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Question DetailsAsked on 2/4/2017

What is the cost of replacing a circulator pump on my old boiler?

The circulator pump is dripping water.

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1 Answer


I am going to address this as a circulating pump on the main water pipe leading to/from the boiler, inside the boiler metal outer housing - but very similar if an in-line circulting pump external to the boiler housing escept some of those are pipe threaded rather than flanged connections - both are common.

Wipe it off (beware - typically about 160-250 degrees depending on model and if water or steam) and look where it is dripping - if coming from the pump housing or motor (which sticks out from the pump at 90 degrees) rather than at the end flanges, then normally the pump portion at least needs replacing. Some brands like Taco the motor can be detached and if not damaged by the leakage only the pump itself needs to be replaced - commonly about $30-60 for the part retail, more like $100 range if provided by the plumber as part of his service call. Motor replacement is pretty common - they typically run for 20-30 years or more, whereas the pump can wear out in a decade or two if the water is dirty or corrosive. If pump and motor both have to be replaced or should be becasue the pump is wearing/corroding up, or the pump-part only not readily available or more expensive in labor to go get, the total pump/motor unit is usually about $80-250 retail depending on model (say commonly $150-400 from plumber) unless you have a long run or serving multi-unit building or high-lift system needing about a 1/4HP pump rather than normal about 1/20 - 1/25th horsepower one, in which case more like $200-450 retail/$300-600 plumber charge would be more normal parts range. Labor unless access if very bad - usually minimum service charge visit of 1 hour or less so typically $75-300 range, most commonly in the $150 plus or minus $50 range in much of the country. About same for pump only or total unit replacement (usually 12 hour or less work, commonly more like 1/2 hour with good lighting and access), and not much less if only the gaskets need replacement.

If it is leaking from the gaskets connecting it to the piping (usually bolted into the piping at "ears" or lugs on threaded pipe fittings and the pump housing at each end) or at the bolts (which would still be from the gasket usually) but NOT coming out of the pump/motor housings or the motor itself, or from the pipe threads which the mounting fittings connect to the pipes with, then usually just new gaskets or redoing the threaded connections are needed - again same minimum service charge, but parts only a few to maybe $15 depending on whether the bolts are corroded and need replacing too.

Sometimes if the threads for the flange fitting are leaking it is indicative of serious rusting there - so sometimes the flange fitting and/or adjacent pipe of pipe need replacement too - which might add $50-100 typically to the cost if they are corroded and a pain to break free.

If leaking at a gasket and the gasket/seal is fairly new - say not more than 3-4 years old, many times just carefully tightening the nuts on the bolts (just good and snug, do NOT reef on it or you can break the lugs off - and tighten both sides alternately, not one side totally then the other) will handle it. This sort of leak also very commonly occurs when the boiler is turned off and cools all the way down, loosening up the connections so they leak - in many or most cases where that happens, they dry up again once the boiler heats back up - partly because the connections tighten up, partly because it gets hot enough that very minor leaks just evaporate away, leaving just a mineral residue behind at the leak point, though of course that point is susceptibel to future leakage should ber replaced at least at the next routine mainteance. If the gaskets are older, tightening them can cause it to turn into a MAJOR leak, because the gaskets get brittle with age and disintegrate when tightened - so unless prepared and able to turn the boiler (and its inlet water) off if the gasket disintegrates or prepared with new gaskets and able to DIY, I would not try tightening them unless the gaskets are quite new.

Plumbing is the normal Search the List category for this - in some areas Heating and A/C contractors are the primary repair people for all home heating equipment, whether water or air is heated. Many HVAC companies do both in most areas.

My recommendation - if you have a choice, tell him you prefer the red "football" gaskets rather than the O-ring type - they conform better to older slightly corroded surfaces (which should be well wire-brushed before reassembly and coated with permatex sealant if not smooth metal after cleaning) as in my experience they last longer. Also - the football gaskets stick out around the joint, so easy to flex them and feel if they have gone hard (typically about 10-15 years due to the boiler heat) to see if getting near time to preventatively replace them (DIY or at next servicing).

My recommendation if total pump unit needs replacing - Taco brand.

Remember the motor runs on 110/120 V power so be cautious in wiping it off to see where the leak is originating, AND all the piping will be hot enough to cause serious burns with very short contact time. Also - commonly the transformer and commonly the low-voltage wiring is exposed in there, so watch out not to short anything out - obviously best to have it off when doing this, and I double-drape rags or towels over the electrical components in case of water spillage so they do not get wet.

Note on motor replacement if DIY'ing it - many brands it does not matter which wire is connected where on the motor - but on some miswire it and the motor housing can become "live" and instantly short out, and on some brands it does affect which way the motor turns so wire it backwards and not only will the water move the wrong way, but very ineffectively because the pump rotor is designed to work in only one direction. So keep track of which connection the live wire was hooked to. That can be a heck of a thing to diagnose when one is put in wrong that way. Note also there is a definite flow direction for the pump (marked by an arrow on the housing casting) - turn it around and it can mess a bunch of things up, as well as (depending on location) potentially pull a lot of bottom junk out of the bottom of the boiler thereby shortening the life of the pump and jamming zone valves.

Answered 3 years ago by LCD

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