower energy use and other benefits, larger pressure tanks are well worth it.
I am about to connect my main tank to my (electric) HWS and my current small pressure tank will be replaced by a much larger one. I presently turn the pump off and gravity feed to the toilet but I wont be able to do that once I connect to the HWS. Even so, it will probably only start up once a day to recharge the new pressure tank, all the while running at its most efficient in the pump's sweet spot. Cool!
The lack of knowledge by the 'experts' that you mentioned is a constant frustration to me here in Victoria. I see hundreds of tank installations every year and I have estimated that about 40% are not compliant and at least 95% are sub standard. In the vast majority of cases, householders have also paid too much and the incompetence of many installers and tank retailers is now seeing an increasing number of pumps failing due to the tank draw off valve been fitted too low and ingesting sludge, tanks overflowing during the more frequent and intense rain events and infeed pipes silting up.
Re pumps, a lot of people get a bigger pump so they can water the garden with adequate pressure. Buying an 18 mm hose and connecting it to a short length of 12 mm hose so that garden accessories can be used will substantially reduce dynamic head loss.Posted Tuesday 24 May 2011 @ 3:24:36 pm from IP #
Just ordered a 100L pressure tank from ebay , so l'll see how that goes ..........l'm running it with a Grunfos CH series constant pressure pump , l was told by Grunfos to run 180 kpa air pressure , so i'll see how that goes for a start.
Somthing l've noticed is the pressure tank has a restrictor/filter in the base of the outlet , that'll be ok for refilling but l thought it'd be better for more a more open outlet for fast flow situations .....maybe it's to regulate flow and let the pump kick in high flow situations ?
Cheers KenPosted Sunday 5 Jun 2011 @ 4:31:25 am from IP #
Just had a rain water tank installed. This was connected up to the washing machine. Problem is that when the bowl is full and has reached the water level, the water from the rain water tank continues to flow in (hence, lots of water to clean up) I switched back to the mains to make sure that it was not the machine (Simpson, 19 years old!!) but sadly, no. Since connecting this to the rain water tank, I have had this problem. Same as if I lift up the washing machine lid, the water continues to flow and does not stop. The plumber that I used says he cannot explain this. The pump that has been fitted is a 300W 2 Tap Auto Pressure Pump (100ka) Any suggestions gratefully accepted!!Posted Sunday 12 Jun 2011 @ 9:54:28 am from IP #
Thats weird........the washing maching should'nt care what water is entering it as they shut the water flow off at certain levels...........Posted Thursday 16 Jun 2011 @ 10:32:58 am from IP #
I remember this problem when I used a header tank years ago. Its not a level sensor issue it's the solenoid. The return spring in the solenoid initiates the turn off sequence but relies on the incoming water pressure to complete the shutoff. At the time I changed the valves to a different type. Unfortunatly most dishwashers and washing machines use these cheap valves nowadays. All I can suggest without modifying the machine is a pump with a higher pressure. It may be worth checking that any restricting washer has been removed and temporily replacing the water hose as some have a restricted diameter one end this might be enough...Good luckPosted Friday 17 Jun 2011 @ 1:22:57 am from IP #
We run a washing machine (and dishwasher sinse 1980)on tank water with a pressure of <150 kPa, the only problem we find is some times the solenoid sticks part open with a bit of debris under the disc, you should have a strainer on the inlet of the solenoid check its condition and clean the solenoid (you might need a washing machine mechanic to do this if your not confident to do it your self)Posted Friday 17 Jun 2011 @ 4:06:32 am from IP #
I sell both cheap and quality pressure pumps with either the old fashioned pressure switch with pressure tank and the newer constant pressure/flow electronic controls. With the newer electronic control pumps, I always recommend a pressure tank for domestic applications and the capacity will depend on how large the family or how old the kids are. With single phase pumps it is mostly the start capacitor that blows up first, then the user keeps trying to start it until they burn out the motor, a quality motor will last for many many years if the supply voltage remains within its stated operating range.Posted Friday 17 Jun 2011 @ 6:22:15 am from IP #
@ unevano, have you got a web site mate?Posted Saturday 18 Jun 2011 @ 10:46:58 pm from IP #
We also read the article and we are looking at connecting our tank to our house and were looking at a pump connected to a pressure tank, as we will be running off-grid solar, we dont want the pump running constantly when we are having a shower, or when we go to the toilet during the night.
We went to get a few quotes and one place said it wouldnt be a problem, the next place were reluctant to give us a quote for a pump and pressure tank, even though we explained the situation, and they were leading more towards a pump with a pressure system incorporated.
Is this the way to go, or should we stick with a pump and pressure tank.Posted Sunday 19 Jun 2011 @ 10:27:36 am from IP #
Stick with the tank, the various pressure control systems are no replacement. As with most things, the KISS principle applies. I would never install a complex control system when a steel tank can do the same job with less chance of failure...Posted Sunday 19 Jun 2011 @ 11:28:09 am from IP #
l finally hooked up the 100L pressure tank, and am very happy with the results
We get around 25Ltrs out of it before the pump kicks in , and showers etc work well , with no noticable fluctuations in pressure So far so good
The only downside was the ebay tank turned up with a couple of small dents in it.......l had taken out extra insurance on it so that helped , but to get a full refund it had to be sent back........at my cost ( was'nt happy ) so ill probably take the 50 per cent refund and keep the unit ........so a word of warning , make sure you specify for the unit to be packed properly, and also take out the insurance as there's no comeback otherwisePosted Thursday 23 Jun 2011 @ 7:46:36 pm from IP #
this website has a good explanation and diagrams of how a bladder filled pressure tank works - the relevant example is about 2/3 of the way down the page and is called
Using a bladder to feed Homes and buildings
for low pressure or emergency water storage.
Using a pressure bladder to allow pumps to turn off.Posted Thursday 29 Sep 2011 @ 12:15:16 am from IP #
Does anyone know if there is a limit to the size of tank you can use or is there a formula to determine the tank size based on the pump?
this is all I have found so far -> http://www.cheapapumps.com.au/wellmate_pressure_tanks.html
"As a basis guide you can use the following:
Up to 1hp motor (say 30-40LPM) Use a 60-75L tank
Up to 1.5hp motor (60LPM) I would use a minimum of 75L tank
2hp motor, use a 112L tank
3hp motor, use a 180L tank
4hp motor use any size bigger than 180L "
I have also discovered that the draw off amount is about 1/3 the volume of the tank and then the pump kicks in (at least that's what the table looks like on that page).
Can anyone comment? I'm looking at using an Onga SMHP55 or SMHP75 but unclear on a tank.Posted Saturday 17 Dec 2011 @ 10:21:20 am from IP #
Unfortunately, tank prices seem to have risen in the last few years, the other supplier I know of is http://pumpwarehouse.com.au/category8_1.htm who have onga tanks, but similar prices, a slightly cheaper 450 litre unit is at http://www.rainwatertankpumps.com.au/prod78.htm.
I know Collyn Rivers up in Broome added a large tank to his system, which only cycles the pump once a day. He found it cheaper to import a tank from the US than buy one in Oz, how crazy is that.
Or, if the budget is really tight, you could install one or more of these: http://www.ebay.com.au/itm/170739964902 but just make sure they are well protected from weather as they are prone to rust eventually, although the one I had, despite being in the weather, was looking pretty good after the first year.Posted Sunday 18 Dec 2011 @ 12:19:53 am from IP #
Thanks Lance. Feels odd to be looking at more than double the price of a pump for a tank but then again there are advantages that are hard to quantify like having water pressure during a blackout I'll see what size I can fit out of the weather. Thanks again.Posted Sunday 18 Dec 2011 @ 3:32:35 am from IP #
Or, if the budget is really tight, you could install one or more of these: http://www.ebay.com.au/itm/170739964902 but just make sure they are well protected from weather as they are prone to rust eventually, although the one I had, despite being in the weather, was looking pretty good after the first year.
hi Lance, is this one easy to install? any pitfalls?Posted Sunday 26 Feb 2012 @ 1:09:15 am from IP #
I had the 24 litre version of that and like all tanks, it's just a steel tank with a bladder, you just use the appropriate pipe fittings to hook it to the output of the water pump. There's nothing to it really, anyone can do it, just make sure the fittings are sealed properly and that the tank is pumped to the correct pressure (can take a bit of experimentation to find the ideal pressure for your pump's pressure switch range).Posted Monday 27 Feb 2012 @ 5:27:01 am from IP #
Finally found a supplier of pressure tanks -> up to 10,000 litres in fact - WOW !!!
So here is the link if anyone is interested http://globalwatersolutions.org/index.php?page=potable-water
I have requested information as to whether they they sell ot individuals or not- I'll update once I have received the information.Posted Saturday 17 Mar 2012 @ 10:34:00 pm from IP #
You must log in to post.