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Nick

Pushing v pulling water

We have very low water pressure, as we are not on the mains. All our hot water is pumped to baths and showers. The pumps are at the outlet end, rather than by the hot water tank.

Am I right in thinking they'd probably perform much better near the tank, rather than several metres away, and moving them is a better idea than replacing with a bigger pump?

Seems common sense, but wanted to check.
vegplot

It will depend on the pump and how it's designed. If you already have a pump check with the manufacturer. We use a pump for the shower and locate it close to the tank but I can't recall whether that's preference or a requirement.
dpack

what he said but a bigger better pump is often the thing that works best as the greatest limiting factors are the pipe diameter ,number of bends ,vertical rise and length.
Nick

Given the outlet height from the hot water tank, the bath taps are below it. However, it's probably 10m away, and there's a lot of bends I cannot change under and around the bath. It takes about 40 minutes to fill the bath.
dpack

that seems very slow ,has it always been that slow or has it got slower?
sean

Maybe it's a very big bath.
vegplot

Assuming you can do little to modify the system except add a pump then your biggest consideration is where to site the pump that gives you best access to fit the pump.

We have a hot water tank lower than the outlet of the shower head in the room next to the bathroom. We fitted a pump next to the tank in the hot water supply only (we have mains pressure) but I presume you want to boost both hot and cold from the same pump? If so just make sure you buy the right pump.

We got our from B&Q for around 100 (ish) and it's worked well but doesn't like really hot water (over 70C) which we sometimes get from the stove.
Falstaff

You can't "pull" water - all you can do is to reduce the pressure at your end of the pipe and wait for the air pressure at the tank end to "push " it along to you.

The maximum pressure you can ever get is about 14 lb/sq in, bends branches and frictional forces will reduce your hydraulic pressure.

[Edited to say the maximum height you can achieve using a "pull" pump is just shy of 30 feet - if you lift the water 15 feet you will lose half your pressure. ]

You CAN "Push" water and you can wang it up to tonnes /sq in or until your pipes just burst.

Whether you can do that with the same pumps will depend on the pumps - but if you look at domestic central heating or a power shower, the pumps are always near the tank.

I'd say go for it ! At the end of the process you may need to buy another pump, but I rather think you'll be ok - And you can't wait 40 minutes for a bath every time !

[Edit 2 to say - I'd be supicious that your pipes are furring up - are you in a hard water area ?]
dpack

i was considering fur but i think nick is over sandstone which should be ok.

a bigger pump at the tank end is possibly the best option if there is room and a power supply for it.iirc bits of the house were built before the ice age and it has a variety of levels ,solid bits etc etc and finding room for new pumps,pipes and wires might be rather tricky
Nick

There's actually lots of room around the hot water tank for pump, access and power.

We are prone to limescale, as we're on a well, not mains. Kettles do not live long.

It is a very big bath, but even so...

And it's always been about this bad, and I have to replace the pump every 3-4 years as they die/leak. They get furred up, too, which doesn't help. This one is towards the end of its life, so am probably going to have to do something, either way.
Nick

Eta. I can wait 40 minutes, as it goes. Alarm goes off at 6.45, she gets up, puts bath on, makes packed lunches, wakes son, pokes horses about, and brings me coffee in bed. It's ready around 7.30. I wake up shortly afterwards, when people have left for their day of slavery, and use the bath.

However, apparently, this is not ideal. I have no idea why.
Shan

Hmmmm..... I can't think why either.... Rolling Eyes
Nick

http://www.screwfix.com/p/salamander-pumps-rsp50-positive-head-shower-pump-1-5bar/99043

This is pretty much what I have under the bath currently.
vegplot

Putting the pumps close to the tank will result in greater volumetric flow rates as pressures can be higher.
dpack

new pump next to the tank and remove the old one seems sensible
RichardW

Long term think about changing to a fully pressured system.
Nick

Long term think about changing to a fully pressured system.


Could you explain a bit more?
RichardW

Basically you are converting your system to work the same as a mains system.

I am guessing that currently you have a pump in the well that feeds a header tank that then feeds the hot & cold systems via gravity.

Instead of that have it fill a large (ours is 1500L & external) storage container that then gravity feeds to a booster pump & pressure vessel (ours is 100L) (with one way valve) that then feeds your house cold supply at mains pressure. Then that is fed to the hot water system so the pressure at the taps is almost the same for hot & cold.

How you would do it exactly would depend on how you currently heat your DHW. I guess you now have a vented hot water tank so would at least need to change that for a mains fed one.
Nick

I've always worried that the cowboy who put the plumbing in relied on it being low pressure, and cranking it up would provide more problems than it solved.

You're assumptions are right, tho, mostly. Our pump isn't in the well, it's in the house and drags the water up, pretty well, and shoves it into header tanks in the loft. Everything is then gravity fed, except three showers and baths, on these pumps at the end of the line.
dpack

upping the pressure might point out the shortcomings of various compression fittings,bad soldering etc etc ,a combo of low pressure and fur can hide many issues with pipes.sometimes just a bit of banging or sawing will show such problems as well.

the flexible nature of good modern plastic pipe systems might mean a full re plumb is possible and not too expensive if as i suspect the existing pipes have lots of sharp bends etc that might be the best long term plan.
vegplot

upping the pressure might point out the shortcomings of various compression fittings,bad soldering etc etc ,a combo of low pressure and fur can hide many issues with pipes.sometimes just a bit of banging or sawing will show such problems as well.


Don't let on. How on earth will Nick keep busy if he's not posting for help one issue at a time?
Behemoth

I suspect resolving one problem will reveal others that need sorting out. Plumbing's like that. Nick

If only because saying something's done encourages other people to add to the to do list. john of wessex

I don't know if you are familiar with the work of Porta, Chapelon et al but the phrase 'inner streamlining' comes to mind Nick

I don't know if you are familiar with the work of Porta, Chapelon et al but the phrase 'inner streamlining' comes to mind

Even google is unaware of that phrase. I'm a little lost, but you think I should get an Argentinian based steam train designer to fix my plumbing?
dpack

how long does it take to run a nice warm bath on a south american steam train ? Laughing
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