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Discuss Drop in shower pressure after new cold water tank install in the Bathrooms, Showers and Wetrooms area at

  1. Venger

    Venger New Member

    We had to replace our very old, round, cold water tank this week as it had split and was leaking thru the bathroom ceiling.

    Using some rudimentary maths and some online calculators, I worked out it had a capacity of approx 80 gallons.

    Having measured it, I new it wasn't going to go thru the loft hatch (I wasn't aware that you can fold them) so when talking to the plumber who I rang to do the job he said they'd put a coffin tank up there and a 50 gallon capacity would be more than enough for our needs.

    The job was completed yesterday and all was well until I had a shower this morning and there is a noticeable drop in pressure when using the main deluge fact the pump struggled to turn at all.

    The shower is an Inta Deluge Optimo, connected to a Showermate Eco S1.5 bar, twin, positive head pump.

    The main shower head is below the level of where the cold water tank is situated in the loft (it's in the same place as the old one) but it probably isn't a full 1 metre below but it never has been and there's never been a problem before.

    Have I massively shot myself in the foot by having a coffin tank?

    I'm assuming with the round tank having 80 gallons of water essentially sitting on top of the outlet that's connected to the pipe that feeds the shower, that's gonna give a lot more pressure than having a body of water that's 30 gallons lighter, laid out across 6 feet of coffin tank with the outputs on one end?

  2. Stigster

    Stigster Plumber

    The amount of water doesn't affect the pressure but the height or "head" does. The head is measured from the waterline in the tank to the outlet, a shower head in this case. Whatever height difference between the new and old tank's waterline is the head you would have lost. If your old tank water line was 1m above the shower head you were getting 0.10 bar pressure at the shower.

    If your new tank's water line is, say, 300mm lower than the old, you are down to 0.7 bar. As an example a standard Aqua Lisa thermostatic bar mixer delivers 7 Ltr/min at 0.8 bar. As you can imagine, a small change in head can make quite a difference especially if the original installation was marginal in performance for whatever shower valve you have.
  3. Stigster

    Stigster Plumber

    A low pressure shower mixer will improve things if the head is too low for your current model. Which shower do you have installed at the moment?
  4. Best

    Best Trusted Plumber Top Contributor!!

    I posted on the other thread that to check first if any valves are not fully open, like if an old gate valve was still on the pipework, or a restrictive small bore isolating valve.
    Also some crud could be blocking shower valve.
    I had assumed the reduction in head of water wouldn't make much of a diffence.
  5. Stigster

    Stigster Plumber

    Of course my comment is not relevant if the water level has not decreased by much. I was just considering that the current shower valve might have been working OK before but if there is a small loss of head taking the pressure below the operating limits of that particular valve.

    You are right in asking OP to check valve and strainers first.
    • Like Like x 1
  6. Venger

    Venger New Member

    Hi guys, many thanks for your replies and apologies for the delay in acknowledging them as I had to go out soon after posting.

    Stigster, from what you've said it's the change in the height of the head of water that's knackered me - if I'm measuring from the surface of the water to the shower head, then with the old tank it was definitely 1m, with the new coffin tank I would say that height has halved.

    I'm so bloody furious, solve one problem, create another.

    One thing I don't understand is the outflow from the tank drops out of the loft and into the shower pump which is located on the floorboards of the bathroom below, which is obviously a massive drop, this is then pumped into the shower, isn't the purpose of the pump to blast the water into the shower, shouldn't that make the height of the head of water irrelevant?

    If we didn't have the pump I could totally understand that we're completely at the mercy of gravity but I thought the pump would overcome this?

  7. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Does the pump run when you turn the shower on ?

    Also have the strainers been cleaned in the inlets of the pump ?
    • Like Like x 1
  8. Venger

    Venger New Member


    It didn't at first - however, moving the selector between the hand held head and deluge head, it did finally. When I switched the deluge head off midway thru my shower and then tried to switch it back on again it wouldn't until I went through the same procedure above, moving the selector between heads.

    I've never cleaned the strainers - how would I go about that?
  9. Best

    Best Trusted Plumber Top Contributor!!

    Now that you mention you have a shower pump, it is a different issue and not the head of water problem.
    I would have all filters checked and cleaned, plus shower valve.
    Also as Shaun said, tank could run dry.
    A 50 gallon tank might be only 40 actual
  10. Stigster

    Stigster Plumber

    He still has to have enough head for the water to start flow through the pump and start it working.

    Does the pump start when you lower the shower head as low down as possible?

    edit - just read the manual and only 100mm head required to activate pump so as you were!
    Last edited: Aug 11, 2017
  11. Venger

    Venger New Member

    Hi Best, thanks for the reply.

    Are you saying that we could run a 50 gallon tank dry with day to day use?
  12. Venger

    Venger New Member

    Sorry for any confusion altho I did mention we had a pump in my initial post :)
  13. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Put the hand held without the head on,

    Put it onthe tray as low as it can go

    Turn it on cold first let it run for a few minutes the. Turn it off

    Then again turn it on but this time fully hot and let it run for a few minutes

    Does this fix your problem?
  14. Venger

    Venger New Member

    Hi Shaun,

    I took the hand held head off the hose and laid the hose on the tray, I ran it on full cold for 3 mins and then full hot for 3 mins - both times the pump started immediately.

    I then put the temp back to where you'd normally have it for a shower and turned on the deluge head and initially, nothing happened, the pump didn't kick in and there was nothing coming out of the head but after about 5 seconds the pump started and water appeared at the head.
  15. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    I would say not enough water going through the pump to kick it in, easy terms two options

    One fit a negative head pump

    Two re install the tank higher same or higher than the old if you can

    These both are if there's nothing else at fault eg valve half closed etc

    To check the filters there should be some valves on the feeds to the pump (from your tank and cylinder these should be dedicated eg nothing else off them like your hot to your taps etc)

    To confirm that you've turned the right valves off open the shower with the head on the floor and give it 5mins if nothing's running after then your good

    Grab a big towel

    And undo one at a time the feeds to the pump (you might need a pair of grips / tools to undo the nut)

    You should see a mesh filter if it's got dirt clean this out most of them arnt removable (the filter)

    Then re attach the flexi and move onto the next inlet
    • Agree Agree x 1
  16. Stigster

    Stigster Plumber

    I know, my fault!

    The pump isn't getting enough throughput to reliably start so the issue is likely on the water supply side. It can be airlock but you got it running with some fettling, or the 50% loss of head has caused the problem but as I looked in the manual, 100mm head for the shower pump should be enough.

    Despite the head being enough for the pump, the only thing that has physically changed is the tank height. The draining of the old tank could have let debris block the pump or shower valve strainers.

    Does anyone else think the loss of height at the CWSC could cause this problem, maybe in conjunction with a partial blockage or restriction that is overcome when the pump finally kicks in? I say this because OP's pump kicks in when he increased the height difference between shower head and CWSC.
  17. Venger

    Venger New Member

    Hi Shaun,

    Thanks for the info - it is of course totally galling to think that after a fairly hefty bill yesterday, we may have to upgrade the pump as I don't really think repositioning the cold water tank is a viable option given that they had to add a fair bit of new pipework in order to connect up to the new location of the ball valve.

    I've just gone up into the loft and checked that the isolating valve on the pipe that feeds the cold water inlet on the shower pump is fully open and it is, although I have also spoken to the plumber this afternoon and he has said those type of values are apparently notorious for not fully opening when you turn them back on - he said he'll try and get over to us next week to check it.

    I understand the difference between a positive and negative head pump, I also understand that a positive head pump requires a specified flow rate of gravity fed water in order to start up and it seems that, given the change in head height of the water, this is causing the problem of the pump not starting everytime - what I totally do not understand is why, once the pump has started, I can feel a difference in pressure once I'm under the shower head ?

    Shouldn't the pump negate any difference in flow rate or head height once it's started, otherwise what's the point of having a pump on the shower in the first place ?!!

    Regarding cleaning the strainers/filters on the pump - I've actually dug out the installation booklet for the pump and in the exploded diagram it does show strainers and lists them in the key as not supplied, something the plumber who fitted would've had to by as an optional extra - only looking at the pump now, I don't think they're fitted.

    I've taken a pic of the diagram which shows them sticking out at 45 degress from the pipe and a pic of the actual pump and they're definitely not there.

  18. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Any chance of a pic of the new tank and take off for the shower also top to the cylinder?

  19. Venger

    Venger New Member

    Hi Stigster,

    Thanks for your input too.

    I've now dug out the manual for the pump and I note that it says on page 4, bullet point C, Minimum Flow : it requires a minimum gravity flow of at least 0.8 l/min through all outlets to be pumped.

    I can't seem to find mention of 100mm head though, what page is that on ?
  20. Venger

    Venger New Member

    Yes, you'll have to give me a mo to get up there again lol, d'you want a pick of the top of the cylinder too ?
  21. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Yes please take your time don't want any accidents
  22. Venger

    Venger New Member

    Sorry for delay.

    OK pics attached as requested. 20170811_185958.jpg 20170811_193437.jpg 20170811_193525.jpg 20170811_193927.jpg

    I have to say that I think I've made a massive miscalculation with regards the change in height of the head of water.

    When I looked at that last pic with the old tank in the background it really struck me that they didn't look that different in height, so I thought sod it and I spent a precarious 30 mins measuring carefully the heights of the tanks, where the water lines were/are, the height of the joists and the height of the new base...and what I've arrived at is that the water level in the old tank was 62cm about the ceiling height and in the new tank it's 52cm.

    So the million dollar question is would a 10 cm reduction in water head height be noticeable when I'm in the shower?!
  23. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Now answer this honestly did you install the new tank ?

    Doesn't matter either way

    Hope you don't take offence in me for asking
    • Like Like x 1
  24. Venger

    Venger New Member

    No! We paid what I consider to be a lot of money for a plumber to do it for us.

    Why d'you ask?
  25. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    It's a shambles honestly

    Tank base is laughable and no reason why it can't be lifted to a good height (he'll even 2' off the joists)

    Ptfe on the olives no need what so ever jointing paste at the most

    Hot outlet needs to be higher than the cold to the pump

    If I saw that would think a handyman has done it and not a plumber

    If you don't mind how much did you pay ?
    • Agree Agree x 1
  26. Venger

    Venger New Member

    Well, that's really cheered me up reading that assessment.

    If you don't mind, I'm not going to say what he charged us just so everyone can apparently have a good old laugh at our expense.

    You asked for the photos so I've provided them, is there anything in them that directly impacts the flow rate at the shower head?
  27. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    That's fine just for my benefit (so I could estimate how long he was there ) but all good

    Right flow question

    Pipe size
    Restriction eg non full bore valve
    Muck in the filters either at the shower or pump depending on setup

    If it's been working before you have three options

    Muck in the filters
    Pump on the way out / not enough flow through the pump
    Tank not high enough

    From the top of the rain shower head / hand held one which ever one goes the highest you normally need 600mm (60cm) to the bottom of the tank
  28. Best

    Best Trusted Plumber Top Contributor!!

    The vent pipe going into top of new tank is too low.
    I agree with Shaun that it looks a poor DIY job.
    Just needs a real plumber to check the flow going into pump and work backwards. I wouldn't trust the guy that installed the new tank to do anything though
    • Agree Agree x 1
  29. Best

    Best Trusted Plumber Top Contributor!!

    I hope there is an overflow pipe connected to the new tank and all sound and done correctly
  30. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Looks like a lead vent
  31. Venger

    Venger New Member

    You'll have to excuse my utter exasperation but 'real plumber'?

    As the end user, d'you know how hard that is to find?

    No one could recommend anyone, the local companies we phoned were saying anything from 1 to 3 weeks before they could come out so I resulted to the trade bodies which, according to the assessment of his work, aren't worth the paper they're written on (to mix my metaphors a bit).

    ...and apparently we still got shafted, so I give up.

    Night night.
  32. Best

    Best Trusted Plumber Top Contributor!!

    Yes, I noticed it seems to be lead and the feeds for to cold and hot are connected to lead I think. Time for a repipe soon.
  33. Best

    Best Trusted Plumber Top Contributor!!

    Sadly that's the way the trades are going, - plenty of diyers, handymen, builder types that claim they are plumbers.
    Then there are plenty of plumbers who really don't know the basics, or just don't care.
  34. Matchless.plumb

    Matchless.plumb Trusted Plumber Top Contributor!!

    Nowadays, the most people go where the money is. If it's carpentry , painting / decorating, electrical works whatever it is and they see the money they go for it. They do not care what's the end result, if they get called back for new works or if they loose some potential customers in future.

    There are only few which are taking pride in their jobs. I'd rather have 1 happy customer than 10 unhappy. It is very difficult to choose the right person for your own home especially if you do not know the things which are required.

    However, as shaun , Best, and the other lads of said he should seek another engineer to get that rectified and perhaps call the other lad back to discuss the problems and the paid money. I would not let him go like this. That's just botched!!!

    That's the reason why people don't trust anymore, if they get one installer like this next time you are there you will be not taken serious.
    • Like Like x 1
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