Combi boiler - pump options

sarkozy

We've had a combi system installed in our home during overall renovation. Due to practical constraints, it's located in our upstairs return where the old boiler was. There is a cold water storage tank in the attic (I'm told it's around 150 litres) feeding the cold taps in the bathroom. The hot water is running off the mains and must come in from the street, feed up to the boiler, losing some pressure. It seems that the mains water pressure is sufficient to run the boiler no problem (provided there are no issues) but there's no pressure for a shower.

For some background detail, the house is a 3-bed terraced house in Dublin city; one bathroom; and we're a young family (myself, the wife and toddler, and hope to have another). It's probably worth mentioning it's an old house, so I'm not sure how much weight the joists could take if an additional tank was added.

The problems are: (1) in the kitchen, the mains water pressure is knocking back the slightly lower pressure hot water from the boiler in the tap mixer; and (2) we have no shower pressure.

We've got three recommendations from two plumbers:

• The plumber who commissioned the boiler says we should install a submersible pump in the attic tank to provide both hot and cold pressurised water to the bathroom and hot tap to the kitchen.
  
• The plumber to plumbed the house says we should install a 'sump pump' under the stairs in the hallway to pressurise the mains water because that way, we have pressurised hot water everywhere and, he says, the attic tank doesn't fill fast enough due to local water pressure. I have not actually had this tested (flow rate, etc.).
  
• The plumber who commissioned the boiler also suggested, as a cheaper option, installing a shower pump only for the bathroom and place a restrictor in the kitchen tap to equalise the pressure in the tap.

I think I can see the trade-offs. On one hand, the attic tank may not be big enough as is and, with a quiet pump, we find ourselves running out of water after normal usage. On the other, we could have a big noisy pump in the hallway annoying us any time there's mains water being drawn through the house, unless the pump the plumber has in mind is very quiet (but I'm not sure whether to believe this).

We lived in the house for a couple of years before the renovation and had quite a small storage tank and very small hot water cylinder and it met our needs until we began the renovation.

What does anyone think?

(PS: I have read about this Salamander 'HomeBoost' which seems like a quiet way to boost mains pressure, though it may not be allowed in Dublin, which could help with the tank filling, but I can see why it would seem a waste installing two pumps in the house when one might fix the issue.)

sarkozy

Just giving this a bump. The issue is still current for us.

Update is: the plumber who fitted the system is still recommending a 'sump pump' (whatever that is) under the stairs as boosting mains pressure is required on account of the low mains pressure. In addition, he thinks submersible pumps in the tank are loud, often bang against the attic tank and still make lots of noise. To top it off, he won't tell me the actual kinds of pumps he would use. He's put it back on me to go ask people in plumbing supplier centres! It's his fault for not designing the system to take account of mains pressure to begin with. We might have built a small shed out the back to house the boiler in that case.

He then mentioned that we could wait until the water meters go in because that might lead to a boost in pressure! Who knows?

DGOBS

If the mains water pressure isn't sufficient to run the system or the combi-boiler correctly, the plumber who installed it should be brought back to correct this at his cost, or if not, then off to the small claims court!

As you correctly pointed out, HE designed the system and installed it, it's not your issue if it doesn't work.

sarkozy

The contractor will insist the plumber is not paid for the labour to correct the problem, but apparently I'm to pay for the pump. I would have assumed that the contract price for plumbing, which the contractor sub-contracted out, should have included all that was needed to ensure the system worked.

The plumber in question has continued to take a 'wait and see' approach, which the plumber who commissioned the boiler cannot understand. I can confirm that mains water pressure was an issue pointed out by the plumber right at the beginning of the job.

So, really, I'm stuck on two problems: who should pay, for what, and what is the best thing to do in any event?

K.Flyer

Is the cold water to your shower valve being drawn from the storage tank in the attic?

sarkozy

No, shower is currently 100% mains, which is currently partly why we currently don't have enough water pressure for the shower. have no shower. Bath, sink, toilet is tank for cold, mains for hot. Kitchen sink obviously 100% mains, but there's an issue with water pressure differential between the cold and hot feeds causing the boiler sometimes not to fire.

K.Flyer

Putting a booster pump on the mains may not solve anything.
If the mains water pressure is that poor, then there is not enough water to supply the pump and you cannot boost what you have not got.
Using the attic storage tank as a supply for a pump is fine, however you have two problems. 150 litres of water (approx 30 gallons) is really not enough to supply a booster pump for showers, especially if the mains is struggling to re-fill the tank. So a second tank will be required.
In order to utilise the attic tanks for your combi boiler and showers there is going to have to have some re-plumbing involved. That might be straight forward enough, because you say the boiler is located where the cylinder used to be.
I would also investigate the cause of the low water mains pressure and if I.W. are due to change the valve on the path, then that is your opportunity to get a new pipeline installed to increase the pressure.
In conclusion, my advice is this..
Minimum of 300 litres (60 gallon) of cold water storage in the attic.
Incorporate correctly sized quiet running water pressure booster pump taking its supply from the tank.
Re-alignment of pipework as required providing an adequate balanced hot / cold water pressure to taps and showers.
Cold mains feeds kitchen cold and tank only.
Avail of new Irish Water new mains installation to get a new mains supply pipe in place.
And let your main contractor pay for it as he is the one that brought in the installers.

sarkozy

Thanks. I'm thinking it might be a while until we get to have a shower. The plumber who commissioned the boiler, as I said, recommended the same as you have. I don't want to rush into a decision until more facts are in. There is still retention money due to the builder, so I won't be returning that until the issue is adequately resolved.

He may or may not be aware that the pipe feeding the attic tank also feeds the washing machine, which the plumber who designed and installed the system believes will cause us problems because the attic tank will not fill when water is being drawn by another appliance. I asked him yesterday if the half-inch mains pipe is adequate and he says it is. I don't know if this is correct. He is, as I said, also reluctant to install a submersible pump because it involves extra work and he thinks they're loud and would wake us up at night, as the tank is above our bedrooms.

It may or may not also be an issue for Irish Water, and therefore a timing issue for us. As you say, how could we pump mains water that isn't there? The mains pressure is not really, really low, but it's lower than it should be. Neighbours have said it was worse at one point before we moved into the area. Regarding mains pressure, I'll ask my neighbours again.

So it looks like we're still stuck and I may or may not have to have an argument. As you say, I was quoted for a system which isn't doing what it should, so perhaps you're right and I shouldn't be paying for the pump. Is this standard, acceptable practice? Because I get the impression from the plumber who commissioned the boiler that it is.

antoinolachtnai

I am sorry to hear about your problems. This is a bit tough, but the best thing is really for whoever designed this mess to put in something that is straightforward and is going to work for you in the long term., i.e., a conventional setup with a boiler and a hot tank and possibly a shower pump. From what I am reading, the plumbing in your area is just not suitable for the type of installation that has been done.

Unless the plumber who designed and installed your system has obtained a special permit from Irish Water or Dublin City Council, it was forbidden for him to install a combi boiler and both he and the person who commissioned the boiler should have known this. * Often, a combi boiler works fine. But if it doesn't work, then there is trouble, and Irish Water and the local authority have no responsibility for the problem, because it arose from bad practice by the plumber.

The plumber has designed and supplied something that is bad practice to the point of being illegal. Now that he discovers it won't actually work (probably because you are on a hill and don't have much pressure or else are supplied by very old pipework) he is expecting you to foot the bill whilst he tries to get off-site as quickly as possible.

If you leave him at it and allow him a budget, he will eventually find a way to make this work. The problem can ultimately be resolved by adding pumps and tanks. But this is a lot of expense, and if you end up with a tank and pump somewhere, it is an extra thing taking up space, an extra thing to maintain and an extra thing to go wrong. But the whole point of the combi boiler was that it is supposed to reduce the number of components that can go wrong and the amount of space that is required. So this could work, but it doesn't make much sense from your point of view.

Think about who is going to be responsible for maintaining whatever you come up with. Who do you call when something goes wrong in ten years time? The plumbers who are putting in this setup in barely understand what they are doing. How is some plumber in doing maintenance or emergency work to be expected to figure it out?

Putting a pump on the mains is another way to go at it. But a pump, like the combi boiler, also requires the permission of the city council/IW, which you probably won't get. If you do go ahead and do it anyway, it will quite likely work, but it could cause a problem for your neighbours. When your pump runs, it might effect their kitchen tap supply. There is a way around the legal and technical problem - having a 'break tank' at ground level to feed the pump - . But again, you are into more expense and taking up more space. Also, you are now storing drinking water in a tank and since it is at ground level and you have kids, you need to manage access to it. All in all, this has serious safety implications and requires special precautions way beyond what is usually required to run hot water to a shower and a few taps.

Some other bad options are being proposed to you in your original post. A restrictor on your kitchen tap cold feed will reduce the flow, certainly, but may not change the pressure very much. Flow and pressure are related, but are not the same things. I see two ways to solve this problem - use an appropriate mixer tap that will allow for different pressures on the hot and cold (this is the standard approach way of doing it in Ireland, where the pressure on tank-fed hot and mains cold are usually different in Irish plumbing) or else, somehow resolve the pressure problem so that pressure to the combi boiler is adequate (very awkward to do this, as discussed above).

Putting a pump on the shower (i.e., between the combi boiler and the shower) might work but does not seem a great idea. Pumps are generally good at pushing water, but not so good at pulling water. This pump would have to pull the water through the combi boiler from the mains and this would put a lot of strain on the pump. It would work until the plumber got out of the house, certainly, but it doesn't strike me as a configuration that any shower pump manufacturer would stand over (certainly not for a cheap positive head pump, for a more expensive negative head pump, maybe, though I doubt it.) It would also be illegal. For these two reasons, when the pump fails, you'll be on your own and it wouldn't be covered by warranty.

Getting a new pipeline from your valve/meter into your home isn't really going to change much unless there is plenty of pressure on the other side of the valve. So I wouldn't put too much hope in that possibility.

Whatever solution you come up with, make sure it suits you, and that the manufacturers of the equipment as well as the plumber and your main contractor are happy to stand over it. Since this is getting contentious, I would suggest that you make your grievances known in writing to the main contractor and get his proposal for a resolution in writing.

I am concerned that you are headed for a significant dispute with your contractor and you are going to have to consider how you will manage that.

*http://www.dublincity.ie/sites/default/files/content//SiteCollectionDocuments/Dublin_City_Council_Waterworks_Regulations.pdf - section 39, 59 (amongst others)

sarkozy

Oh great. More bad news. Because at the beginning of the contract, it was proposed by me to put the boiler where it is, but I specifically discussed at an early stage that plan's viability with the contractor and plumber and stated that if it is not recommended to do things this way, when we can consider alternative boiler placement options or use a different system, but the constraint here has been space in our home. The contractor had the plumber come out and inspect the house before beginning work and obviously did not voice concerns then. As I said, he said that he was aware of water pressure issues in the area, but he did not alter his plans.

At this point, I need advice on how to proceed.

I do believe I'm leading into yet another dispute and I don't want to be soft on them this time as the consequences are potentially hugely expensive.

I need more information, more advice, etc.

antoinolachtnai

It is really nothing to do with plumbing, it is construction mediation you need!

It may be that it is going to cost you some money to sort out this mess. That's not very fair, but it might be the easiest way to resolve the thing. And at the end of the day, your family probably desperately needs a working bath/shower as quickly as possible.

If you have a written contract with your builder, you should look carefully at that. However, you want to avoid any talk of litigation, etc. Litigation at this level of spend would be a disaster. Some genius will no doubt suggest the small claims procedure to you, but you should not attempt that without legal advice (there are serious 'gotchas' if you litigate over a construction contract, particularly an unwritten one). I wouldn't bother throwing the book at him on the rules, the water pressure, etc. in writing, but I would gently mention these things to him when speaking to him. It is up to him, not up to you to come up with the solutions.

My suggestion is to put a polite but firm statement of the problems in writing to your contractor and ask him to write back to you with a statement of the causes of the problems and the solutions he proposes. I would also speak to him at the same time. I would speak gently and calmly, but firmly.

If your plumber and builder really are clueless, one technical solution that strikes me is to put a hot tank in the press beside your boiler, and plumb the upstairs bathroom to that. You could still plumb some downstairs hot taps to the combi if that was any help to you. The hot tank would be plumbed into your new boiler using zone valves or a three way electrical valve. I have no idea if your press or wherever your boiler is would have space for that. Putting a hot tank in the attic is tricky, because it has to be at a lower height than your main water tank, but it might be a solution. You could put your shower pump at a lower level so you didn't need a negative-head pump.

If you could source a 'rapid recovery' tank (one that heats faster than a regular tank) you might be able to make do with a smaller than standard hot tank, because it will only need to feed one bathroom. You can get tanks which are narrower than normal tanks. These are not 'standard issue' that they have in stock in Chadwicks or Heat Merchants, but they can be gotten. (See http://www.coppercylinder.co.uk/gledhill-indirect-hot-water-cylinders.html for an example)

A specially-sized rapid recovery tank, a three-way electrical valve and some sort of timer/controller would probably cost you about 700 euros going by those prices. It is really not that much if it actually solves the problem and the contractor is prepared to take responsibility for it.

There is a technical reason to do with the way condensing boilers work why this is not an optimal solution energy savings-wise, but you probably aren't worried about that at this stage.

One useful thing you might do is to contact the distributor or manufacturer for the boiler. They generally have help desks which will be able to provide some level of advice, if you have a reasonable idea what you are talking about yourself. They may even have someone who can call out to have a look. They won't tell you much you don't already know, but at least you will have someone to back up your position, i.e., that something is seriously wrong with the installation or that the product is unsuitable. They might be able to suggest some technical solution too.

sarkozy

Thanks. The plumber who commissioned the boiler, which is a Worcester Bosch, and who it registered with them, seems to think the system is OK, but the attic tank does need storage. However, I'm not sure whether or not he fully appreciates the water pressure issue. However, a little Googling turned up good things about this plumber, and when I spoke to him, he seemed extremely competent and knowledgeable. The way I feel at the moment is that, (a) due to us not having a fully functioning system as we should be getting, I want the contractor to agree to (b) get his second opinion on a way forward and possibly another recommended plumber's and (c) have them pay entirely for the work and materials required as this should be their full responsibility.

The problem for the time being is that they still have work outstanding and I think it wise to ensure they complete this work prior to engaging them on this issue in case the dispute negatively impacts on the outstanding work.

antoinolachtnai

The person who commissioned the boiler is putting forward a valid way to resolve the problem. (You said above that he recommended putting a pump in the tank in the attic.) I take it that he is proposing that you feed the boiler from the attic tank instead of the mains. That will require a pump. That will certainly solve the pressure issue.

The issue is that it involves more tanks and an extra pump. That will work, but it will make the system complicated for a fairly small house and may also make it noisy. (see for example http://www.boards.ie/vbulletin/showthread.php?p=75599274) A good pump is also not particularly cheap and installing a pipe from the attic to the combi boiler may not be particularly easy. (You are quite right to leave the job of specifying the pump to the plumber by the way.)

Remember, if any of this stuff goes wrong in the future, you will be completely without hot water. And you will still need a solution for your kitchen tap, because there will be two different pressure levels, one from mains and one from the pump. (This is why having an unpresurized tank with an immersion is such a popular and good solution.)

antoinolachtnai

One other thing - you might be able to get the commissioning plumber to come along and make technical recommendations, and help the builder come up with a solution. He will not want to side against the builder, but it is good that there is at least one person in the job who knows what he was doing and whom you have confidence in.

sarkozy

My thoughts precisely. I was thinking of asking the contractor, who has some kind of working relationship with this guy, to come out, inspect/test our system and make technical recommendations which the plumber who did the job will follow. I don't know why, but this other plumber has my confidence, and it's he who said to expand the attic tank capacity and to install a submersible pump in the attic, but he'd need to investigate more first.

He seems to be the sort of plumber who really believes in being straight about things and doing the best job possible in each situation.

Let's put it this way: the plumber who set out the system is putting it back on me to investigate what pump to use. This is not good enough. I'm not a plumber and I want confidence in the plumber who solves the problem we've paid to avoid in the first place.

antoinolachtnai

Make sure that having a pump in the attic is really the best solution *for you*. Make sure you fully understand the implications. Adding a hot water cylinder might be more suitable (and cost around the same).

The commissioning plumber is in quite a difficult situation. He wants to avoid 'dumping' all over the main plumber and he wants to keep on the good side of the builder. At the same time he wants to see you sorted out, for the good of everyone.

sarkozy

What would be bad about this attic pump option? I'm also not sure there would be space for a cylinder anywhere in the house. This is where I begin to get anxious because I literally don't know exactly what the pros/cons or implications are.

antoinolachtnai

The problem is the complexity (another thing to go wrong, and if it fails, you're in big trouble), the expense (maybe not your problem, but somehow it will be an issue) and the noise (any time you run the hot or cold water or flush the toilet, there is going to be some level of noise from the attic. I really don't know how much.

This is the sort of thing, and price, you're talking about - http://www.rvr.ie/default.aspx?subj=catalog/ProductDescription&catIdPath=0_44_64&productId=ACW110

If you get the more experienced plumber in, he should be able to talk you through the options and the upsides and downsides much better than some randomer on the Internet!

sarkozy

Thanks, this helps immensely. I agree it ads more expensive complexity to the system, but I'm thinking it's one of only two options.

Alternative set-up, but could this be another way of going at things from the attic? http://www.rvr.ie/Products/SWH499/0_44_20/ (Assuming doubling tank capacity and lifting tanks to a position above the pump, with the pump itself fixed in a way to lessen vibration noise/) I'm not sure what decibels the system you linked to produces, but the link here suggests the pump is roughly as loud as as our fridge (for comparison, the quietest pump I've come across, the Salamander HomeBoost mains booster) is rated at 46db, and our dishwasher is 47db, which we hardly hear with normal background noise.

Can I ask if there's also a way to reduce potential for the 'plopping' sound an attic tank makes when filling? I have already mentioned to the contractor and main plumber about lifting the tank and installing some heavy insulation/PIR board and neoprene beneath the tank. The plumber has, for the most part used flex pipes, which I've read helps improve matters slightly.

antoinolachtnai

Have you got a lid on the tank? Some sort of cover on the tank will make a difference. In this day and age all tanks should have lids on them anyway. There is a thread on it here. http://www.boards.ie/vbulletin/showthread.php?t=2056541976

You don't want to have a whole lot of insulation under an attic tank. The reason is that you are depending on ascending heat from the house to stop the tank from freezing during a cold spell.

antoinolachtnai

Yes, you could use that sort of pump in the attic. But it is not submersible and pretty expensive! A friend of mine has something like this fitted. 65db is a good bit of noise from that pump. The idea of the submersible is to reduce the amount of noise. I wonder can a pressure vessel be fitted to it? Really, you need to talk to the plumber about the options.

Surely you can find somewhere within the house (under the boiler perhaps, if it's not in the kitchen) where you could fit a 1-foot diameter cylinder?

sarkozy

The tank has a lid. I think that pump can take an expansion vessel, I've seen videos about it before where one had been fitted to it.

It may be possible to fit a cylinder in the hot press below the boiler, but I wouldn't hold my breath, and this would also be where the washer and dryer are. That's a lot of heat in a small space.

Thanks for the link, I've read that thread before. So no way to lessen the plopping sound ...

antoinolachtnai

I have to tell you, if you like the plopping sound, you're going to love the pumping sound!

If the attic is well insulated and the attic door is well sealed, I wouldn't think you should hear much (at least that's my experience with the noise.)

The heat off a well insulated tank isn't really that much. Maybe there is somewhere else you could put it.

Main thing is to consider all the options and pick the best one.

sarkozy

The attic is insulated between the joists, half the attic is floored with PIR between the joists, and the attic door isn't near the water tank and is quite well sealed. It's just that the tank is resting directly on the joists. Beyond that, the ceiling below the tank is lath and plaster, and plasterboard slabs below that (it's how it was when we moved in). It's also not the room we sleep in, just the kiddie's room, and I think it's unlikely we'd be having baths/showers and going to the toilet at night (number 1's).

But you're right, I want a competent plumber to set out options, pros and cons and to set out a plan and agree who's paying for it. We are where we are.

antoinolachtnai

In my last post, I was referring to my experience with the plopping noise. I did have this problem before, but doing all the things described really dealt with it for me. That said, it was a plastic tank. A metal tank might be a different story.

The plumbing noise, now that's louder.

Your approach sounds very measured and sensible.

mugwumpjism

Hi Sarkozy,

Did you ever get this issue resolved? I have similar problems but doesn't seem as bad. My whole system runs off the mains and I have a shared water supply with my neighbor, i.e. we have one pipe off the main road pipe that splits just before the front doors. The pressure in the shower is very average at best and drops off if someone turns a tap on or the dishwasher or if nextdoor is using a few appliances. Also in the mornings the pressure in the area as a whole seems to be down. I am looking for solutions to boost the shower pressure, I do not want a nosy pump and will pay for a quite one but I need to know what option will work best? Splitting the water supply, pump for the whole system or pump for the shower only.

If you found a solution or anyone has ideas they would be gratefully received.

Thank you

mugwumpjism

I forgot to mention it is a combi boiler and the house was replumbed from scratch 2 years ago